Idle problem, what could it be?

[1990LXDropTop]

My car has been idleing fine since my h/i/c swap for months now; that is until now. Most of the time now it usually idles fine, but every now and then it will start idleing at 1500rpms+++ and won't go down unless I shut the car off and re-start it. Could this just be a bad IAC sensor? What else could it be?

 

[1990LXDropTop]

ttt

 

[jimilane]

Well, they say it's usually the Throttle Position Sensor. I know that they will check fine, and can be set fine, but still have a problem.

Also, if you have messed with the adjustment screw for the throttle, it will also tend to hold or raise the RPM during shifts.

Most everyone sets the gap on the throttle adjustment screw to throttle blade plate to .010 then turn the screw and aditional 1.5 turns. Also some set it to .002, then turn a half a turn. You just need to make sure it doesn't bind.

Jim

 

[DMAN302]

I found a sneeky vac leak after my 200th inspection of vac lines..also check the hego ground for the o2 sensors, and check the PCV grommet for any sign of slack fit. Clean the standard parts like TB and IAC, along with MAF and reset the TPS