I cleaned the throttle body with CRC throttle body cleaner and now the motor idles at 1000-1300 rpm. Is this normal for a newly cleaned throttle body? How can I bring down the idling rpm?

 

I remember the RPM's were higher after I cleaned mine but it went back to normal after driving it 2-3 times. I think it takes a certain amount of miles for the computer to readjust or reset itself. I wouldn't be too concerned.

 

Thank you very much for sharing that with me. I will see what happens. How many rpms was yours idling higher?

 

Maybe you knocked something out of adjustment or the cleaner needs to burn off.

 

What model and year do you speak of? Some have idle adjustment, and some do not.

 

I wouldn't jump the gun and start messing with the adjustments just yet. If it was fine before you cleaned the throttle body and didn't mess with any of the adjustments than chances are that they are fine. Like I said before, I had the same problem and it went away after a short while. I don't know if it has to do with miles driven or times started.

 

I don't remember exactly but I believe that it was idling around the same as yours and than went to 500 RPM's for a couple of days causing it to run rough and than finally settled around 800 RPM's. It has stayed around 800 RPM's for the last couple of months and hasn't fluctuated. I was concerned at the beginning but I am not concerned about it anymore since it went away and doubt that it will come back after 2 months of trouble free driving.

 

I did took the TPS off the TB by twisting it left and right to prevent it from getting wet.

I drive 1991 740 turbo in California. Would this be Bosch 2.2 or Bosch 2.4? Where can I find the idle adjustment?

 

I would put 100 miles on it before I did anything. Also check all vacuum lines and other air hook ups.

 

pretty sure a 91 turbo is LH2.4, and its got no idle adjustment, the ECU monitors the engine speed via the crank position sensor, and when the throttle position switch says the throttle is at idle, then it modulates the idle control valve to keep the idle around 700rpm.

 

Thank you very much guys. After some driving now the rpm stays at 700-1000 during idle except for when the motor just fires up by idling at 1200 rpm. I guess that is for the motor to warm up quick.


Pierce. This is what I found from the brickboard.com's FAQ.

"Setting Base Idle Specs and TPS on Bosch LH2.4-Equipped Cars3. Adjusting the Idle Speed
On the front side of your throttle body, there is an adjustment screw. Loosen the lock nut. Start the engine and turn the adjustment screw until idle is 480-520 rpm. Switch off the engine and tighten the lock nut while holding the adjustment screw so it doesn't turn."


So it seems like there is an adjustment screw. Just can't find the screw. So the absense of the idle speed screw means this 91 740 turbo could a LH 2.1, 2.2 Jetronic?