[Aldergrove]

This vehicle gives excellent fuel economy.

However, after warm up after driving for 20 min, the idle will dip below 600RPM and just about stall before it self corrects. Before I adjust warm idle to 900 rpm on the trottle body I wanted to ask if the AIS motor could affect the idle and should have the throttle body passage blown out with combustion cleaner. TPS is perfect... no hesitation. New head and all`s well... just this minor quirk that I must adjust before winter sets in.

Speedo works but odometer sometimes stops

Speed sensor¸

IS it possible on the 90 that the speed sensor is affecting the computer to tell idle to dip

Your thoughts...

 

[John Wood]

Since it dies after you are stopped, I think we can rule out the speed sensor. I suspect the problem is with the AIS motor or more likely with the pintle being either packed with carbon, or gum in the pintle drive mechanism.

Over the years, I have had good results with removing the entire throttle body and totally cleaning all passageways and the AIS motor pintle using carb cleaner and compressed air. Be sure to remove the the TPS and TB temp sensor since they have plastic parts that can be damaged by carb cleaner. Also don't let the carb cleaner spray back in your face (I've done it and it is not good).

One other possibility is a poor seating EGR valve or one that is sticking open more than it should (or just slow to close). Your vehicle may not even have an EGR valve, but check for that possibility.

You probably know that removing the TB can result in broken plastic tubes and tees that have become brittle from years of heat. Be prepared for that nuisance.

Hopefully the throttle stop screw has not been adjusted since it is factory set and should never be touched.