OK,,, I give up
 

Taking the 320 in to my indy tomorrow to try to get the idle surge figured out. Through the help of the forum, I have tried everything imaginable, but it is actually getting worse, so it's time to bite the bullet. Will let you know what comes of this diagnosis.

Okay, Pete. Good luck! Just don't get upset . . .







I'm sorry. I know I shouldn't have said that. I just couldn't help myself.

After owning these Benzes since 1993,,,, I don't get upset any more.:D

Don't feel bad...my idle surge was the first thing I ever posted here (2001) and I never solved it either. My indie discovered the bad vacuum hose just last year.

If it is a bad hose, I'm going to have it gold plated and hang it on my wall.

Check the EGR pipes for blockage.

http://www.continentalimports.com/ser_ic20134.html

Did the new EGR about 2 months ago. Surging started shortly after that and am wondering if there might be a tie in there.

I remember one of Johnhef's friends trying to diagnose a problem like this. He was a very seasoned MB Master Technician and an excellent diagnostician. He said problems like this were a real bear to diagnose correctly.

Having said that, I guess anybody would have a tough time doing it. This is probably why mechanics are often accused of "throwing parts" at problems. That doesn't make it any easier when you're the one BUYING the parts, though.

I have seen EGR SOV valves not closing completely ..this will effect egr closing.
The test is to put a BB in the vac line between the egr element port and the SOV and run the car for a few days.
No surge = you have narrowed down the cause.

I also do a manual egr test and part of that test is to make sure the egr SNAPS shut.

As the problem came with EGR change, it also possible that you have a simple vac leak anywhere in between the egr and the intake at the engine ..this could be as simple as the mount bolts/gasket at the intake side or a loose fitting of the cross tube from the valve..

The idle surge problem with my C280 was caused by the purge valve/regeneration valve. Every time the code was tripped for it, I would clean it out with some WD40, as per Arthur's method. I finally got tired of doing that all the time and I just bought a new valve Instant cure. Your E320 has the same M104 engine so it might be worth looking at. To test the purge valve just hold it in your hand while the car is running. You should feel it pulsing, like a heartbeat. If it isn't pulsing, it ain't working. It takes all of 3 minutes to replace, no tools required.

I was just out checking on the car and they told me "it's fixed". Said I had 2 bad vaccum hoses under the car some where. I hope to get more specifics when I pick the car up. Great news though.

I want to see a photo of these two bad vacuum hoses gold plated and mounted on your wall. :D

Son of a gun Paul,,,, they threw them away already.:D

Oh for the love of God.... :wacky:

Crank vent tubes, is what they said they replaced. Under the intake I see 2 new rubber like tubes that are about 1 inch in diameter. Whatever, it sure cured the problem, I think I can stand a dime on its edge on the hood with the engine idleing.:D

Do you still have a dime left after the repair? :D

Yep,,, diagnostic, parts and install were $184.
This is one time I should have seen my indy first, but hell,,, you never know.

Someone please tell me where this is located in my 94 C280. New MAF an EA...still surging.

Under the hood, on the driver's side, front of the fender well. Very close to the ABS pump. One electrical connection, plus one vacuum hose leading into the back and one vacuum hose leading out the front. The letters "MOT" are on the top of the unit. Here is what it looks like:

http://catalog.peachparts.com/ShopByVehicle.epc?q=1994-MERCEDES--BENZ-C--80&yearid=1994%40%401994&makeid=63%40%40MERCEDES+BENZ%40%40X&modelid=6333%3AMBC|1556%3AED|10000015%4 0%40C280&mode=SS&yearid=1994%40%401994&makeid=63%40%40MERCEDES+BENZ%40%40X&modelid=6333%3AMBC|1556%3 AED|10000015%40%40C280

hai pete,
dont worry it will be minus now but it will be lesson for you,:o
for other works.
------------------------------------

steven

view for free communication

How did you "clean it out"? I assume you mean that you used qtip type cleaners with wd40 and just cleaned out the passages as best a you could? I do not feel a "pulsing" of any kind.

