bmwdoodle

I have a 05 545i with 50K miles. Every 1-2 months, the check engine light (codes: random misfire and increased emissions) triggers due to cold engine random misfire. I have brought car to the dealer about 7-8 times. Dealer has changed valvetronics, seals for smoke exhaust, cleaned injectors, checked plugs, checked all sensors but engine still misfires every 1-2 months. No loss in power or performance after misfire. Dealer said to switch Shell 93 gas to Chevron 93 but engine still misfires sometimes at start-up. I don't use junk stuff in my gas. Dealer said it is not due to bad O2 sensors. I have also cleaned the air throttle body and flaps. Car is super clean and is well taken care of. Dealer has checked everything but still can't figure out. Anyone has similar problems? Any help would be appreciated.

miguex

it sounds like faulty spark plugs or ignition coils.... have u checked them?

968turboS

I would start with cleaning the MAF, make sure you connect it before you turn the ignition on or else it will throw a code.
CRC makes such a cleaner. I had a similar problem with my E46 that was fixed with a quick clean. It is good to clean your MAF every few yrs anyway.
If that doesn't clear the problem, we can look into other options. Don't throw any $$ away just yet.
Is the car throwing any codes?
Raj

bmwdoodle

Yeah, dealer checked plugs etc...all good. Yes, MAF has been cleaned many times...it is throwing codes for random misfires. Is there a PCV valve? Maybe that's dirty...I have a feeling something is dirty or stuck. Again, the car does not have performance problems...everything runs very normal even after the check engine light triggers with same misfire codes. It's just irritating and dealer probably spent $15K under warranty and still can't figure out. Dealer said 545i engine is very sensitive...I think that's why bmw came up with new 550i engine a few years back.

bmwdoodle

see my response above.

njmarro

Check the pressure regulating valves. Located on the side of each head. Check out this thread Pressure regulating valve. Never had the misfire's though, but did get the increased emissions several times. Very easy and cheap fix. Hope it helps

bmwdoodle

Thanks so much..I have been looking for the "PCV" valve as I want to clean it. Yeah, I am sure the pressure regulating valve is dirty. I will clean it or replace. Thanks again.

968turboS

I think they call it CCV in BMW terms, or Crank Case Ventilation Valve. It's a common problem with other models where the engine oil temps don't get high enough from short distance driving and ultimately coke up the CCV.
I am not too familiar where this valve would be on a 545i but you might to try realoem.com and surf thru pages and see if you can find it.
Good luck.
Raj