Engine temp sensor controlling idle? Wrong sensor?

[scabzzzz]

So after my long drawn out troubleshooting with my warm starting issue a while back, I'm slowly noticing little things that are wrong. In the process, I replaced the AFM, computer with MarkD, both reference sensors on bellhousing, all ignition parts and filters, temperature switch, and temperature sensor, Bosch O2 sensor.

Now the question. If I have the wrong temperature sensor, will it edit my idle attributes to the computer? My cold starts are flawless. Warm starts are good and consistent. It idles about 200-300 RPM more than I would like. At times it will settle down to 650-700 rpm like after a cold start but will ADJUST ITSELF to about a thousand, like it wants to idle properly but gets told not to. I bought the temp sensor from O'Reillys warehouse so I didnt get it from a reputable BMW parts supply. Would this make a difference? Or are the sensors all the same? My idle control unit adjuster screw has been tampered with but doesnt really do anything but make the car idle higher when I adjust it up.

Thanks for reading!

[AndrewBird]

Not sure about the sensor, but it sound like you might have a vacuum leak somewhere. Check the accourding boot connecting the AFM to the throttle body. They often tear in between the bends.

[scabzzzz]

Not sure about the sensor, but it sound like you might have a vacuum leak somewhere. Check the accourding boot connecting the AFM to the throttle body. They often tear in between the bends.

I didn't even own the car yet before i had an order placed on Worldpac for the basic necessities like the intake bellow. So its minty fresh.
Thanks for the reply.

I've taken off a few key hoses and visually inspected for cracks and what not. Have not found any yet. On the eta, i know that the idle control box and the idle control unit in conjunction with the throttle position sensor control idle speed. The Bentley basically says I have no control over adjusting idle.


But if the sensor is telling the components the temperature of the coolant is different than what it actually is, it would adjust ignition and air/fuel ratios accordingly correct?

[jlevie]

The engine temp sensor will affect idle, but not in the way you describe. A varying idle will be the result of; an intake leak, misadjusted throttle, misadjusted or bad TPS, ICV problem, or on this car an ICM problem.

The first think I'd suggest would be to check the operation of the TPS and make sure that both switches are working. Then adjust the throttle & TPS correctly. The procedure for that is in the Bentley manual. If you don't have the manual it goes like:

1) With the engine at normal operating temperature, disconnect the ICV and adjust the throttle stop for a 900rpm idle.

2) Adjust the TPS so that the idle switch closes when the throttle is 0.020-0.040" from the stop. You'll find this a lot easier with the throttle body off the car. And while doing that clean the ICV with carb cleaner.

[scabzzzz]

More high fives to Jim..

Will do that this weekend and see what happens.