Hi All, Just thought I would reach out to the community and see if anyone may have some ideas for me on an issue I have been having lately. Over the last few months I have noticed my car (a 95 M3) is misfiring. However it is only doing it during warm up... Initially when I turn the car on, it runs fine, but then after about 10 minutes it misfires a few times (not 100% sure its a misfire, but the check engine light comes on, then goes off a second or so later. Plus the car will sometimes loose power briefly). Now here is the interesting part. It will only do this a couple times and then stops and doesn't happen again until the next day. I am sort of assuming it has to do with engine temperature... Potential culprits I have come up with are - bad plugs, ignition coils, wires? Any thoughts would be much appreciated!
This is an odd one. It could be spark plugs or the crank position sensor going bad. Both these problems happened to my car and caused misfiring.
This happens alot. The coils on this cars fail. If you have a code reader, findout which cylinder has the misfire. Then move the coils around and see where the misfire is after that. But make sure to make the coils when you move them. Thats the easy way to find the bad one.
I agree ..with SuperBimmer. The coils and plugs would be my first stop. Find out which cylinder is failing, mark that coil and move it to another hole. Check the corresponding plug since the coil will already be out. Look for fouling, carbon tracking or any other trauma to the electrode. If ok then move the marked coil to another cylinder and retest the car to see of the misfire moves. I hope it's something simple like that.
The previous ideas are absolutely where to look, but I am just throwing this out there: The same problem happened to my car and the culprit was actually a loose spark plug in its seat. Thsi sounds so obvious and that is why it may be overlooked; get the actual plug torque specs from the Bentley or Haynes Manual and check all those first. THEN run your other checks at each cylinder and rule out any faulty coil issues. This should help you out...
Thanks for the advice! Car has been put up for a while, so i haven't thought about it too much lately. It does still happen though. I took it to BMW and they checked it for codes.. none held... So I don't know which cylinder is misfiring.. If it doesn't hold a code, is there a way to know what cylinder is misfiring? I am going to be ordering a new exhaust from BAVauto in the next month or so, so I will pick up some new plugs on the off chance it may be those.. Exhaust is all rusted out. Needs new cats and cat back.. Thanks again for the thoughts!
Another possible culprit... My son's car (323i) would do something similar in that it would make a loud pinging sound that would stop shortly after a couple of minutes... we diagnosed it down to the intake boots between air filter -> mass flow sensor -> intake manifold. They were dry and brittle and had cracks. Problem is gone with their replacement. Chuck
