OK. Now could a vacuum line broken to this EGR valve cause a hesitation upon accelleration when the car is warm and other problems ?

Did you say it ran better with the vacuum line disconnected?

It ran the same which was basically because I was doing highway driving and engine never gives me problem on highway or when engine remains cool.

Then today I put on new hose to EGR valve and drove around for 40 minutes in city traffic . Up hills and not a stall at all . Engine temp got to 98C and I drove up a 15% hill to really put it under load and it drove fine.

Then I stopped for a cup of coffee and after 15 minutes started her up and without waiting 30 seconds, pulled away on a flat road, and it hesitated again at 84 Celsius . Drove for another 5 minutes and did not happen again .


Stopped for a half hour and then drove for another 10 inutes No problem again.

Stopped for dinner about 80 minutes and then drove it around again for another 10 minutes (temp near 80 C) no problems. Any way the EGR could have caused all my problems ?

Anyone think the hose to the EGR all by itself , made it better and the computer has to relearn something thus the one time flat spot/ bogg down ?

If so , which I hope is true, it cost me $700 for a 50 cent piece of hose!

This may help you to understand the EGR. It's #7 in the link below.

Emery please read my above post #53 which I have edited. My problems were not inspection emissions related but much more serious hesitation/ stalling problems that at least for the moment have improved tremendously, or gone away completely . ( I say this after only 5 quick trips , with one appearance of the problem)

Simple question is can a broken hose ( loss of vacuum ) to the EGR cause those types of problems. Can anyone answer that question and no more info needed.

I think you found the "something simple".

I think it's possible, but you said that the problem hasn't entirely gone away or maybe not sure it's gone away. Maybe it's something entirely different like the ignition coil going bad. You're not getting any DTC's at all?

I can't see how this would cure it completely. The EGR is only active under part throttle conditions anyway and that vacuum line is not big enough to cause a big enough vacuum leak to cause your symptoms. Report again after you have driven it on a longer trip and with higher engine temps.

I have to ask: Are you sure you were in a truly dark area when you looked for the arcing? It has to be pitch black. My spark plug wires on my 93 400E were in very bad shape when I bought the car 4 1/2 years ago with about 125,000 miles it. They were arcing and the car ran poorly when one asked for acceleration from it (like yours). My 95 E420 had about 170,000 miles on it when I got it about 3 months ago and it's wires are absolutely rotten. I do not believe your wires could still be good if they are the original ones. Has it been established for sure if these wires have ever been replaced or not? It is a common misconception that these MB spark plug wires don't go bad because they are solid core (as opposed to carbon core wires which do go bad much more frequently). But even these solid core wires go bad because the insulation somehow for some reason slowly stops "insulating". I don't know why. I don't know if it's age related or miles related or both. Don't discount the spark plug wires yet.

Another thing I'm wondering about now is the engine wire harness. It is a known problem of MBs of that time period. The insulation of the wires literally turns to dust but it's difficult to spot because the areas where the wires are exposed look fine. It's the areas that are the most hidden where the rot is the most pervasive. I think it has something to do with the fact that a more hidden area will keep moisture longer. This would need to be checked out by someone who is familiar with the problem. Maybe a member of this board who lives in your area can help you check this out.

The good thing about both of my suggestions is that you can check and see if you need to replace these FIRST, without having to buy anything unless you confirm that you in fact need to.
Regards, Eric

I just wanted to make sure I understand what you're saying here. When you turn your key to position 2, you do not see a check engine light?

When I turn my key to position #2 I see every light on the instrument cluster light up, but none of them is a CHECK ENGINE LIGHT. There ia a light for ABS,BRAKE, ENGINE, COOLANT, OIL, LIGHTS, SRS, ASR and a few more that I do not recall .

There are a total of about 9-10 lights that all are working but no one light specific for CEL .

What would it look like and what would it be called . I do not believe there is any more room on my instrument cluster for any more lights , and all the lights there work

.

