1993 940 n/turbo high idle

[anotherMattsDad]

I have 1993 940 non turbo with around 200 k (it was involved in a bad accident, totaled and rebuilt, son ok) t boned left front wheel straightened out, alignment good, runs great looks great. Son's college car. Idles ok 900 for 5 sec then goes to 1700 as a base idle NO CODES ( it does this started cold or hot) temp guage appears to be working, throttle body is clean, you can hear the tps click when opening the throttle about 20%, if you disconnect the isc actuator/motor the idle drops to around 500 rpm and does continue to idle even cold. Any ideas? Is there a default speed for the isc to go to if unplugged? Is there an adjustment on the TPS. Thanks
PS the throttle body is on the stops and the linkage is free the TPS took a good bump from the master cylinder

[billofdurham]

The throttle position switch (TPS) can be adjusted but if the problem did not occur until after the accident I would suspect that the TPS has suffered damage, especially as it

took a good bump from the master cylinder.

The TPS was not designed to withstand such treatment.

The TPS is a simple device. At either extreme of motion of the TPS, an internal switch is closed and you have continuity between one outer connector and the middle earth (ground) connector. Disconnect the switch connector and jump from one side connector to the middle earth connector. If idle returns to normal, then the switch is at fault. The switch is not repairable.

If the switch is working correctly it can be adjusted.

1. Remove the throttle body from the car and loosen the TPS adjustment screws
2. Hold the throttle plate and keep it from moving. Rotate the TPS clockwise, then counter-clockwise until a click is heard. Continue rotating until it stops but does not cause the throttle plate to move. This can best be done by inserting a .25mm feeler gauge between the lever and the adjustment screw. Secure the screws.
3. Proper adjustment is obtained when you open the throttle plate and insert a feeler gauge at the throttle stop screw.
When you close the throttle against a .45mm feeler gauge, no click is heard from the TPS.
When you close the throttle against a .15mm feeler gauge, a click is heard.

Bill.

[anotherMattsDad]

Thanks Bill,

You hit the nail on the head. It was a bad TPS, tested it and the circuit as suggested, replaced TPS and set up as you suggested and it works great. It can be done by only removing the cruise vac diaphragm and it's bracket rather than the throttle body and hoses. (as my throttle body was just cleaned) less than 30 minutes time to do it all.

Thanks Again,

Rick

[billofdurham]

Thank you for the update.

Bill.