when cold starting it wont stay idaling unless i hold the rpms up to 2000 untill the service light goes away.
then it idals and runs fine, untill i shut it off and start it agian and its sluggish for a half block or so. then its fine.

whats the problem?

 

ECT might be bad.
Idle motor might be dirty.
Throttle body might be bad.

Also year and model would be nice.

 

I agree with Tech, I had the same problem but not really to that extent. I fixed it by removing the iddle control motor (really easy, it only has a wire connector and two vacuum hoses connected to it), then cleaned it really well with carb cleaner. I then bought some throttle body cleaner and sprayed almost the entire can right into the throttle body by removing the main intake hose and spraying the cleaner onto the butterfly valve with the car off since the AMM won't allow you to do it with the car on. You have to spray for ten seconds while moving the butterfly valve back and forth. Then turn the car on and leave it on for about 30-seconds (it might be hard to start at first but it will start eventually)... then repeat until the can is empty. Be carefull not to spray any cleaner on wire harnesses cause it will melt them. Then, the last step in the cleaning list would be to seafoam your intake... follow this link for that.... http://forums.turbobricks.com/showthread.php?t=35053

I have done the Seafoam trick a few times and it will not damage your car and it is oxygen sensor safe. Your iddle will be much smoother and hopefully this will fix your starting problem.... good luck.

 

sorry 1991 740 turbo wagon

 

i was also told turbo has low boost

 

Yeah. I have a 745t aswell. They only run 5-7 psi.

 

Try cleaning the throttle body and idle motor and take it from there.

 

also when i bought it it had papers in the consle that said the o2 sensors were out of range what does that mean?

 

You can test it. Find the single wire and connect the positive side of a meter to it. Then ground the other probe and watch the voltage with it running. It should sweep from 0 volts to 12 volts.

 

My 1988 turbo sedan did the same thing. Try unplugging the AMM (the wiring harness on top of your air cleaner box). If it starts and runs then it's the AMM. Replace it.


There seems to be a common trait amongst bosch parts from personal experience. I've had to replace my AMM and re-solder both my fuel pump relay and my light out indicator relay. A failing relay could deceive you into looking for a bigger problem. Not that the air mass meter is a relay, but... yah just try it.

 

Also with the continuous idle system you have a throttle position indicator that should click as soon as the throttle body is opened beyond idle. Check this by moving your throttle by hand at the engine and listening for an immediate "click". If you hear no click then you should look in to adjusting it. That's not hard either.