Need help with 89 Renix high idle

4.0L AW4 89 Renix.

The jeep has 110K miles on it, I service it regularly and runs great. A while back the TPS went bad and I replaced it and did the proper adjustment, I also decided to change the AIS with a new Borg Warner aftermarket unit I had. About 3-4 weeks later I started having high idle issues. The first time it felt like the throttle got stuck, when in neutral it was idling at 3700 rpm. I drove it on the highway trying to get it to release, I shut it off and started it up 3-4 times with no luck, finally after leaving it overnight the next day it started normal. However, every other day it does it again but on lower rpm (Usually around 1800-2200) and when I shut it off and restart it, it goes back to normal.
Any suggestions what I need to check or replace.

Thanks

I'm having similar problems, so I did this:

http://www.naxja.org/forum/search.php?searchid=4809388

ecomike seems to know his biz when it comes to renix, if you cannot find your answer by reading or searching, maybe try sending him a PM, or read through all of his posts...

Start here:

http://www.naxja.org/forum/showthread.php?t=1072534

Get a handle on the grounds first. Clean them ALL!!!!

Test the TPS (new or not) !!!

Look high and low for any vacuum tube, hose, or intake manifold, throttle body vacuum leaks.

Some of the sensors like the IAT sensor can also do weird stuff that causes a high idle. details here:

http://www.naxja.org/forum/showthread.php?t=905849&highlight=renx+files

Good luck!

My 89 Renix has gone through 6 TPS sensors in 2 years, they dont make them very reliable/

In the first link posted above by Mike, read the beginning where it says "IMPORTANT" and test your sensor grounds.

Have you ever performed a ground refreshing on your Jeep?

WraithKWK said:

My 89 Renix has gone through 6 TPS sensors in 2 years, they dont make them very reliable/

Click to expand...

WOW! All new ones? What brands were they, and where were they bought?

What went wrong with them?

When you are doing the ground checks, shake the harness near the end of the engine on the firewall. I had a TPS ground that was just laying in a splice crimp. Somebody forgot to crimp it closed, the bare wire was just laying in the crimp sleeve. Drove me absolutely bonkers, until I finally found it.

A good quick test is to voltage test from the ground near a sensor to the battery ground. I call it standing voltage, the ground circuit can act like a resistor.

Mike helped me eventually nail down my issues, process of elimination and perseverance. I also eventually discovered the two grounds at my TPS were crossed, the transmission TPS ground was in the ECU circuit and the TPS ECU ground were in the tranny circuit.:doh: Really shouldn't make much difference, except when you are trying to troubleshoot and end up following the wrong wire repeatedly.

Thanks for all the leads. I will do a refresh on all the grounds. I was wondering if the AIS would be the culprit?

The reason i did not go over the grounds, as I said in my initial post, the Jeep has not been tempered with, it has never been in an accident and all major components are still the original factory parts. On the other hand, I realize with age and oxidation some ground connection may not be in the best of conditions.

Perform the ground refreshing first. You are correct in asuming that the ground connections have not improved with age.

Renix has always been notorious for ground sensor problems!!!!

Ecomike said:

WOW! All new ones? What brands were they, and where were they bought?

What went wrong with them?

Click to expand...

Autozone specials with a 2 year warranty, in hinesight I prolly should have refreshed my grounds, seems like an odd thing for a wrench to forget to do!

Those grounds were an issue when these Jeeps were new FWIW.The refreshing should be done on every Renix Jeep at least once in it's life. Now's the time.

Those grounds were an issue when these Jeeps were new FWIW.The refreshing should be done on every Renix Jeep at least once in it's life. Now's the time.