Rough Idle / Hart starting when cold...

[Alpine003]

Car cranks just fine and starts but immediately drops close to 500rpms and starts idleing rough before it dies. It's fine if I push on the accelerator when I'm starting it or when the car is warm. Already did the normal things like checking/cleaning AFM, ICV, new spark plugs/wires, fuel injector cleaner.

Since it does it when it's only cold, I'm beginning to think it might be the coolant temp sensor. Real OEM shows 2 temp sensors in the head. Is #8 for the temp gauge and #6 the one that goes to the ecu for fuel mixture info?

http://www.realoem.com/bmw/showparts.do?model=AF93&mospid=47305&btnr=11_1505&hg=11&fg=15

Also, can anyone give me specs for checking the TPS and specs for checking both temp sensors? Haven't had a chance to get the Bentley manual yet.

Thanks.

[FL318is]

Does the car idle rough with the TPS disconnected/unplugged?

[Alpine003]

Does the car idle rough with the TPS disconnected/unplugged?

Ah, that's an easy one I forgot to do. I'll check it during my lunch break.

[Alpine003]

Well, just unplugged my tps and made it somewhat worse if not the same.

On another note, I did notice 1300rpm idle all the time after the engine is warmed up today. The only thing I did yesterday was clean the ICV and made sure all the hoses were connected and none were leaking(sprayed carb cleaner to test).

Anyone know how I can adjust idle? I didn't see any screws at the tb for adjustment. Not too sure if I wanna be idleing that high sitting in rush hour traffic going home.

Another thing I tried during my break was unplug the big vacuum hose going to the top front of the valve cover and this made the engine run smoother. Does anyone know where this hose goes to or what type of function it serves? PCV?

Thanks again.

[kramerica5000]

mine does this too. It doesn't usually die, but it has on occasion. I'll be interested to see what you find out, and will report back if my tinkering reveals anything.

[Jtuner]

My amateur opinion would say either coolant temp sensors or your ecu I've had cars with similar symptoms, my 318, it was the CTS, my 325ix it was the ecu,, good luck!

[Alpine003]

Update:

I guess after cleaning the ICV, it allowed it to pass more air and therefore the higher idle. Upon further investigation, I found the throttle plate adjustment was misadjusted by the previous owner and purposely set to idle higher to cover up for the poorer low rpm idle. :mad:

When I set the throttle plate adjustment back to normal, the car idled really rough and started dying. That's when the car finally popped a code. Code is for ICV so I'm going to replace that and see what happens.

[nicknikolovski]

Hey dude, I had the same problem. The idle was fluctuating between 400RPM & 1200RPM. Sometimes the idle was so poor that the car would just die out as you said. :mad:

I would start the car and the ignition would be really weak so I replaced the battery first and then I replaced the ICV. Now it idles beautifully.
Don't waste your time trying to clean the ICV it won't do much.

Brand new ICV cost me - $400 Australian. If your in the U.S. they're about $165-$200

[bmwman91]

Try resetting the ECU before replacing the ICV.  If it was used to the way the throttle had been misadjusted, fixing it would require the ECU to be reset for proper running.  Just unplug the battery for like 2 minutes & see what happens.

[Alpine003]

Try resetting the ECU before replacing the ICV.  If it was used to the way the throttle had been misadjusted, fixing it would require the ECU to be reset for proper running.  Just unplug the battery for like 2 minutes & see what happens.

This is one of the first things I've tried after cleaning my ICV. I should be getting a new one in sometime this week so I'll install it and report back.

[Alpine003]

Update: Got the new ICV in and unfortunatly it still idles rough but it does stay running when cold.

I did replace the intake boot and a couple other vacuum hoses too. I will probably take off the intake manifold and replace the rest of the vacuum hoses that go underneath and while I'm at it, replace the coolant temp sensor and clean the injectors.