I drove to the country to check. We pulled the wire covers off and looked at idle , revving under load, when warm , NADA. My dealer mechanic had checked them and changed 3 suppressors but in his opinion the wires were ok


A mechanic in another forum PMd me this comment in regards to whether the EGR valve could be causing my problems and I quote him


"Of course.... the Exhaust gas recovery system can cause havoc with the Intake and idle/acceleration, especially with a sufficient leak to ambient pressure and temperatures... remember the gas recovery system is trying to pump the recovered gases back into the intake for extra fuel economy... this can especially foul up the air/fuel mix... perfect is .460 volts (actually called 460 milli volts) not rich and not lean....
But actually falling into Lean territory due to emission standard... but the leak throws it off and really fouls up acceleration and cause missing and stumbles..

Good Job! Great diagnostic effort... kudos all around for you! Hope you feel good! You never gave up... keep a close eye on those vacuum 1/8" vacuum rubber lines connecting the 1/8" nylon color coded lines... all extremely important as well as the secondary air injection system and Exhaust Gas Recovery valve and tubing as you have discovered... all are important and I cannot stress this enough... ALWAYS keep eye on these systems for maximum performance! "

Its really difficult to believe a 50 cents piece of hose could be the problem, after spending $700 on 2 mechnanics and parts.
I only hope he is correct and I will be driving around the city today 2-3 times and I will post back my results. Time will tell

I have not checked for DTCs but my Dealer mechanic said it showed no codes. Maybe I should make that reader and not beleive mechanics any more

When I turn engine to position #2 I see from left to right HIGH BEAMS, BATTERY,WASHER FLUID, RADIATOR, OIL CONTAINER , LIGHT BULBS HEADLIGHTS ETC,

Then on the right hand side of cluster ASR, ABS, A CIRCLE WITH BRAKE DRUMS AROUND IT BRAKE LINING LIGHT,PARKING BRAKE,SRS, SEAT BELTS, for a total of 12 lights believe there is another on top in center for ASR indicator .
There is a triangle with an exclamation point in the middle of it , in the cluster above the center where it says MPH not a ASR warning or it may double as an ASR warning as I remember seeing something when driving in snow

Is this what you are referring to as a Check Engine Light ? I am not familiar with what it looks like. In my wifes Mazda it is an engine bock that flashes

No CEL

Well Eric you are right again. I drove this AM for 30 minutes and it drove without a hiccup. 2 hours later I took it for another extended city drive and it takes 25 minutes or more to get to over 80 C. Then i drove it up a few hills and it stumbled again albeit for a much smaller period of time.

It seems to be getting better and maybe something in the gas is causing these problems like someone stated. How long should it take in city driving to get to 80C. If I get on a highway ,temp drops back to 70C. Is this a sign of something bad. I just had my coolant flushed and refilled with Benz coolant around september .

Just remember this car only has 83K miles on it and a dealer mechanic who looked it over for 2 hours , thought the wires were fine when he changed 3 suppressors and 8 spark plugs

Tomorrow I am going skiing and its about a 70 mile drive. My first experience with the problem was after a highway drive and then getting into stop and go driving .

I will replicate those conditions tomorrow two times, and report back .
I guess it was wishfull thinking that the broken EGR hose could have been the source of all my problems . Grrr

I think you should be able to see the writing on the light cover without the key being on. I just checked mine and I can see it. It should say Check Engine. Mine is all the way to the right. I can't imagine yours not having one. https://docs.google.com/leaf?id=0B-WRh0Hf7VdZMmQ3YTgwYjUtYTRkZC00YTY2LTk2YWQtNWM4NmY3N2E5OGZh&hl=en


It is possible that the prior owner disconnected the light and tried to hide the lens cover. Build the code reader and see what codes you're getting. This may point you in the right direction.

The large variance in highway to city temperatures are likely caused by a failing fan clutch. I have replaced a few. Here in the desert, there's no such thing as a "close enough" repair to the cooling system. Every part is tested in normal driving every day and it has to be perfect, including the radiator cap.

As for the hesitation and stumbling, I, like Eric400, would be very suspicious of the engine wire harness. Not the spark plug wires, but the engine wire harness. I think 1993-1995 were the affected years for this biodegradable insulation, which if I read correctly somewhere else, was the doing of the German government environmentalists. Yippee for government intrusion!

