92 misfiring problem

[meo 325is]

My 1992 325is has been acting-up for the last year or so. Its seems that it is running on 4 or 5 cylinders below 3,000 rpm and fine above and sometimes it works like a charm!!! I've changed the coils twice (used) and same problems. It really feels that the fire from the coils are jumping to the chassis ground. Anyone has an idea?

[blkongry]

it sounds like the same problem some other guys on here are having, and it does sound like a sparking issue. On top of making sure your coil packs are good (by checking resistance on them), check all the contacts, too. A poor contact can definitely result in poor spark.

[meo 325is]

The wiring seems to be fine. I'm an avionic technician so I'm pretty good with wiring but this one is bugging me big time.

[blkongry]

Then if you've gone through the wiring, checked the plugs, made sure everything is clean, connected, and sound, then it goes back to a control problem with the DME. Do you have access to a second DME where you can check performance? Also, there have been odd problems with engine control with poor grounds to the DME... I don't know where the ground is, but you may want to check just to be sure.

[meo 325is]

Do you know where is the DME? Is it the same as the ECU which is located under the R/H wiper? The plugs have been changed!!

[blkongry]

Yes, it's the same as the ECU, and its behind the glove compartment box (accessed from under the hood) under the rigth-hand wiper. I don't know where the ground is, but you can pull out your DME and check for sign of corrosion or contamination... that would be a good indicator of something wrong with it.

Now if you've got good plugs, good coil packs, clean connections, then you are tracking the problem back... and it looks like the tracking is taking you to the control system.

[meo 325is]

Thanks,now what do you mean by control system?

[blkongry]

I just mean you're tracking it back from the end effectors (the spark plugs) all the way up the system to what controls that spark delivery (the ECU/DME). Your problem has to be somewhere in between.

[meo 325is]

Thanks very much.I removed the ECU and it looks fine(no sign of moisture). Do you have an idea how to isolate the coils so they wont spark to the head. If you have other ideas, feel free to tell me. Thanks again

[josev]

Originally posted by meo 325is
Thanks very much.I removed the ECU and it looks fine(no sign of moisture). Do you have an idea how to isolate the coils so they wont spark to the head. If you have other ideas, feel free to tell me. Thanks again

wait until it is realy dark out open hood turn the car on and look at the coils to see if you see any arc across them also water or moister will make the arc

[geladen]

This may sound dumb, but make sure that you don't have any oil going down into the spark plug holes. If you have a leaky valve cover gasket, especially the rings arund that spark plug holes and you get any oil down in there around the plugs, this will act as a bridge for the spark to ground and cause a missfire.

[meo 325is]

There is a very small amount of oil, I will clean that out. Thanks

[mdistel]

If you haven't replaced your valve cover gasket it may be a good time. It can really leak a lot of oil into the plugs which causes all sorts of driveability problems.

Mark

[meo 325is]

Thanks Mark. This should not be a costly nor a very hard task to accomplish. Thanks again

[meo 325is]

Hey guys I found my problem. It was #5 cylinder plug that was loose!!!
Thanks for all your help. Meo