Car is stumbling and running VERY rough.
 

My car is running very rough. It has the feel of a spark plug wire that came loose from the plug. If I step on the pedal it stumbles before it runs, but upon deceleration it continues to idle poorly. I have removed my throttle housing and checked every vaccum hose and all are ok. IACV was cleaned with carb cleaner, and tested. I unplugged it and the idle was still rough, but it began to idle high. OVP was checked and swapped out with a spare one I had, made no difference. I took off the cap and cleaned that plus the rotor, distributor cap is new. I checked the spark plug wires, all are new. My spark plugs are new, but I pulled them all anyways and swapped them with a different set. Made no difference so I put the other ones back in. Only thing I can associate with the running rough is that I put some engine oil stop leak and seal in the crankcase today, but I doubt that would cause my car to run rough. Anyone know what else I should be looking at as the culprit?

Dirty injectors would be the 1st place I would head. Lucas additive sure helped mine.

start doing your homework on Bosch KE jetronic fuel injection! It sounds like a fuel problem.Start with checking the duty cycle their are many posts on it.

Just pulled all injectors and guides and cleaned them all and replaced o-rings. Method for cleaning injectors was nothing fancy: carb cleaner, the small red straw fit perfectly into the injector, and spayed. The spray that shot out of the front was a nice even spray.....but I still have the problem :-(

bump

Tried almost evrything and still no good!
 

My car is still running rough and has poor acceleration/ or stumbles when I take off from a stop. I have replaced the distributor cap twice within 2 months, spark plugs and wires twice within 2 months, changed the O2 sensor twice, it is a new Bosch O2 sensor, IACV hoses are new, replaced the IACV twice, cold start valve twice, ignition coil twice, ignition control module twice, EGR valve, I even swapped out my KE-Jetronic distributor! I am not getting any codes. As far as I know, all fuel and ignition components are in good standing. I turned the key to the on postion then off and went and cracked open the main fuel line and there is definitely pressure there from the pumps. All spark plugs get spark, I rechecked them at least 10 times. Last night I checked all the vacuum hoses unde the hood and all were fine. Anyone got any other suggestions?

Bad gas or clogged cat?

Consider a compression test. Also, did the plugs all look identical and tan?

plugs are all new and not showing any abnormal deposits. gas has been refueled several times with different stations. maybe clogged cat? I changed the rotor again yesterday with a used one and car still stumbled, however it cleared up nearly all day yesterday then started back up again today.

How is your EHA? Is it original or leaking? I replaced it on two W124s with similar symptoms and got good results.

Your cat is unlikely clogged. If it was you would be failing smog left and right.

Swap EHA.

On a side note, don't put any of that stop leak junk in the crankcase. Just gotta fix the bad seal wherever it is. No way around it.

EHA was replaced before, it is not original. I have 2 to 3 parts each of igntion/tune up/fuel related components and no matter which I switch around the same issue is still present. I went to my muffler guy and he too said that the cat is fine and that I have a misfire under load at low rpm, he though it was maybe a vacuum leak. I have a vacuum tester and was checking each line for a leak, the only one I found was to a red/light blue striped line on the driver side behind the firewall right above the brake booster. I traced the line down into the front passenger wheel well behind the plastic panel. I removed the panel and the line terminates into a black plastic bouy type ball that doesn't appear to connect to anything else.Its attached to the wheel well and has nothing else connected to it other than the vac line coming from it. I also put another brand new Bosch distributor cap on today as well (because I ended up checking and rechecking my ignition components I ended up breaking the carbon top in the center) This is got to be the most frustrating thing ever. Even the electrical fire I had I was able to replace the wire harness in 8 hours. But this I have been dealing with for a couple weeks now.

i had this problem once and there was some stupidity on my part. firing order was not correct..so i was operating on 4 cylinders instead of 6.

I'm pretty sure the firing order is correct, my car isn't running that rough. I do remember doing this once and starting the car and the car was EXTREMELY loud and ROUGH. I turned the car off immediately (not because I was afraid of engine damage, but because it scared the $#!*$ out of me. My issue is more of an actual misfire like there is a loose plug. Well I have another appointment with my mechanic on friday. Hopefully I can get this resolved. Unfortunately I only have the one car so I hope that I am not causing more damage to anything. :eek:

x2 on EHA.

Changed the eha already, no change

With a brand new unit?

Yes, maybe a year ago.