But I digress. Any time I have suspected wiring issues, I, if possible give the harness a push/tug while the engine is running. If there's a problem, it'll likely show up. The reason I'm suspicious of this is not just the year, but the symptoms. If the harness is bad, get out your wallet.

Also, when checking the plug wires in the dark, even if you're under a street light, the dancing voltage can be seen and is more likely to show up if the high tension (spark) wires are introduced to moisture. What I have used in the past is mother's plant spray bottle. If you don't have one, I'm sure you can pick this up at your local Wal-Mart. With the engine running, simply spray the wires with a fine mist of tap water and look for the dancing arcs. If they're not there, its not your problem.

I think 1992 was the last year for CIS-E, but I'm not sure. If yours has a different style fuel injection system, then I don't know much about it. However, one question came to mind as I was reading through this entire thread was; what about the throttle position sensor? If it has a dead-spot, then wouldn't that cause an issue?

Fuel additives do little to curb this kind of hesitation/misfire, but do wonders to the upper cylinder and valve area inside the engine.

Moisture (water) in the fuel is a possibility, but unlikely to be consistent and RPM specific. Though it wouldn't hurt to drop a bottle of HEET into the tank every now and again, just for peace of mind.

That's about all I have to offer. Good luck!

My cluster is different from the one you posted . In the far right of the cluster is a seat belt icon and the light bulb icon is on the left side of the cluster . I listed them in exact order from left to right and mine has ASR first and I cant see what yours has there due to flash .

Your right side does not have the same order as mine that much is certain . Oops I just saw yours is and E series and mine is a S series so yours has a different cluster .

I have to make the code reader if I cant get my mechanic to draw codes. When I told him caps and rotors did nothing he siad bring it in tuesday for him to check out , he had some other ideas .

I assume the scanner he has , will draw the same codes as the LED I should make ? Correct? Or is the LED better ?

I think the dealer's scan tool is much more sophisticated, but does not give the codes as we DIY's know them (the number of flashes on our LED testers). I was talking to my tech about a DTC 19 and he looked at me like I was an alien. Apparently theirs tells you in English what's wrong. You should keep looking for your check engine light though. It's got to be there somewhere--even if it's an S-Class.

Here's a link to Jim Forgione's home brew tester. Scroll down to the bottom of the page.. http://www.k6jrf.com/MB_X11.html

The thought just occurred to me: have you checked to see whether you have an aux diagnostic X11/21 switch with LED in your engine compartment, like the one in the picture in the link above? At least you could check the Diagnostic Module codes with this.

Spark plug wire arcing will not be visible unless it is totally pitch black unless the wires are really bad.

Your M119 W140 is definitely a LH-SFI not the CIS-E. Same would be true even if it was a 92.

While you are on Jim F's site, you should read about and then do his "cool harness" mod. He tells you how to do it yourself (It's very easy) or you can buy his plug in kit. I swear by the mod and many guys who are way more knowledgeable than me swear by it too.

California cars got the self diagnostics system and the "Check Eng" light that goes with it before the rest of the country did so it's possible that your car didn't come with it especially if your car is an early 93. All 92 and later 500Es supposedly got this system regardless of whether or not they were Cali cars but my buddies 92 500E doesn't have it. It is an early 92 BTW. The point is if your car doesn't have it, it doesn't mean something is wrong.

Another crazy thing that has popped in my head is the possibility that the cats are beginning to plug up. I don't think this is "it" but it's something to keep in the back of your head if all else fails.
Regards, Eric

Ok I am going on this one day ski trip today which will only cause the same problems anyway.Grrr I am going to make Jims or one of the testers I have instructions for a Radio shack version and I positively do not have the LED light in mine , it should be right next to the CAN and I have checked 3 times .

I will wait till engine is really warm to test, as I am quite certain dealer mechanic did not wait 25 minutes for engine to get up to 80 + Celsius when he ran his tests.

Thanks

P.S. By the way did you find Jims air conditioning page . I had printed it out about 5 years ago ,and I cant find it now in my bookmarks or on his site .

He had the DTCs you could get my manipulating the buttons in certain positions at certain temps . That is what I have been using for my coolant temperature reading, which is more accurate than guessing what the cluster gauge says ( I HOPE )

This sound like degraded fuel, we see this a lot. Runs ok at lower rpms, then when asking for more, they stumble...