If running WD40 thru the valve and lines does not clean it up , I have a good technique for stubborn ones with stuck pintles

The main part that hangs up is the pintle pin from the solinoid ...so, you take the valve off the car and squirt BP Blaster or carb cleaner into the valve and leave it over-night UPSIDE DOWN... that gets into the pintle pin and frees it up. The trick is the next day, you hook 12V battery power to one terminal and touch the other very rapidly ON/OFF..that exercises the pintle pin and frees it up.. some tapping on the side helps.....you will know when it is free b/c you wll hear/feel it clicking.
You then blow air thru the vavle ports in the direction of the arrow.

When you can feel it pulse and you can blow thru it only in the direction of the arrow, you are done and it can be installed on the car w/arrow facing engine flow.
Then idle until up to temp and feel it in your hand , ..you should feel the pulses [ 5-20Htz].
You may also want to take an Om reading across the sol. terminals before cleaning to be sure the coil is good.,, you are looking for 40-50 Ohms.....if no , don't bother..

What is the best (safest) way to do this?

<<What is the best (safest) way to do this? >>

Huh ??

I just gave you step by step instructions on how to do it..

I was talking about the bolded part only -- how to hook it up straight to 12 volt. I appreciate the step by step mucho.

You say that air passage should be free only one way -- do you recall which way. My pintle is evidently stuck as airflow won't pass either way -- I have is soaking now.

Question -- what should I see as a correct result. Air passage closed both ways, one way, which way, etc? You alluded to this...but what specifics?[/QUOTE]


I alluded ????

It is a valve ..it can not flow until it is ON...it is a Directional valve..so it flows in the DIRECTION of the ARROW when it is ON...the signalis pulsed so as to meter the flow. [@ 5-20 htz, depending on ECU mapping]

Thats the specifics.

I alluded ????

It is a valve ..it can not flow until it is ON...it is a Directional valve..so it flows in the DIRECTION of the ARROW when it is ON...the signalis pulsed so as to meter the flow. [@ 5-20 htz, depending on ECU mapping]

Thats the specifics.[/QUOTE]

I clarified my post, Arthur, I guess as you were replying to it. I don't have the knowledge you do so I'm learning as we go. Now, to hook it up to 12v -- just use jump wires direct to car battery or what?

Update:

I'm standing at my workbench looking at this thing -- had been soaking with wd40 -- and about 12" away is a square 9v battery I had taken out of a smoke detector. I'm like, what the heck, let's see if it activates this valve.

Sure enough -- click, click, click. Click -- air goes through valve no problem. Seems loose and opening/closing properly.

Put it on the car...plug it in...nothing. Maybe it is working...but no pulsing/clicking anything.

Any 12v DC source...hook one side to one terminal and every time you touch the other terminal to complete the circuit, the valve should open/close..
If you soak the vave in some cleaner and do the 12v intermittant hook up, that should exercize the valve ..and you will hear it and you will feel it pulsing with each sig input.

That is what my post said to do.

.but it also said to confirm the coil of the valve is good by OHM reading it ..I even gave you the OHM SPECIFICS...cuz if the coil winding is an OPEN circuit, you can clean the valve til the cows come home without it working...so , I included that as a precautionary FIRST step.

Sounds specific to me. If it is not clear to you , then maybe just go buy a new one,.

Ok, now I'll check the ohms.

Ohms are fine.

Left the car running. Car had been running smooth as silk. Went back out there and the idle is surging. Regen valve is clicking like a drum roll...so, that evidently is not the problem.

Now, on, I guess to track down vacuum leak, or actuator or air flow meter.

Seems like it runs very smooth until fully heated up then surges.

<<Regen valve is clicking like a drum roll...so, that evidently is not the problem.
>>

You have only determined that the solinoid pintle is working..you have not determined if the flow is correct.
Take the vac hose going to the canister off when the vavle is pulsing and put you finger on the port of the valve..does it have pulsing suction??

If yes, then unplug the connector..does the valve shut OFF ?
If NO to either , it is full of crap and needs to be cleaned.
That is why my early post said to check flow.

