Rough idle at startup

[morkm]

Quick question.

I have a 1997 M3 Sedan with only around 60,000 miles on it. I've had the car for 2 years now and have a somewhat ongoing problem. Specifically, when I start the car from cold, it engine runs very rough for at least a 60-90 seconds. During that time, if I try to drive, the engine wants to cut out when I press on the accelerator, with the revs dropping way down.

I find this even on 'cold' starts in afternoon, in the middle of summer.

Am I right in thinking that this has to do with the engine being high compression and therefore it needing to warm up, or is somthing more going on?

Yes, I know I can have it looked at by the dealer, and I do have it serviced by the dealer. I feel pretty confident that if there were any problems in the engine (with air leaks, compression problems, etc) the dealer would have been right on it and eager to fix it and thus make more money.

Anyway, any and all suggestions welcome.

Thanks.

[Jared at Pelican Parts]

I would first try reading the codes and see if that gets you anywhere..

http://www.pelicanparts.com/bmw/techarticles/Mult-Code_Reading/Mult-Code_Reading.htm

[jds7717]

Hmm... maybe it's the air in Austin, TX? I have notice this problem for a few months now. My car does not produce any fault codes that are visible. In my experience the idle speed will dip down to about 500 rpm a few times in the morning and if I try to drive it before it settles down the car will die. I've just learned to live with it but it is a major PITA to have to wait that long. Especially when my girlfriend asks why we are waiting to go.

Jeromy

[Jared at Pelican Parts]

Im suspecting perhaps something with the idle control system....

[jds7717]

One detail I left out is that I have an aftermarket cold-air intake and the Shark Injector software. I'm not sure if that has something to do with it or not.

If there was a problem with the idle control system, wouldn't this happen all the time (while the car is at idle)? This only happens to me from a cold start.

[Jared at Pelican Parts]

Sorry, was thinking something different from what I was typing. (tends to happen to me a lot)

The cold start system works off engine sensors until the O2 Sensor warms up. It could possibly be a bad sender somewhere.. Perhaps the coolant temp sensor..

[morkm]

Thanks for the info. My car is stock and everything checks out normally (at least as far as I've heard on normal dealer maintance....and I know these guys would jump at a chance to fix/replace something if it was even 'maybe' out of whack).

I'll assume it's just the high compression engine needing to warm up before it will idle correctly and live with it.

Thanks again.

[Jeron]

I have the same cold start problem but it usually only in the cool morning, thats 75 here is DFW, TX.

My mechanic said I had a bad camshaft position sensor code about three weeks ago, but yesterday when I checked for codes with a Peake reader there were none.

If I find out anything I post it.

Jeron
97 M3/4
01 330

[Jeron]

My research has found that a sticking ICV (idle control valve) is usually the culprit. I plan to clean mine tonight and I'll let you know if my cold idle problems are fixed in the morning.

O2 sensor is the next cause but I think it usually yields fault codes, which I don't have. The next two causes are cam position sensor and coolant sensor, which also yield fault codes.

Jeron

[BMWCowboy]

Make sure ur secondary air pump is working>>it supplyies the needed air on start-up when cold>>and they do go bad~

[Jeron]

I cleaned my ICV and here are the steps. This could easily save you an hour on the job.

Remove the airbox, MAF sensor tube and flex boot
Disconnect the wire that runs in front of the intake opening to make room for you to work. The wire harness is held on with a spring clip so use a flat head to pop the clip out.
Put tape over the shiny, and sharp, worm clamp below the intake so you don't cut your hand.

The hose that ran into the bottom of the flex boot goes to the ICV. You can't see the ICV from the top and only barely see it from below, but don't even bother getting under the car.

The dip stick tube has a bolt at the top to keep it steady; this bolt is on a bracket with two others. These three bolts need to be removed. You will need several different socket extensions to get the bolts out easily, or you could substitute a lot of patience. I used a 1/4" socket for most of the bolts.
Behind the bracket is the ICV. It has a wire harness on the firewall side. Remove the wire harness but don't loose the spring clip. It has the same type of spring clip as the first wire you disconnected.
The ICV simply friction fits up into the intake manifold. Reach under the intake manifold and pull and twist the ICV downward to free it. Use the hose coming from the ICV for extra leverage.

