Very rough idle at cold startup

[m3f_snopro67]

:hmm: I recently bought a used 1997 M3 coupe it has 52,000 miles and ran perfect for the first 1.5 - 2 weeks.

However recently it has developed a very rough idle at cold start up, (sitting overnight in garage, home @6pm...startup @6am the next morning) Once the engine runs for 1 - 2 minutes its fine



If you put it away at 10 pm and start it the next day at 6am it is fine



Warm startup is fine.



I changed spark plugs - no difference

Any ideas???

[m3f_Sirius_880bd69485]

Normal.



Its funky programming in the DME that causes the engine to run rough. Theres supposedly a software update, which I applied to my car, and saw minimal results.



Beemertek may have a more technical answer than I can provide.

[m3f_bmw4life13_0098c1d2b1]

Many if not most e36 m3 owners have a rough idle on cold startup. I wouldn't worry about it.

[m3f_dboffa_1e4798cde8]

My idle is crazy on startup sometimes. The other day it idled around 1500 rpms before finally dropping. It got me a little worried, but once the car settles and I drive it everything seems fine.



I do think I need to clean/replace my idle control vavle. My idle right now sits at about 600, which seems a little low. Any other possible causes of this?

[m3f_Sirius_880bd69485]

Heh, you think thats bad.... some of the E46's idle bounces all over the place, and even stalls on a cold start...

[m3f_rocket808]

thats life with an m3...get used to it.

[m3f_rustamabd]

Go get the DME update from the dealer for free (it's a hidden SIB, I will see if I can dig the number later).

Then get 2 new pre-cat O2 sensors and NGK sparks. Also clean the idle control valve.

Should be fine after that.

[m3f_dboffa_1e4798cde8]

My E46 had a pretty rough idle, so the M3's was really nothing new. It just seemed low.



I'm going to do O2 sensors soon, and then the idle control vavle. Sparks were done around 10k miles ago so they're good.



I like to think of it as one more thing that gives the car "character".

[m3f_99cosmoM3]

I spoke with my bmw dealer about a dme upgrade and they said they could do it but it would be $50 even though my car is CPO. What is the $50 about that they said I have to pay every time I want something fixed/changed that is covered under CPO. Are they trying to rip me off or are all bmw certified places charging this?

[m3f_Sirius_880bd69485]

The $50 is like a co-pay for insurance.



Say you have $1000 worth of work to do, you still own $50.

[m3f_rustamabd]

Never heard of a copayment. All my warranties expired long time ago, and still the dealer performed SIB 12.02.99 for $0.00.

I didn't get a loaner though since there weren't any available. So maybe you may need to pay at least something if you want a loaner.

[m3f_Sirius_880bd69485]

It depends on the service. Most are like 50 bucks. Probably for the maintance plan.

[m3f_rustamabd]

You know what? I'm looking into the current TIS and can't find the damn document! SOB's deleted it!

Anyway, you better hurry up and get your DME updated for $50 or else it may no longer be possible.



I swear there was a SIB 120299. Here it is (from my 2001 archive):



http://home.columbus.rr.com/rustamabd/temp/SI%20%20Motorsport%20Engine%20runs%20rough%20on%20 cold%20start.pdf

[m3f_Sirius_880bd69485]

There is. I just looked it up on BMW's TIS online.



What you have access to and what I have access to is different.

[m3f_rustamabd]

Can I have online access to TIS too?