Misfire on cold start? Check in here...
Since about last year, our 2003 330i was having a problem with cold-start misfires. It would vary as to what cylinder was misfiring, but would normally happen on #5. Typically it would misfire enough to throw a CEL, resulting in fuel-cutoff to that cylinder - a re-start would usually cure the problem. It would happen once a week or so, usually when it's colder (less than 40 degrees or so).
Well, moving to more recent times, it would happen more and more often, regardless of temperature. Car has about 80K now. Things that I checked, in no particular order:
1. Coils (swapped and replaced, confirmed good spark during misfire condition)
2. Injectors (swapped and replaced, confirmed working properly during misfire condition)
3. Coil electrical harness (dissasesmble and inspect for breaks & shorts)
4. Smoke-check for intake leaks
5. Replaced intake boots (small crack)
6. Replaced DISA valve (broken)
7. Cleaned ICV
8. Plugs (replaced, all looked good)
9. CVV checked OK
There is probably more, but I can't think of it right now. I thought more and more the condition was oil related due to the temperature and re-start cure. I knew the lifters in these motors could be troublesome, and several experienced BMW techs confirmed that.
Well, when the lifters go bad in these motors, the lifter collapses and doesn't lift the valve all the way; meaning the cylinder isn't getting a complete air/fuel charge. The lifters scour the lifter bore in the cam ledge, creating escape passageways for the oil to travel instead of pumping up the lifter. Why a hardened iron lifter and riding in an aluminum bore is beyond me - but I know many manufacturers do this.
Moving to last week, I finally disassemble the top end of the engine. Sure enough, about 4 lifters had significant scouring, and 12 others were lightly damaged. The intake cam ledge was needing replacement, but the exhaust looked acceptable. That leaves me with one good cam ledge and 8 good lifters. I purchased a good used ledge ($200 vs. $460 new) and replaced the 16 bad lifters. Using the proper tools, the job took about 10 hours, which is on par with dealer quotes ($3500 parts & labor).
Lifters - $272
Cam ledge - $200
VC Gasket - $20?
Cam-lock tool - $60
Cam timing tool kit - $225
Total of about $800. From a difficulty scale 1 to 10, I'd give this a 6 only because of the time involved. If you know how engines work and can follow the TIS instructions, you can do this job.
Good news is, engine runs great in the morning. Not a hint of misfire and absolutely no lifter tick. If you have a troublesome cold misfire that you can't seem to figure out, the lifters are a good possibility.