GTR81

My 1988 Convertible has a fast idle, 1400 RPM. Per the "Workshop Manual" this can be corrected by turning the Air Adjustment screw on my non-turbo 13B engine. Unfortunately the screw won't budge and I am hesitant to apply too much pressure. The car sat for two years, but I got it going again this summer. Should I soak the screw with penetrating oil? Any suggestions welcome. BTW, I know the problem is probably with the TPS, but wanted to check the "easy" part first. Thanks again.

j9fd3s

iTrader: (3)

yeah try the oil. you're adjusting the screw on the top, yes?

GTR81

Yes it is on top, I'll start soaking it and let you know. Thanks

mazdaverx713b

iTrader: (91)

The problem may not lie with the TPS. Often times a throttle position sensor that is out of adjustment will cause a surging idle.
You may have a faulty coolant temp sender that's tricking the ecu into holding the engine in cold start enrichment and causing a high idle. Likewise, a faulty thermowax unit or binding throttle linkage or cable can cause a high idle. And finally, with the cables, if your car has cruise control, check to make sure the cruise control cable is not binding or that the actuator is not sticking and causing slight tension on the cable. This will also raise the idle.

Finally, I would do a thorough check for vacuum leaks. A vacuum leak will certainly cause a high idle and at the age our cars are at, many of the vacuum lines are very brittle.

GTR81

I should have given more detail. On cold starts the idle is 800 after it reaches operating temp it jumps to 1400. I appreciate all you input and will follow it as I track this down. Thanks again.