Ok, I will do this. But...flow is good and clear when I connect it to the battery when I had it out of the car.

<<But...flow is good and clear when I connect it to the battery when I had it out of the car.
__________________
>>

I am not concerned with it being clear..I am concerned if it CLOSES...cuz if it DOES NOT , then it will fit your condition...get it ?????????????????????

Dirt can hold it open and you then have an interior VAV LEAK.....and a vac leak will cause your condition...

Arthur, I really appreciate your help. Have a little patience, I do not know these cars like the back of my hand like you do.

Ok, let me make sure I'm understanding what you are suggesting.

1. When the valve DOES start it's pulsing open and closed, take the vac hose off (the one on the "from" end of the directional arrow -- toward the front of the car, the smaller of the two valve inlets). See if I actually have a pulsing (on/off) vacuum going INTO the valve. I should have the pulsing vacuum.
2. If it does pulse, then take power away which SHOULD make the vacuum stop, correct (since no power = closed valve)? If it does stop, then the valve is working correctly. If it doesn't then something is keeping the valve somewhat open even though the electronics are saying that it should be closed.

Am I understanding your directions? In #1 -- am I looking at the correct side of the valve to check the vacuum? In #2, am I understanding your conclusion?

Thanks.

Correct.

You do not want a valve that does not close when there is no power to it...if that was what they wanted , they would not have a valve there to begin with. They would have just run a vac line to the canister.

Sorry for being short with you ,but your responces are with a.. "Yeah, BUT...." and you want Specifics...like I was NOT specific ????

I was very specific.
The reason they PULSE the vac from the canister is b/c if the engine just got a big gulp of air from the canister from a wide open purge, it would upset the A/F mixture of the engine, just like a VACUUM LEAK..so , they meter it in small pulses/doses ..that is what the frequency of the pulses are for...and they vary according to the load conditions of the ECU criteria and feedback of the mapping.
The pulses are what you feel in the valve, but just cuz you feel the sol. pulsing the actuating pintle pin DOES NOT mean the valve SEAT is shutting OFF vac when it is not getting a signal...that's all I was trying to tell you and I thought I made that clear.
Ever turn a faucet OFF , but water still leaks out...same deal, except in this case , it can effect the A/F mix to the engine just like you had a vac leak...which you may have.
I just wanted to let you know you had not diagnosed the Purge as OK correctly just cuz you could feel it pulse ..that is only part of the test for purge [ as my very first post states] You must then check flow OPEN/CLOSED. Regardless of the pulsing ....it can be pulsing all day long and not be doing what it is designed to do.[ control/meter vac flow on/off using a predetermined frequency/Htz signal]
The 3 sections to purge system are ECU demand signal to solinoid coil of purge, [ OK/OHMED] actuation of pin by solinoid, [OK/ Feel] and valve seat open/closing for vac flow when pin actuates. [ Not tested] That's it.............you have verified the first two, and now if you verify the flow test, you have eliminated or confirmed the Purge as the cause of your condition and if then verified, I suggest you look elsewhere.

Ok. That valve is evidently working as it should.

When pulsing, I took the hose off and I do get a pulsing vacuum, off/on. With power disconnected I get NO vacuum whatsoever.

The other suggested issues are a vacuum leak somewhere, mass air flow meter (new one put in 4 months ago), and throttle actuator (replaced 4 months ago with a salvage part, same #, from a 96 model. It was cleaned very well inside and wiring looked fine.

This started after head gasket r/r so I'm leaning vacuum leak somewhere before replacing those parts again. The large tubes to intake and intake gasket were also mentioned as possible culprits in the vacuum leak scenario.

Thanks for the help and expertise. If you have a suggestion on isolating the vacuum leak that would certainly be welcomed.

My first check for your condition would have been the FP regulator daiphragm port for fuel leakage into intake,

Checked it cold and hot. Pulled vac tube while running. Detected no fuel at all, solid vacuum, though didn't notice it running any different with vac tube on or off.

I'm going to reset my computer, run it, and have codes pulled.