idle set, then goes back up...

[Volkspanzer]

I set the TPS voltage on my '85 to .54 and got the idle down to 700-750 in park. Driving home it went back up to 850-900 in drive. I set the voltage with the key on, does the motor need to be running also? Any ideas why the rpm's would creep back up?

 

[Jeb]

Do not set the voltage with the motor running.

You might try clearing the memory by disconnecting the battery and let the computer reset to the adjusted voltage.

 

[vetteboy86]

There are some other variables in the equation for a proper idle. The TB butterflys need to be clean. The IAC can influence idle charateristics. Also the throttle cable could effect the idle. There is a whole procedure here. Basically go through that. It might come down you actually turning the idle screw to adjust the idle once you have the TPS set.

 

[Volkspanzer]

Hello, today I broke down and started turning the idle screw. I did notice that with the volt meter connected to the tps, the voltage changes with the screw as I turn it. Does this have an affect on the setting? Like if I set the tps to .54v and then turn the idle screw will the 5.4v change or will the computer maintain that voltage? AAAARGGHH!! lol

 

[vetteboy86]

The TPS voltage will change as the throttle moves. This is how the computer knows what throttle the engine is currently at. It is just a potentiometer setup. However what you do know is not exactly clear to me. There is a procedure to follow. Now that you have turned the idle screw you need to reset the TPS.

 

[Volkspanzer]

So after turning the screw after having already set the tps to .54 I need to reset the tps to .54? If there is simething else I'm missing please let me know.

 

[redvett]

So after turning the screw after having already set the tps to .54 I need to reset the tps to .54? If there is simething else I'm missing please let me know.

Yes having owned an 85 that i drag raced i know a lot about 85's. Check your timing first of all no more than 2-3 deg advanced over specs. if you have a vaccume leak its going to idle faster. Check the IAC counts to specs. EGR leak will cause high idle. To check plentum leaks get engine up to operating temp and put hand over mas air flow sensor and starve engine of air, if the is a leak in the runner gaskets it will have a high pitched squeal.