The original poster and I have the same car, NO Check Engine Light. I believe it only exist with California Models with the Diagnostic Modules.

thx
chedeng

Well I am glad we cleared that up . Chedeng I have Pmed you .

Here is todays diary entry Grrr

Well I just finished my skiing day trip. First of all engine temp stays around 71 on highway. At good speed without traffic (55-65 MPH with outside temp 1 C ) stays between 67 to 71 . After getting closer to ski mountain drove at lower speeds for about 25 minutes , the traffic for a few minutes and temp got to 82C and then a couple of stop and goes and got no stumble.
I was in a rush to ski so I did not do excessive testing.

On the way back to city, engine temp stayed around 70C on the road ,in the city it got to 98C and then stumbled at 1500 RPM. Then I drove to a small hill with temp of 99C no flat spot.
Went around again to same hill at 96C stumbled for a fraction of a second.
Maybe this is off the wall , but should temp be that low at highway speed 70 C and then fluctuate so quickly to 98C when I get into city traffic, and then drop to below 70 on the highway again. If not could this be sending some wrong signals to some sensoors ?
I have never had an overheating problem till this summer when coolant low sensor went on, but car temp never got to RED line in brutal heat.
Could a fautly temp sensor cause any problems like the ones I have? Or a thermostat or anything not ignition related but more cooling system related. I have been monitoring engine temp like a cardiologist monitors blood pressure etc , and maybe there have always been these fluctuations , and I am first noticing them ?
Bottom line is the stumble/hesitation when over 80C is still there , but not as often nor as severe.

If your freon is low, it will cause the low speed fan not to come on when the temp starts to creep up (in city driving). It sounds like an unconnected issue though.

update
 

I just went out and drove around in this storm with the car both cold and warm. On flat spots and up hills. Both feathering the throttle and mashing it .

First of all the car NEVER stumbles when cold , under load (hill) aggressively, under load (hill) practically full throttle , under load (hill) feathered throttle like pressing on an egg etc., on flat ground under all conditions imaginable, IT NEVER STUMLED COLD !

It also idles perfectly regardless of temperature.

It stumbled one time when warm (over 70C) and stumbled fairly consistently once it was over 80C when I tried aggressive acceleration, over flat ground or hills . The more throttle I gave it te more likely to stumble. At WOT it took 2 tries to get the engine up to speed .

There are 2 constants , that can be considerd constants, as part of an intermittent syndrome in my mind .

#1 It will never stumble COLD regardless of throttle pressure .
#2 And it will not stumble loaded, unloaded , hot or cold , as long as I feather the throttle.

Someone suggested the fuel pressure regulator because it only happens when I try rapid acceleration , and that takes more vacuum . Does the amount of vacuum vary with engine temperature?

When I say cold, I mean from first starting out with engine running less than 45 seconds in 35 degree outside temp (below 40C bottom of temp gauge ) straight up thru approx 70 C .

And if it stumbles on quick start at 70-72 it is only once in ten tries.

What varies exclusively with temperature. I do not know at what engine temp car goes from open loop to closed loop but I think that at 65-70C after 3-4 minutes of driving it is prolly closed loop.
Still no problem till it hits at least 80C usually. And the hotter it gets , the more likely it gets that it will break up on hard acceleration, regardless of hilly or flat.

And why regardless of everything else, very light feathering does not create a problem ?

I asked the new mechanic again today, and he said he pulled the hose on the fuel pressure regulator and said it was OK. I think he said it did not leak . Does fuel pass thru it ?

Any new theories anyone ?

My mechanic is tryng to locate a used injector rack to throw on for a test

When you say "stumble," do you hear anything that sounds like preignition when it's under a load? I'm talking about what it commonly referred to "valve ping."

I mean a flat spot, miss, stall, hesitation almost die out.I dont think it is anything like a ping from using lower octane gas, or bad timing etc.

It can vary from almost a hiccup , to feeling like the engine stopped completely for one second or more, if I do not back off on the pedal . It varies according to how aggressive I am on the throttle.

