rough idle at cold start HELP!

i have a 1994 325i when i first start the car up in the morning the rpm drops under 1 grand and then flutters up and down under 1 grand almost like its about to stall and then the rpm raise..... im not sure if my intake is dirty or i have a bad o2 sensor or if i have a vacuum leak but if i hold the rpm at 1 grand using the pedal for a few min the car will idle fine after i do that and the problem goes away completely it drives normal accelerates fine there is 170k on it i replaced spark plugs at 150k please give me your insight!

Probably a dirty idle control valve.

what else could it be?

Vacuum leak.

Could also be the fuel pump or fpr(fuel pressure regulator). My car does the exact some thing. I haven't fix the problem yet, as I'm having to spend my money on other things with the car. But a member on here, I think his name was dano, had this problem too. He changed his fuel pump and it solved his problem. Look up a you tube video on how to check for faulty fuel pumps and fpr for the e36.

You could also try to clean your idle control valve to help rule out the problems. The icv is located under your manifold. No, you don't have to remove the manifold to get to it. Although it would make it that much easier. I'm sure there's a how to in stickies or on you tube.

Start with the simple and cheap and progress outward. I would start with cleaning the MAF, ICV and throttle body. If no help then check intake boots, CCV and hoses, disa for operabilty and small cracks. Next check your spark plugs and coils. Change fuel filter. Still no good, check the fuel pump and fuel sender units. Still no good maybe bad fuel injector.

ok thank you for all the help its weird how after a few min of running it goes away

don't believe disa was used on non obd2 cars, tho...


but i agree, start with the simple things first. cracked intake boots, vac lines, and plastic nipples. clean the throttle and idle control solenoid (good maintenance, anyway..), and go from there.




good luck.





df

Ah, my bad, I have my e46 on my brain. You are obviously correct, DISA is on the OBD2 cars, mea culpa.

I thought a rough idle at start was normal for our cars. My m3 does it also. Goes away after 15-20 seconds.

Depends on one's definition of "rough idle". The symptoms the OP is describing are in no way normal, however.

Originally Posted by ZeGerman

Depends on one's definition of "rough idle". The symptoms the OP is describing are in no way normal, however.

True, or maybe there is just something wrong with mine too.. lol.

I think the majority of cold idle issues emanate from either dirty ICV or vacuum leaks. Most likely small vacuum leak somewhere.