High Idle When Hot

Vacuum leak.

See the sticky "Help me create the Surging Idle Checklist" at the top of the forum for help with your idle problems. The first most contains all the updates to the fixes. I continue to update it as more people post fixes or ask questions.

Do you know how the TPS is doing?

Its the IAC ive had this problem with my car for years. The only way I could fix it was by taking off the IAC and making the holes smaller by fabricating a small aluminum piece so less air gets by. This allows me to have much more control with my idle screw.. Yes its a redneck way of doing things but oh well!!

did you check tps voltage?

GearHd6 said:

The voltage actually seemed to work backwards, it has more volts in idle position and when I increase the throttle the voltage goes down. Then I put another known good TPS on and it ran and idled exactly the same.

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How are the 3 TPS wires testing with your meter? That certainly seems like an issue that needs addressing (to me). The inverse-function TPS's dont work as well as the conventional versions.

Good luck.

I would test each wire (Vref, TPS ground, etc) individually and note the values.

Good luck.

GearHd6 said:

I used the orange and the green wire to do the testing. I set my digital meter on the 20 volt setting and it showed about 4.5 volts at idle.

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You used the wrong wires.

orange - 5 volt reference from the computer
green - TPS signal output
black/white - TPS signal ground

Use the black/white wire for ground and the green wire for the TPS signal.

Try this... Currently there is some dispute about setting it at .99 volts being worth the effort, but anything less is probably OK. All you need is less than 1.0 volt at idle and more than 4.25 at Wide Open Throttle (WOT). You'll need a Digital Voltmeter (DVM) to do the job.

Here’s a TPS tip I got from NoGo50

When you installed the sensor make sure you place it on the peg right and then tighten it down properly. Loosen the back screw a tiny bit so the sensor can pivot and loosen the front screw enough so you can move it just a little in very small increments. I wouldn’t try to adjust it using marks. Set it at .97v-.99v, the closer to .99v the better.

(copied from MustangMax, Glendale AZ)

1. Always adjust the TPS and Idle with the engine at operating temp. Dive it around for a bit if you can and get it nice and warm.

2. When you probe the leads of the TPS, do not use an engine ground, put the ground probe into the lead of the TPS. You should be connecting both meter probes to the TPS and not one to the TPS and the other to ground.

3. Always reset the computer whenever you adjust the TPS or clean/change any sensors. I just pull the battery lead for 10 minutes.

4. Check the procedure for your year, on my 90 I have to turn the idle screw until it just touches the tab, then insert a .010 feeler gauge and give it about one more turn. Then you adjust the TPS voltage to .98v, reset the computer. Start it up, if the idle is to low then turn the screw in until it is just right, then readjust the TPS voltage to .98v and reset the computer and start it up. The key is to adjust the TPS voltage and reset the computer whenever the idle screw is changed.