Car is stumbling and running VERY rough. - PeachParts Mercedes-Benz Forum

lsmalley · #1 03-02-2014, 04:12 AM

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?

TnBob · #2 03-02-2014, 02:42 PM

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

johnflight1 · #3 03-03-2014, 12:10 AM

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.

lsmalley · #4 03-03-2014, 12:41 AM

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 :-(

lsmalley · #5 03-14-2014, 12:58 AM

bump

lsmalley · #6 03-16-2014, 12:49 PM

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?

mpolli · #7 03-16-2014, 07:17 PM

Bad gas or clogged cat?

Hirnbeiss · #8 03-17-2014, 07:54 AM

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

lsmalley · #9 03-18-2014, 01:06 AM

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.

124126140 · #10 03-18-2014, 04:59 PM

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

ps2cho · #11 03-18-2014, 05:45 PM

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.

lsmalley · #12 03-19-2014, 03:36 AM

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.

lee polowczuk · #13 03-19-2014, 08:35 AM

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.

lsmalley · #14 03-19-2014, 11:18 PM

Quote:

Originally Posted by lee polowczuk

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.

MBeige · #15 03-19-2014, 11:38 PM

x2 on EHA.