Violent misfire underload - N62 - Weak coils?
 

I'm curious if any of you guys have experienced this particular problem with your N62 4.4s or 4.8s. This occurs mostly when I'm on the highway and is triggered by heavy acceleration. When driving with it running fine it will suddenly (usually right after giving it a lot of gas) go into what feels like a violent misfire under load. Its engine related because it will do it both in neutral and drive.

It shakes really bad and does that "brrr" type vibration when you try to accelerate. If I slow down and just cruise for a few minutes it will usually level out and be fine but then do it again a few minutes later. Its extremely frustrating.

I bought all 8 ignition coils because I've read that the 00124 coils in our cars can get weak and not kick a misfire code but I will return them if anyone has other ideas. It seems to be doing it even at low speed now but not as drastically and possibly in my mind because this shit is driving me up a wall.

Car has a brand new genuine MAF, CCV hoses, CCV caps, Valve Cover gaskets, and plugs. No vacuum leaks.

Any ideas? Am I on the right track?

I have the preTU N62 in my 545i and I have read in 750i forums that sometimes you need to charge the battery up and one guy today switched to Shell Gas and that cleared it up.

If you don't get any help here after awhile I check the forums in the E60 550i and E65/E66 750i forums as well since they pretty much have the same engine.

Battery is charged up.
Gas has been switched from Hess to Mobil to my local station I always used with no improvement whatsoever.

I might try the other forums. Thanks

No vacumm leaks can be possible fuel pump on its way out, mine would do it at idle sometimes i didnt think much of it, till i replaced the pump.

No stored codes and no engine light.
I've never been so desperate for an engine light to come on in my life.

That makes sense. I'm going to change the coils because I already dished out the cash but if that doesn't resolve it I'm going to have to look into the fuel pump more (at a shop with the proper tools).

Depending on what you are using to read codes you may not be seeing error codes for your issue. Are you using BMW diagnostic software? If not, I would have an Indy shop with BMW software check for error codes before throwing more parts at the problem. That said, coils problems are likely to show up when engine is under hard acceleration.

I had this problem in a 4.6is.

It also did not register any codes at first.

What I did was go to a deserted stretch and really floor it.

This made the problem cyl misfire enough to flicker the cel and store a code.

From there, you can diagnose if it is coil/plug by the usual methods like swapping parts between cylinders and repeating the test.

I am fairly new to N62 engine but I have seen this problem on hundreds of cars because of my work.

It may have many reasons, mostly within the ignition system.
- Before going for coils, spark plugs must be taken out and observed.
Oil leaks inside the spark plug tube is the most common reason for this problem. When the fuel become rich as you floor the pedal, resistance between spark plug tip and electrode rise up and spark want to follow oil and go to engine body, not inside the cylinder.
- Old or spark plugs with huge gaps can also create the same problem. Distance between electrode and tip filled with air and gasoline mixture, resistance changes according the mixture level.
- When spark plugs are checked it is better to try the Coils but you already have them:) It is always good to have new coils. When we encounter coils worked long time with oil around, they get broken. Necessary to replace.
- I have seen similar problem caused by cam sensors or some other sources too. But above checks are very easy and need to do before to move forward to other searches.

If you can take out your sparkplugs and send photos here it might be helpful to identify the problem better.

regards

When is the last time you changed out the fuel filter?