Ok, I have done a few tests to see if I can fix this, but still no fix. The idle goes up and down when in park. It ranges from 1000 to 1500 rpm and only does it when it is warmed up. I have cleaned the IACV, tightened the FITV, cleaned the throttle body, and bled the cooling system. I also sprayed carb cleaner around some of the typical exterior vacuum leak areas to see if there were idle changes, there was no change.

I unplugged the IACV electrical connection and that took away the erratic idle, and put the idle where it belongs. Does that mean that the IACV is the issue, or could it still be something else? Is there a way to fix an IACV? Should I just try to clean it again?

 

When you unplug the IACV, the idle should drop down to about 550 or so, & that's known as the BASE idle. If the base idle is set too high (like yours sounds like) that could be the problem.

Find the idle-air adjustment screw, recessed in a hole above the throttle bore. Warm up the car completely, let it idle with ALL loads turned off.

1 - Unplug the IACV & adjust the base idle to 550 rpm.

2 - Turn it off, let it cool down, plug the IACV back in, reset your ECU.

3 - Start the engine without touching the gas pedal.

4 - Let it warm up completely without touching the gas pedal.

 

Thanks, I will try resetting the base idle, to see if that helps.

 

I adjusted the base idle, it was set at 1000 rpm Hopefully that solves the problem, I will let you know after it cools down and I can reset the computer and start it up again.

 

Thanks, that fixed the surging idle. Now when the car idles when cold it is low and rough when in gear. Any ideas?

 

Look for vacuum leaks - fix em.

Check to make sure the actual throttle plate closes completely.
- throttle cable MUST go slack.
- mechanical throttle stop only just barely prevents it from wedging stuck closed.

If you have to fix any of that, repeat the procedure. Maybe try a bit higher base idle, but you shouldn't go too far.

Then for something completely different... 4-cyl auto-trans cars have a vacuum-operated rear engine mount. (Down low between engine & firewall about midway side-to-side. Follow the vacuum line & find a solenoid valve. Get a helper you trust...
1 - Engine all warmed up.
2 - Car idling - shift into D & hold the brake.
3 - Unplug the wire harness from that solenoid valve.
That should make the vibration noticably worse. If not, something's wrong with the mount or with the vacuum lines or the solenoid valve.

But since it's ONLY when the engine is cold (right??) then it might be the FITV. That thing is bolted to the underside of the throttle body & it's job is to let extra air in - bypassing the throttle & raising the idle when cold. When the engine warms up it should close. Sounds like maybe when cold it doesn't open far enough? (Usually they fail the other way & let air in when warm.)

 

So I noticed today that it idles a little low and rough when warm too, but only in drive. I will check the solenoid. I already looked extensively for vacuum leaks to no avail, that doesn't mean I don't have one, I just haven't found one yet. Thanks for your help JimBlake!

 

I am having the EXACT same issues, 97, f22, manual. Can anybody put the diagrams up for both the items suggested? the FITV or whatever and the other...IAC or whatever its called?

thanks cuz the weird idle surging is kinda embarrassing and when I have the air on it drops real low but stays around 550 i believe

thanks again

 

I am going to start a new post about the motor mount, so the title on this stays more accurate

 

IACV = idle-air control valve = #19 on the back of the intake manifold.
FITV = fast-idle thermo valve = #14 underneath the throttle body.
Boost valve = #15 on the other end of the intake manifold - that might have something to do with surging idle too.