Test the ICV for resistance across each pair of pins. The resistance values are in the Bentley manual. Clean the ICV with carb cleaner and put it back. Try to get as much upward force as possible when friction fitting it back into the manifold. Don't worry the bolts will hold it in place.

It took me almost 3 hours but 1 hour was finding the ICV and another to how to get it off. You can only see it from one very specific spot under the car.

After all of that my rough idle problem is not fixed but I forgot to check the resistance on the ICV. Actually, I did test the resistance and I think it failed one of the readings but I didn't know what they should be when I tested it so I'll be doing this again and retesting.

Next I'll test the secondary air pump.

Good luck.

Jeron

[MikeM3]

I had the same issue on my 99 M3 coupe. Local BMW dealer said they could load a new program in that would eliminate it...AND IT DID!!!

Totally went away and runs great.

[nightkrawler]

m3 are prone to idel surging and other idle problems, here is a clip i found by jim conforti

"From digest.v4.n830 Thu Jul 11 14:38:44 1996
From: Land Shark
Date: Thu, 11 Jul 1996 14:00:50 -0600
Subject: E36 M3 Idle Surge

Yes, it's a known problem...

Don't let them fool you ..

It's NOT a big deal however ..

The reason it happens is that there is code inside the DME that does NOT engage the idle circuit until the VEHICLE speed is below about 1.4 MPH ..

This causes the speed to surge as the EGO sensor controls the fuel, but the ICV does not regulate the AIR .. hence the surging rpms ..

The fix is to reprogram the EPROM, but BMW has not chosen to do that, instead they have a kludge fix that interrupts the A signal from the Instrument Cluster to the DME when the clutch is pressed in ...

Jim

PS: Yes, if someone has it occur FREQUENTLY I could ship you TWO eproms to try,

of which ONE would fix the problem for you ... it doesnt happen often enough for me at 4800' alt. to diagnose! "

[dboyles]

Originally posted by MikeM3
I had the same issue on my 99 M3 coupe. Local BMW dealer said they could load a new program in that would eliminate it...AND IT DID!!!

Totally went away and runs great.

Anybody know how much the dealer charges for this service?

[Metroporter]

I am having the same problems relating to a stumble in the RPMs when idling after a cold-start. I have not yet invested in the diagnostic tool to check for codes so I don't know where the best place to start would be. It sounds like it could be a myriad of things. Has anyone had any luck pinpointing the issue? Thank you!

Btw, I have heard the water pump bearings may bind on occasion causing this issue. I don't know if that could actually cause the problem in the first place, but in any case, I recently (3k miles ago) replaced my water pump so I cant imagine that being the issue.

[HGS]

Originally Posted by BMWCowboy

Make sure ur secondary air pump is working>>it supplyies the needed air on start-up when cold>>and they do go bad~

The SAP pumps air into the exhaust manifold to keep the rich fuel mixture used when the engine is cold from ruining the catalytic converter. It plays no role in supplying air to the combusiton chambers. In my car the problem was solved with a new idle control valve because I took it to a mechanic who would rather sell a new $150 part then clean an old one.

[Metroporter]

I have an E36 (M52 Engine) 1997 328i. The problem I am having is the idle is running too low. If I push the gas petal to raise the RPM, the car runs fine. Without the extra gas, the engine dies. I ran an OBDII on it and it threw a code, P0505 "Idle Control System Malfucntion." Before I start tearing stuff down & ordering parts, I wanted to see if anyone else had a determination on this? Thank you!

[bighead]

I know this is a very old thread but I am having the same issues. Does anyone have an answer or known part that will fix this? I have heard replace the ICV or take it to the dealer and have them flash the DME. Any suggestions or ideas?

Thanks

[Jat007]

I am too having the very same issue on starting. It always in the morning or the car has been parked for several hours. The stumbling only lasted for about 30-40 seconds. The car does gets about 21.4 MPG, which is not bad for a 1997 328ic with the top down.

Thanks,

Jay