RPM dropping when heating up

[martmode8850]

ok... my ride is the 318i valvetronic and is only about 5 months old... 7555km... just noticed this consistant thing...

cold start. temperature gauge starts heating up. RPM about 700-800. when the temprature needle just about hits the first white mark before the mid range, the RPM drops to 600 rises to 800 for three times in a row within a time frame of about one-two seconds. after that, it stays 700-800 till normal mid range temperature. is this the rough idling we all know?

 

[MRacer77]

Re: RPM dropping when heating up

I think its pretty normal. Only if it rises and falls and rises and falls then it dies, then you should be worried. Then maybe it will be a idle sensor or crank position sensor problem. but since your car so new, should not be the case.

 

[TobyNik]

Re: RPM dropping when heating up

Dude

I suggest you get it checked at PML.

318i Valvetronic should behave as follow for cold start:

- Crank, rpm will start at about 1000 with the signature "tiak" "tiak" "Tiak"....sound
- After 1 to 2 min, "Tiak Tiak Tiak...." sound would be gone and rpm should drop nicely to 800 to 900 range with Air-con on. No aircon, rpm lower
- At no point in time, car or engine should vibrate.

For valvetronic 318, usually experience slight vibration only after you "whack" the bugger driving enthusiastically. But nothing violent.

Cheers!

TobyNik

 

[bmwF1]

Re: RPM dropping when heating up

It is quite a common problem among the 318i valvetronic and it is most likely the ignition coil giving the problem. Go back to pml and they will replace the ignition coil for u under warranty.