Ignition problems (thanks for help!!)

[Vader M3]

well, so here is the scoup. 97 M3. The first five minutes of the day, car runs like a champ and there are no hiccups. Within 5-10minutes I start to get a few sputters and then it acts like it's got a coil or two out, sometimes so bad I can barely accelerate uphill like in 4th gear at 40mph. so like something happens when the warms up and goes closed-loop perhaps..
I had Bav Auto Hi-Perf coils in there and swapped to my original ones. same thing happens. Runs fine at first, then cruddy. It sounds very much like the boxster STi engines to be honest.
So I did some research and decided to change out the Cam position sensor since car has 148k miles. Didn't do the trick. (btw, I always have a "vanos mechanically stuck" code--but car seems to run fine in that regard when it does).
My codes have been "misfire Cyl 4" and the other code for "Cyl4 coil". IIRC this happend with both sets of coils. While car is idling, sure enough the #4 coil doesn't make a difference when I unplug it. So then I swap #4 with #5 and drive around. first it seems ok, then after a few minutes same thing, only now it's telling me cyl #1! so I check, sure enough--coil 4 and 5 make a huge difference when unplugged, and coil#1 does not! so if anything I'm getting it from #'s 4 and 1. is this indicative of a coil driver in the ECU? does it have 3 igniters? one of which does #'s 1 and 4?? so stumped here. thanks for any advice!! I'm going to have ECU supposedly checked next..

[Balthazarr]

It does appear to be a closed loop condition, so ECU is suspect.
Maybe a shorted injector is pulling down the driver circuit?
Check the resistance of the injectors.

[Vader M3]

thanks! I checked injectors and they all give me the same resistance (15 out of 200 setting on the meter?? not sure what that means, but they're all the same). So one day it might be cyl #1, another day cyle #4, and today it was cyl #2! so it's different all the time, and I'll check cylinders 1 and 4 when #2 is missing, and now they're fine! so when idling it always seems to be just ONE cylinder missing. When driving underload it can get worse though.
I can then unplug #2 while it's running--no change---then plug it back in..voila..it idles normal. drive it 30sec, doing it again. weird stuff. I've owned 4 E36 M3s (although this one highest mileage) and I've never seen this. very frustrating! thanks again for any help gents--I've been doing lots of searches and will be checking coolant temp sensor next I suppose (can this do this??) and vacuum leaks next.
PS, MAF will stall car if I unplug it. It doesn't look dirty either. I sprayed it with carb cleaner but no change. thanks!

[Balthazarr]

Get it out and run it in 3rd gear on the fwy for a while around 4300rpm.
See if that helps.

[thejlevie]

A problem that doesn't show up on a cold engine (open loop mode), but does on a hot engine (closed loop mode) is most likely to be something that upsets the A/F ratio. The most logical candidates for that are an intake leak and/or bad CCV and/or bad pre-cat O2 sensors.

[Vader M3]

well, I've come to the end of this saga. I post here so people has this on record in case anyone goes thru this silly little hair-puller.
So I changed coils around--nothing, but would still jump around as to which coil would miss. sometimes it could be two missing.
Checked resistance to fuel injectors--all the same.
changed the cam sensor--nothing.
changed the crank sensor and harness w/ 4 connectors---nothing.
finally, messing around with coil #1 a bit, I realized it started idling normal. Drove it, 10sec later, same thing. missing.
when I went to plug in my fault code reader, I noticed when I'd frustratringly take it off (and shake the connector to it a bit), the car would sort of catch itself the last coil and start idling normal again (what the??). I'd wiggle it again, and the car would change!!!
I'm doing this in the dark, on the road under a lamp post, and notice there's another connector behind it. I wiggle it, car shuts off! I'm nervous but also very excited at this point. Get it started again, bring it back in garage, it's the darn coil harness connector behind the OBD2 port that wasn't ever put on tight!!!!!
so I tighten it, voila, car runs like a charm. Embarrassed, to say the least, but even though I dumped $250 in sensors and several hours of work (been like this for a month!), I'm mighty happy at the moment. :D

guys, thanks again for the help though!

[Balthazarr]

Glad it was a simple fix. lol

I'll file this away in my prion ridden memory banks.
Which OBD2 port is this you mention?
Please find or take a pic and point it out.