More gas when it happens, it almost dies totally. Less gas it hesitates/sputters for a shorter period of time. I think I just instinctively back off on the throttle when I feel it , so as not to cause any damage.

Feather the throttle and no problem whatsoever. I have become very proficient at feathering, and could probably drive witout breaking an egg on the gas pedal.

The few times I tried to power thru it by giving it more gas, the engine just felt worse and nearly died completely on me.

Do you get a puff of exhaust smoke when you start it after it has been sitting over night?

Now that you mention it , my first mechanic out of certified MB mechanics thought it was coils. His partner said caps / rotors. I replaced caps/rotors and plugs plus 3 suppressors .

Maybe I should change coils. They are not very expensive to do?

I wasn't really thinking coils. On my old 400E, I had a problem where the engine was severely pre-igniting under a load and it did not have any power at that time unless I backed off like you were saying you had to "feather" the engine.

It always occurred when it was up to temperature and under a load. What I think was happening was that the valve seals were leaking oil into the cylinder after I shut it down for the night and the oil was coking up on top of the pistons. Once the engine got up to temperature, I think the deposits were causing an independent source of pre-ignition. The ignition module has the authority to retard the ignition if it is pre-igniting and it will result in a loss of power like you described.

The good news: I ran two quarts of Chevron Techron through one full tank and it absolutely cured the problem. I couldn't believe it. I thought I was in for a new engine, but the Techron totally solved the problem.

It was either the coking of oil on the cylinders or a clogged injector that was leaning out and causing detonation. In either case, it is very cheap to buy this at Costco by the 4-pack. Make sure you changed your oil after you run through a tank full. Maybe it's not the problem, but it sure is cheap to find out.

I have run 2 cans of Techron thru in the last 2 tankfulls of gas. I am running a Lucas additive that is supposed to clean injectors as per my mechanics instructions.

But what you are describing is what my hesitation/ flat spot feels like. I have never looked at the exhaust when I first start it up in the morning , but from inside the car I have never noticed anything like that .

I will look when I start it tomorrow . Would I not be low on oil if I was losing it thru valve covers. I will check that also ,as I never check my oil level between changes , only when I dont trust the mechanic who last changed the oil/filter combo .

No one mentioned changing oil after either additive ?

Maybe the Techron is making it run better lately. I used two quarts of Techron to one tank. I saw a remarkable difference.

The oil usage from leaking valve stem seals was not even noticeable on my car because I changed oil every 2,000 miles anyway.

Someone on this forum suggested that I change oil after running a heavy dose of Techron because some of the carbon or gunk it breaks loose could end up in the oil. It sounded like a reasonable precaution.

Are you sure you're not hearing any valve ping at all when you first accelerate? The 119 engine has a pretty high compression ratio. If an injector was clogged and one cylinder was leaning out, I would think it could cause detonation.

Are you running at least 91 octane?

Yes, change the oil after the Techron treatment. I don't know about the Lucas, but the same probably applies. It's because some of that strong detergent ends up in the oil, compromising it.

What ever happened to the spark plug wires?
Regards, Eric

I just realized I did not answer this suggestion. I have had the air filter housing off 3 or 4 times. I have looked at breather hose and it looks OK and I mentioned it to my mechanic and he said it is OK .

I always run 93 Sunoco or BP . I dont know what a valve ping sounds like . Rememeber most of my tests are done in NYC and there is a lot of external noise . Is a valve ping loud?

One time I would swear I heard it backfire. Also when we were in the country checking for wires arcing it was 11 Pm and we did it on quit country roads. My wifes cousin who was helping me, used to build and race track cars (Mustangs ) and he test drove it and said it was dying, sputtering, but never mentioned valve ping.

These dam storms are stopping me from getting it on the road and burning that Lucas additive out Grr

Here is a link to a temp thread I started as someone said my temp fluctuations are abnormal and could be causing me problems

http://www.peachparts.com/shopforum/showthread.php?p=2413559#post2413559

MY new mechanic test drove it when it was warm and breaking up under load , and changed his theory about plug wires. Now he says they are not the problem .

He made me use a Lucas additive and is searching for used injectors to swap out

Well I just went down and started the car which was parked overnight with a friend looking at the exhaust. When it first started it blew a whitish grey smoke he said. I turned it right off.