You should check your duty cycle and report what it says. Also, can you give a vacuum reading? One at idle, another at 1500rpms or so.

Further more, don't think your injectors are good just because they are not clogged. They can be lettng TOO MUCH fuel at idle causing the misfires, until it can burn it out.

Swapping parts is the most frustrating way to try and fix a car.

When your tank is full, does it still run like hell? I'm having the same problem when my tank is a little below 1/2 on my 95 E320. Once my tank gets to that point I'm going to take off my gas cap & put it back on to see if it hopefully clears up. If it does, it could be a clogged venting system.

Should start to act up pretty soon here... I'm currently a little above 1/2.

Sticking valve stems!!!
 

I shoulda known! Everything fuel/ignition related is brand new. Took it to my mechanic and he said the valve stems were sticking. That would explain why th symptoms went away sometimes. On my way to walmart right now to get some seafoam and fuel additives. This happened after I added some ring seal stuff to the crankcase. Hopefully the aseafoam and fuel additives clear it up. I'm going to go fuel up and take it for a long hard drive too

Please keep us posted on the results. How did the mechanic spot the problem?

What oil are you using?

Ismalley, valve stems sticking ... that's a creative explanation. Forget about oil additives. That's what caused the problem initially. A high quality oil will keep the engine internal parts clean. Recommend changing the oil and switching to Mobil 1 15W50.

cheap gas
 

Look at the brand of fuel you and previous owners are using. Its not just about good oil with sticking valves,cheap gas will cause problems with deposits. Using premium fuel is not good enough it must be good quality fuel. Shell and Chevron are good at preventing deposits cheap sams club gas causes deposits. I have experimented with this on my cars and it really does make a difference.

How much seafoam are you adding to a tank?

How often?

EDIT: while I picked up a can of seafoam, I noticed there was a seaform treatment for auto transmissions.
Anyone have any experience with it?

so I ran a bottle of techron and used lucas fuel cleaner and the problem is still there. I drove half way to Arizona from California using chevron 80 mph most of the way. I use Pennzoil 20-50, was using gtx 20-50. I took the valve cover off yesterday and tapped on the springs. unfortunately it was night so I couldn't see.

Can you get good compression results when tested despite this problem?

I ask because I had a compression issue on #2 and #4 on mine around May 2012. Had the top end rebuilt with new gasket, new valves, guides, seals, and new timing chain. Compression went back to 185 psi all around.

Was a shot in the dark since there was a risk the compression problem was in the block too (rings/etc).

This poor compression caused similar issues (rough idling and stumbling) and eventually led to stalling.

Have not checked the compression. I don't have a machine. It actually ran fine today and only stumbled a few times. Just as a precautionary measure I had the battery, alternator, and VR/diode tested yesterday and everything was fine. One thing that I would like to add is that I noticed that when it stumbles some the instrument cluster light dims a bit, but just on a rough stumble. Also, when the car stumbles or idles rough there is no change in my actual RPM tach, it remains at a solid 500-750 rpm. Also, my check engine light is on now which gives me code 11, air injection system. I don't know what that means, but I have been getting a code 11 on and off for several years now. Thank you all for your replies in helping me troubleshoot this problem, I really appreciate it. It just sucks that I just got a new/used transmission put in in Dec. and pretty much every starting/charging/ignition/emissions component is new and I'm having this problem. Is it possible the additive I put in messed something up? I'm almost positive this problem was not present until I added Rislone Compression Repair with Ring Seal.

Those snake oils do nothing at all. Switch to a good diesel oil to help clean that crap out whatever it is. Delo 400 15-40 you can get it at Walmart cheap.

You need to address that check engine code. There's a reason why it's coming on.

I just changed my oil the other day. I may have too switch to something with more detergents in it, but I'm trying to avoid getting a leak since the engine has over 340k on it. And yes, that damn CEL code 11 is like a ghost, sometimes it will be gone for months then it will come on and I'll reset it and it goes away again for a long while. I don't even know what is meant by air injection system. I replaced all the components related to the air pump and I know the pump is working. But like I said, that code will clear up and be gone for months. It's strange. I'm certain it has nothing to do with my current situation, though I can't be 100% this time because the code won't stay away now.

