Jeep Renix Gurus..TPS adjustment not responding

John Fuller

John Fuller

XJ Fanatic!!
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Jan 3, 2015
Location
Boone NC
my 88 XJ 4.0 auto Renix: last few weeks started doing the high idle when you first start it then falls to normal and runs fine but everytime you crank, idles high then lowers. I adjusted the TPS like usual....
4.92 volts signal coming in and I AM able to adjust it to .8 volts output but no change in the idle issue...the sensor has been replaced by previous owner at some point within last few years as i can tell. Everything on the jeep is NEW except Computer and Map Sensor, all other sensors/engine components are new and runs great other than this now.
---anyone know of any other way to test TPS beside the voltage procedure to know if it's good or bad before i go buy one? i haven't personally run across other sensors causing this issue of high idle at start-up but figured i'd ask if anyone has. thanks for advise jeep guys
 
yeah its new...i swapped it with 2 others just to make sure and no change so new one is back on
 
Not positive on this for Renix, but on some obd1 stuff, you can have the ecu relearn a new idle position by manually setting an idle speed with the throttle stop and the iac unplugged.

You set the desired speed, shut engine off, plug it back in, put the throttle stop back where it should be, and then the computer learns the new iac location for idle.

Not sure the exact steps needed to do this on a renix system, google will help that.

Vacuum leak(s)?

Have you messed with the timing?
 
Typically most efi will high idle at start and then fall to normal.

Re-read your original post, why do you think something is wrong with tps?

Are you opening the throttle when ou turn the key on to start? This changes how the ecu sees the how the tps is adjusted for closed throttle.

Does the idle fall to normal rpm?

Does the tps have a smooth voltage curve?

Nothing more to a tps than a variable voltage regulator...

Is the problem you are trying to fix only fast idle at initial start up?
 
yes it drops to normal about 15-20seconds after startup and when i say high idle, i mean the 2500-2800 kinda high idle...not normal.
TPS is 98% of the cause on these jeeps for high idle when they do this at startup on these Renix Ignition systems but i've never seen one test good on voltage but cause high idle issue on start-up is the main point i am trying to fix.
 
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