I switched positions and within about 30 seconds fired her up and I saw what looked to me like whitish grey smoke also.Turned her off .

I waited about 1 minute and had him start it up again. Whitish grey smoke for the first few seconds.

What relationship does this have to engine breaking up when warm and under load ? Does it have any connection with injectors that my mechanic wants to try/swap out with used ones?

I described the possible relationship leaking valve stem seals would have to your hesitation in the post above. You can live a long time with leaking valve seals, but if the oil accumulates on the top of the piston, it could give you detonation or preignition problems that would cause the ignition to retard under a loan. I don't know for sure if that's the problem, but I believe this is what happened to me and the Techron solved the problem.

I haven't read much about fuel injectors going bad on the 119 engines. I would ask your mechanic if he did a bleed down check on them first before he started swapping out injectors. The injectors expensive ($200 each). If he gets in there and disturbs the engine wiring harness (most of the wiring harness consists of injector wires), you could end up with more problems than you have now.

I misunderstood. You are saying the coking up could cause intermittent stalling under load when warm . I have been reading so much , I am having a tough time focusing .

Would the white smoke show up 3 times in a row, and not burn off in the initial start ? Its because I am not sure if it was white or grey or a combo of the two, and I have never looked at my start up exhaust before

I also spoke to a MB dealer parts guy , who has his job for 12 years and said the injectors were not particularly problematic in the 119s. He was going to swap them out with used injectors from another car. I am not quite sure if he was borrowing them or what ,as he did not mention money to me at all.

I will tell him to be carefull ,and watch that he be especially carefull when switching injectors if that is what he wants to try next!

I am sorta putting myself in his hands , with suggestions from you guys also to check out by myself if possible , or run by him .

Before I would let anyone start swapping injectors, I would build the code reader and pull the codes. I didn't read if you changed the fuel filter. If it's clogged, it could cause the engine to lean out and you could experience similar problems under a load.

You can either spend a lot of time and money throwing parts at the car, hoping that you get lucky, or you can pay to have a good MB tech trouble shoot it for you. Many of us here prefer not to take our cars to a tech because it's kind of like admitting defeat (at least that's how I feel).

Do not let anyone do another thing to that car until they know for sure what exactly is wrong with it. A good mechanic should be able to figure it out without throwing parts at it. Anyone can do that!

Finish running that cleaner through your engine. Change the oil once it's done. Build and then use the code reader!

As cold as it is right now where you live, that "white smoke" just might be steam.
Regards, Eric

I agree. The code reader should not have been a skipped step.

I am a little confused . From what I have read the code reader that I build will pull the codes that the dealers scanner that plugs into the 39 pin connector will , at best.
I watched him use the scanner when we changed the fuel filter last week . Also my friend / dealer mechanic who I know for 15 years said it gave him no codes.

Are you saying the code reader I would build would find codes when the MB scanner would not ?

Both of these mechanics are Techs . Do you think I could do better on my own with the code reader than they can with all their equipment

Eric do you think the code reader I would build is better than the 39 pin scanner that 2 Mb mechanics have used? I have physically watched him use it and draw no codes . What will I gain by using the one I build.

PULLED CTS SENSOR
 

Someone suggested CTS sensor since it only happens when car is warm. maybe I could fool ECU into thinking car is still cold.

Here are the results:
Well well Iive and learn . First I found the CTS sensor and when I looked at the wiring I saw some wire was exposed and the black covering sorta crumbled a little more as I handled it.

So much for the condition of my upper harness ( I think ) . I proceeded to take connector off engine with engine off , temp approx 95C pre disconnecting it , restarted and drove it around a little . No difference . Engine missed at the same RPM 1400-1800 under hard acceleration. Feathered throttle produced no engine miss as usual

So then I turned it off for about 1 1/2 hours to cool down and retry. When I started it again the K6JRF view in the climate control window on position #6 said LOW instead of a temp.

But the instrument cluster showed the temp approx 65C. Also the instrument cluster temp gauge got up to over 80 C in city driving , and back down to 70C on the highway . When I first start in the morning the cluster gauge shows below 40C and at that temp it never misses .