Additional Info
 

Not sure what this means, but I just realized that if I am sitting in my car with the ****er in either position( P, R, N, D, 2, 3) the roughness in the idle that I feel, magnifies x 10 if I turn the steering wheel in either direction. Even if the car is idling smooth and I am stopped, when I turn the wheel the car shakes hard while turning. I lifted the hood and there is fluid, but upon listening to the engine I did notice that I can definitely here a hissing sound. Is there a vacuum line that goes to the power steering? Would this cause rough idling?

A vacuum leak could cause that I believe. Our 420SEL had a number of vacuum leaks that cause some stumbling on acceleration. Are you sure the hissing sound if coming from power steering system?

Side question, why 20w50 oil? I run 0w40 in my 190E. However its only got <120k miles on the motor.

Dude, quit guessing and check your vacuum with a mity vac. Then check your duty cycle.

Vacuum should be more than 10hg, ideal is 12-15.
If you have any voltage tester you can just check to see if you get 6ish volts at you x11 port.

These engines are very crude, and uncomplicated

I used a vacuum tester and I got between 15hg and 18hg at the intake and also I checked all vacuum hose with a vacuum tester. Everything was good and held vacuum except for 2 things: 1 was a red hose that terminated into the passenger wheel well into this black bouy-type ball and the other was the line going to the vacuum modulator of the transmission which had an extremely slow leak, but also no transmission fluid was coming through the line so the integrity of the diaphragm is still good. I also did the duty-cycle using that landiss_ke jetronic write up. The write up states I should be getting volts between 4.6 and 6.1 which I am getting. It fluctuates and jumps around, but it jumps around within that number ranger as indicated and mine is a California version.


I am 90% sure it is coming from the power steering if that has any type of vacuum to it, if not then I guess it could be normal intake manifold air, but its definitely hissing. Sprayed carb cleaner around the entire intake manifold gasket, fuel injectors, and IACV while the air cleaner housing was off and got no change/surge/drop in idle. Sprayed some on the throttle plate and the idle dropped as if to stall then shot back up and evened out. Is there a hose that goes anywhere to the power steering that carries vacuum? If so, please advise where it is located and I will check it out. As for the reason I use 20w-50 oil, the owner's manual that came with my MB states that 20w-50/20w-40 is acceptable if the ambient outside temp is constantly +32°F and above +86°F, where I live its usually in the mid 70's to the mid 80's year round....except the summers which reach 110°+. But yes, please advise of he PS vacuum infomation. I tried looking it up, but only got issues pertaining to PS fluid leaks. Thanks

As far as I know there is no vacuum related to the operations of the power steering system.

A pump, two lines and the steering gear box.

When you turn the wheel it briefly lowers the rpm at idle...if its already stumbling, its going to make it stumble more, so that is typical. Nothing wrong with the steering.

15-40 shouldn't make anything leak more than 20-50. How much are you topping up each week/month currently with 20-50? regardless of being burnt, or leaking out.

I put maybe about 1700 miles a month and I only add a quart in between my oil changes which is usually every 4k - 5k miles. Everything seems sealed up pretty tight.

Did you get 18hg at idle?

it was between 15hg & 18hg. why, is 18 bad?

No, but at 18hg you have the tightest vacuum system I have ever seen. The very best I ever got my car was 15hg after replacing every rubber bit under ther hood.

What are you idling at? 650?

Perhaps you could post a video, might be helpful too.

Also, what kind of mileage are you getting?

Idle is at 500 in D and about 750 in P or N

I'm working on getting the video together just been really busy.

No video, lost phone in Feb and had to get a cheap one with mediocre cam quality. Problem is still there, rough idle whether or not engine is cold. Opened up valve cover, removed rocker arms and sprayed penetrating oil on the valves and gave them a nice tap. Did nothing at all. I'm now wondering if that is even the problem. Anymore suggestions? Could it be something I am totall missing that is so easy to fix?

I dunno if this applies to your car but have you replaced the insulator behind the distributor cap? This is often overlooked, as noted in this Star article:
http://www.w124performance.com/docs/mb/M119/ignition_misfiring_STAR.pdf

I am still having the rough idle issue on my car, but I notice that it gets somewhat better when the car warms up....but not just warms up, but after the car has been driving around a bit in stop and go traffic in 100 degree weather and the temp gets hot enough for the aux fans to come on. Does that indicate something?

rough idle resolved
 

Issue was a stuck intake valve. removed all spark plugs and all fuel injectors and used a 20cc syrings filled with lucas fuel conditioner and sea foam and blasted it into the fuel injector ports to clean up and lubricate the valves

Nice work! Bet you're glad you found the issue.