1995 E420 Rough Idle - M119 - PeachParts Mercedes-Benz Forum

dproudfo · #1 04-16-2009, 02:14 PM

Transmission mount and motor mounts were replaced last August. (Sachs/Boge) I'm assuming that if either of the mounts failed that there would be noticeable fluid leaking?

Clamp was tightened after install of the MAS gasket.

dproudfo · #2 04-19-2009, 08:12 PM

Are there additional tests that I can do with my injectors? Do places like witchhunter.com work well?

Keep me posted.

deanyel · #3 04-19-2009, 08:48 PM

Quote:

Originally Posted by dproudfo

I'm assuming that if either of the mounts failed that there would be noticeable fluid leaking?

Yes, fairly quickly I believe. Depending on where you were at the time you might not get much on your garage floor.

For injector cleaning I've good experience with http://www.cruzinperformance.com/

dproudfo · #4 04-22-2009, 06:05 PM

One note I'd like to get a little feedback on:

For testing out the plug wires, I sprayed down each one with water/Windex along the shaft to the plug ends and had some really noticeable arching between the spark plug end and the cylinder wall. I thought all of that should be insulated preventing this. Am I correct in this assumption and in diagnosing a potential problem with the plug wires? (I used dielectric grease for everything as well)

Keep me posted...

dproudfo · #5 06-18-2009, 06:15 PM

I wanted to post an update to see if this symptom may or may not shed any additional light on the miss at idle that I'm having:

The car sat for the last 3 days and upon starting it for the first time again, the car began missing A LOT (It was clearly not firing on all 8 cylinders) It ran poorly for about 30 or so seconds and then stabilized to its usual idle. This incident points me in the direction fuel delivery, possibly a leaking injector. Anyone else have any insights on the issue?

dproudfo · #6 08-17-2009, 02:27 AM

Yet another update on the rough idle problem...I sent my injectors out to Cruzin Performance to be cleaned and bench-tested. In addition, while the injectors were out, I pulled the throttle body and detailed the underside of it to ensure that 'build up' wasn't a factor in my idle. When the injectors were re-installed, the engine seemed to hunt/re-learn fuel/air mixture (a different post) but the end result was pretty much the same as it was before so I can now officially check injectors and dirty throttle plate off the list. Anyone have any ideas based on the previous posts on where I can go from here?

Thanks again!

emerydc8 · #7 08-17-2009, 07:01 AM

This is a shot in the dark, but did you try to recalibrate the fuel adaption when you got it back together? The following post was from Arthur Dalton in post Cause of high fuel consumption E420

Quote:

You can reset adaptation back to Mean Base Line by re-setting/re-activating the ECU memory . After you have cleared all existing codes [Single flash verification ], you then hold button for 6-8 secs. after the single flash. [wait 2 secs after single flash].. Turn off key for 2 secs, On for 10 and then start.

This is NOT a code clear, it is ECU memory reset. That gets your ECU back to Normal . From there the unit will adapt to the new parts and sensors, but rather then coming back from high adaptation extremes, it will come up/down, +/- as required from a Normal Base value.

The ECU can/will readapt from the old memory by itself with drive cycles [ relearn process] , but if the trims were way out , you can still get codes coming back while the process takes place..so, it is easier to just clear/reset the memory after you have changed parts and have cleared the diagnostic codes ..you are then assured of starting with an ECU that has a Mean Base Line setting value..[ ie..a Normal setting]..which should be closer to proper adaptations with the new remedy parts.
Just a short-cut........

Also, as SB mentions..FP regulator leaking diapragm will supply the engine with unmetered raw gas..not only will the engine suck raw, un-metered gas into the intake from engine vac , but the Fuel Pressure will go higher than spec and compound that problem...that would be a first check..
the same can be a vac leak..a vac leak of unmetered air is read by 02 as a lean condition , so th ECU tries to enrichen this false reading, resulting in wrong A/F mix..

Both reg and vac leaks will force trim levels +/- that it may not be able to handle [ beyond limit].........and result in crap MPG/Running condition.
If one does find a leaking/bad FP reg, it is also a good idea to change the oil.

dproudfo · #8 08-25-2009, 12:21 AM

Tried the reset...no result. The car seems to run rougher in the morning if its sitting out overnight which leads me to believe that it's ignition related. (also runs rougher in the rain) I can't think of where to look at this stage. New caps, rotors plugs and plug wires within the past year. The only things left are the ignition coils and I'm not suspect of those because of the fact that my major problem is at idle which isn't very hard on the coils. ANY additional insights would be great!! Thanks again!