Now we know that the car has 2 independent engine coolant temp sensors. EUREKA

I left the sensor disconnected and drove home.
The miss/bogg was still there. Nothing seemed different at all ! Actually after a half hour of highway driving , and slowing down to 40 MPH and 1700 RPM an attempt at rapid acceleration without a downshift caused the famous miss/ bogg 2 more times and one time I was going slightly downhill.

The longer the engine is running regardless of temp at the moment , the more likely the engine will bogg down.

I am going to let the car cool down entirely overnight , so that I know I am at the same starting point and drive the car tomorrow,let it run 30-60 seconds , and see if it STILL NEVER MISSES COLD, and at what temp it will start to miss when warm as usual , with the CTS sensor on the engine manifold disconnected .

I am also going to build the code reader this monday

The above quote is from post number 58. Like I said, it is a known problem of MBs of that time period and all of your techs should have known to check this as a possible source of your problem which is why I have doubted their competence all along. Now that you know that your wire harness is bad, you must address that before you go any further. That rotten harness is causing your ECU to receive confusing signals from the sensors. And leaving the CTS disconnected is not the answer either.
Regards, Eric

Just as you say in post #58 the harness is a problem in these cars. When I first called my second Mechanic ,before even meeting him , he told me over the phone my year car was notorious for that problem. He said it was related to the Green Partys policy in Germany about wiring being ecologically sensitive, and biodegradeable . So I knew in advance , that he knew about the harness.

But then he said it is OK and I believed him . The wiring on the CTS sensor is supposedy one of the the most likely areas to break down.

Only one wire was partialy exposed and the other was fine . Does that necessarily mean the entire harness is bad? I am going to do a separation of those 2 wires and then coat them with rubber paint . Where else should I check the wires. I hear the connector by the injectors is next and I also hear that the harness usually goes bad in the engine bay, where heat is the highest and moisture is a problem .

I also am sceptical because this started the day after I put that questionable gas in the car. I am also sceptical becase it only happens when the engine is warm, and only when I try to accelerate aggressively in the 600-2000 RPM area.

If I choose to drive by accelerating gently, instead of aggresively, which is how I usually drive to baby my tranny etc.,I can drive for the next ten years without the car missing a beat IMHO. But I know this is not normal and that bothers me.

I will also inspect the rest of the wires myself. But my wifes cousin looked at them. 2 MB trained mechanics looked at them , and aside from what I found yesterday everyone said they looked good.

What happens if I just replace the harness, and it is the MAF that is bad, or the injectors, or the plug wires, or the coils, like my first 15 year trained certified Benz Mechanic said. Am I not just becoming a parts changer like the mechanics that we mention in this forum ?

I appreciate all your help and I am not being argumentative, but like you I want definitive proof of a part being bad , before I go changing it.

Which code reader do you advise I make

Make Jim F's code reader but you won't be able to believe what it says until you replace the harness.

Like I said before, the areas that are the most hidden are the areas that rot the most. Under the air cleaner, look inside the hard black housing that runs along the passenger side of the engine, you'll see some more scary wire insulation rot. And that CTS wire? The further inside the sheathing you go, the worse it gets. You probably haven't seen the worst area cause it's too far in.

I was told over 4 years ago on a thread that my harness was bad. I looked, checked and found nothing. I posted that they were all wrong and the wires were good. Three years later I was at a junkyard and saw an M119 car partially disassembled and saw that area inside that housing. It was scary! I went back out into the parking lot and immediately checked mine in that area. It was scary too! Yes, I've milked that rotten harness along now for over 4 years but that doesn't mean you need to. If it's bad, replace it. Even if it's not causing problems now, why wait for it. It won't be pretty when it get's you and it will be at the worst possible time too. I'm on borrowed time with mine. And it does have days where it causes me maddening fits. But at least now I know what's causing it.

It is true we do not replace anything unless we know for sure it needs to be replaced, but in this case, we now know it does so we should.:):D;)

Even if doesn't cure the issue, it wasn't wasted time or money cause it was something that needed to be done anyway.
Regards, Eric

I will probably replace it and do all the proper maintenance becuase I love my car. But I need to know what is causing this particular problem and fix that first. I want to eliminate that flat spot and being a hard headed Greek that I am I want to do that first.

