Input Needed For TPS/High Idle

[mjfrancesca]

I hate to ask but I wanna ensure I don't really mess anything up.

 

1989 4.0 Manual.

 

I have the high idle issue, where I start up and after five or so minutes my rpms climb upwards of 2500. But if I drive it around the block and let it sit, she idles fine.

 

I have replaced/cleaned all grounds, cleaned my throttle body, replaced my IAC. I've been talking with Cruiser but I know he's always being swamped with other questions so I try not to bug him.

 

 When I try prodding my wires for readings, AB I do get 4.9 volts but my BC I get a 4.62, which seems low. Should I get a new male connector and try readings again? I have a replacement TPS (and I don't mind throwing money to update the vitals considering everything was pretty nasty in the bay) I just don't know whether to replace it blind with potentially botched readings or if someone knows a baseline number I should aim for.

 

hopefully this all made sense I appreciate the help as always.

[87MJTIM]

I guess you are taking the readings from the square terminal, not the flat terminal.

 

Have you adjusted the TPS?  The 4.62 is high.  The BC output should be .83 of the AB output.

 

A high idle like you describe could be vacuum related.  Have you checked the vac line from the MAP to the throttle body?

 

I have recently had trouble with the TB not closing all the way when I release the pedal.  It only rev's about 1000-1200, thou.  Look to see if the TB is stuck initially.

[mjfrancesca]

Thanks for the response,

The manuals only have the flat three plug which is where I'm getting my readings.

I haven't adjusted anything to avoid messing something up, I noticed my readings weren't in the ballpark and just kinda got spooked.

 

My apologies, CORRECTED READINGS

AB: 4.92

BC: .52

AC: 4.35

 

I kinda had my notes botched up.

 

But I did end up replacing that hose and threading it with the brass fittings etc like on the cruiser tips since previous hose ended up cracking with fuel injector install.

[Ωhm]

Loosen TPS mounting screws and set BC=0.85vdc. ECU will need time to relearn Closed Throttle voltage. Drive it.

[mjfrancesca]

31 minutes ago, Ωhm said:

Loosen TPS mounting screws and set BC=0.85vdc. ECU will need time to relearn Closed Throttle voltage. Drive it.

Perfect thank you! Now do you think this is a culprit of some sort? Not sure what the effects would be with my readings be so off. Sorry for lack of knowledge just want to learn :)

[Ωhm]

TPS is a major component for fuel delivery. Normally when BC reading is set higher then 0.83vdc, I just noticed I previously posted 0.85vdc WRONG set to 0.83vdc, engine will have high idle, but maybe too low of a reading will cause the same issue.

[mjfrancesca]

Wonderful I appreciate it more than you know. I figured it was something fuel, I was worried it was the 746 injectors or something. I'll get to adjusting tomorrow and hopefully it helps 

[87MJTIM]

Here is the Renix fuel injection manual.  It's a great reference source for our Renix Jeeps.