Cold start missfire

[Norcal]

I've been having "issues"... a few months ago my car started chugging and bucking, and missfireing on cold start. It only lasts for a couple minutes. If I let her warm up until the idle drops it's pretty much gone, but still not perfect. I did get a check engine light a month ago, but it went away in a couple days. I took it to Matt at Peter Pan a few weeks ago, and he replaced the plugs and integrated coils... still happening. I got another CEL today after work. The car also feels down on power. Doesn't seem to be an exhaust cam issue. Any ideas? Similar symptoms? Anyone? Bueller... Bueller?

[macfly]

My thought is Vanos, MAF or O2 sensors because those are the only other things I can think of that could cause that, but all of those should show up on Matt's diagnostic machine, so honestly I have no idea!

[KenZ8]

I just saw a new product in Roundel called Bavarian Technic which allows for real time data logging http://www.bavariantechnic.com
I don't know anything about the product or its reliability, but was very interested in the ability to review the car's performance and analyze any problems at my desk. This may point out an intermittent problem if you can capture it. At the very least, you'd get a cool "Peake" type reader and code resetter. One negative is that it seems to be PC based, not Mac.

[Norcal]

Matt offered to come to my home with his gear (computer?) to help diagnose it. Above and beyond service! He did have the car for a week at PP, and couldn't find the problem, so is committed to getting it. Hopefully we can do that soon. I'll keep you posted. I did go onto the M5board and find some info, mostly related to MAFs/02 sensors, and a possible reflash.

[Z8Mania]

My ***GUESS*** is its either 02 or MAF sensor because of the fact that it improves with warming up.

[Norcal]

How long are MAFs good for anyway? I'm at 11 years and about 40k mi.

[Z8Mania]

In my experience you're way over. Usually it's around 20k miles/ 3-5 years depending on your environment.

[Norcal]

For which?

[thegunguy]

I don't think you can do better than having Matt come sort it. All the sensor stuff makes sense, but they should throw codes.

[Z8Mania]

For the MAFS. 20k miles / every 3-5 years.

[boomster]

Ian, your description of the poor running characteristics of your car two years ago sound very much like what I am now occasionally experiencing. Car bucks and chugs for the first minute or two, then seems to smooth out and runs fine. Particularly after a very short run (2-3 minutes) followed by a restart after an hour, the car almost feels like it is going to die, but then smooths out and runs well. Was your issue related to the MAFs? If so, did you address this by replacing the entire MAF unit, or just the sensors? My car just turned 37k, and to my knowledge still has original MAFs.

Bill

[Norcal]

Yes, does sound exactly like mine. I think I was at about 41,000 mi at the time? I seem to recall it was time for all the exhaust cam sensors, and we did not do the mafs. I really should, if I haven't already! Contact Matt at Peter Pan, and ask him to check how they fixed mine.