Then I plan to change motor and tranny mounts , flush tranny, replace thermostat , gas up the freon, maybe plug wires or maybe later, and at least clean MAF.

But first I what to find out what is causing this hesitation when warm only.

My wifes cousin swears by a guy who does a cleaning process on injectors and who said the throttle body could need it also . may try that plus cleaning the MAF first .

Now I am taking the car for a ride with the CTS sensor disconnected .I will post my results .

Thanks again

Again I appreciate your thoughts , but I would still prefer to cure the problem , which in my case is very slight and can be avoided by just not stomping on the gas till after 1800 RPM .

In reality if I was not an obsessive perfectionist , I could drive this car the way it is for prolly another 50K miles. Two friends of mine have already said leave it alone and drive gently till it gets either better or worse.
One of them is a very close friend of mine , my skiing buddy , and a Doctor. He thinks I am nuts obsessing about it ,and he is a Psychiatrist . Leave it alone and just drive it he says .

Not good enough for me .
I must solve this problem , but not at a $1500 or $2000 cost on a gamble .

My cousin recommended a guy named Chris who has equipment to clean out fuel injectors .

I went to see Chris.He works on all types of cars. His shop does oil changes and various other things. He was helpfull and we took the air filter housing off and he said the Fuel throttle assembly was spotless. He said it looked like it had been cleaned very recently.

I told him Joe my BenzDealer mechanic had it for a few days and changed plugs etc. and maybe had cleaned it

He said it looked like it was clean, but then sprayed some CRC Mass Air flow cleaner in it while it was running.

We looked at all the wires , vacuum lines etc., and he thought his $70 process would be a waste of money so he did not even do it. He thought MAF would cause a rough idle and not the symptoms I described , but admitted he was no Benz mechanic and recommended someone else for me to see IF I wanted to.

While we had the hood open I saw that the sensor beneath the coolant tank was not plugged in or in its bracket . Prolly from the time I had my coolant changed or one of the mechanics who has been looking in there disconnected it , to check it and forgot to reconnect it , and put it back in its proper place.

After we closed it up I took it for a ride , same thing, miss on heavy acceleration with engine over 70C .

Chris said when it is running cold , it compensates for the lean mixture by giving it more fuel, thats why it never misses/boggs when cold .

He liked the FUEL REGULATOR not working properly theory someone postulated in another forum a lot.

Willy the guy I am using now (Let me give him a name so you do not confused with the first guy (Joe dealer mechanic ) who up until today, had said it was prolly injectors ,and today changed his mind to coils, said that tomorrow he might be able to swap out a coil. It migh be injectors was his first thought. Thats after changing caps and rotors which we did already .

Chris said in his experience electrical things usually work or they dont . He thought coils was unlikely to produce my symptoms. Does anyone agree or disagree with the coils theory applying to my symptoms

It drives so dam well when past 2000 RPM etc and I had it going at 60-75 MPH today off and on for an hour. The only thing is at those speeds engine really cools down to approx 70 C so engine temp is lower,therefore the problem is eliminated ? Only runs bad when warm and pushed under load.

I dont think I know enough about sophisticated cars from working on them in my youth mostly. But the way it drives after it gets past 2000RPM is wonderful. It feels as good as when I got it with 29 K miles on it 15 years ago.

Aside from that one little glitch it performs flawlessly. Its peppy on the highway ,starts up easily even when sitting out for days in the freezing cold idles like a kitten and accelerates wonderfully by downshifting or just applying more gas , after 2000 RPM.

Chris looked at the harness and said it looked good . I find it hard to believe it is top harness.

Hopefully I will get Willy to swap out a coil tomorrow to disprove that theory.

Maybe I will order the Pressure injector and have someone else put it in since Willy doe not think its the problem . Is that an easy part to change ?

Any more creative ideas, that can tie together my symptoms, and lack of symptoms ,to eliminate things, and then be left with the only sensible deduction .

What do you think of, keep on running it hard and letting the gas run down to almost empty, like 1/8 tank and then refill with additive?

Well with luck Willy will swap out coils tomorrow and rule them either out or in , and I will either know, or the process will go on.