'89 Cherokee

I have this one problem....when gettin ready to start it up stays at normal idleling point needle raises to 1000rpms/500rpms then shuts off automatically!.....

That sounds like a IAC issue and it may need to be cleaned. The Idle Air Control is the round can looking thing on the front of the throttle body nearest the engine. Remove the 2 screws and pull it out and take a look(make sure the engine is off, don't try to start it with the IAC out)it is probably dirty and is sticking.

X2 clean the IAC with some break clean then wee what you have.

Although you two may be right about the IAC, the fact that idle increases and decreases before the engine turns off tells me the IAC is working, but that something else is giving the computer bad data, like a poor or loose, variable resistance ground on a sensor or on the entire engine, or a funky air or coolant temperature sensor, or problems with the TPS or its ground. Renix engines are notorious for variable idle speeds being caused by poor ground connections. Not just one ground wire, but all of them!

Does it die if you hold the throttle down to say 1500 rpm while it warms up? Does it die after start up only when it is cold, hot or all the time?

as with most renix issues.

1-measure resistance at grounds, clean them and/or replace them.

2-verify all your harness plugs for sensors are not corroded, if so clean them up with a small file and/or pick, TPS, CPS, IAC, IAT, CTS, etc etc etc.

Thanks, I appreciate all of the naxja guys!

Not when its cold, Dies when its hot occasionally....
I changed the TPS/CPS.

Ecomike said:

Although you two may be right about the IAC, the fact that idle increases and decreases before the engine turns off tells me the IAC is working, but that something else is giving the computer bad data, like a poor or loose, variable resistance ground on a sensor or on the entire engine, or a funky air or coolant temperature sensor, or problems with the TPS or its ground. Renix engines are notorious for variable idle speeds being caused by poor ground connections. Not just one ground wire, but all of them!

Does it die if you hold the throttle down to say 1500 rpm while it warms up? Does it die after start up only when it is cold, hot or all the time?

Click to expand...

What kind of stuff?...... can i use to clean up my IAC?
Do i have to be careful pulling the IAC of my throttle body.
I think theres a spring thing.....attached to it. Right?

Just unplug it and remove the 2 screws and pull it out. There is a sealing "O" ring around the base, try not to bugger that up and use some vaseline on it when you put it back in. It helps seal vacuume and with it you will get some funny idle issues if it is not sealed good.

I use either brake cleaner or electric cleaner on the pintle end only, not on the motor or can. Put a drop of light oil near the back side of the pintle near the motor when the clean up is done. You should take this opertunity to clean up the TB really good as well. The area the IAC goes into will be very dirty!

xjtrailrider said:

Just unplug it and remove the 2 screws and pull it out. There is a sealing "O" ring around the base, try not to bugger that up and use some vaseline on it when you put it back in. It helps seal vacuume and with it you will get some funny idle issues if it is not sealed good.

I use either brake cleaner or electric cleaner on the pintle end only, not on the motor or can. Put a drop of light oil near the back side of the pintle near the motor when the clean up is done. You should take this opertunity to clean up the TB really good as well. The area the IAC goes into will be very dirty!

Click to expand...

Words of wisdom above on how not to screw up the IAC!

If the IAC and idle are acting OK at cold start up and idle is normal at cold start up, I would suspect the IAC is OK, and maybe the intake air temperature (IAT) sensor is stuck reading out a cold fixed temperature (resistance no longer varies with air intake temperature?) or maybe the coolant temp sensor is bad. Or once again, as I had for 2 years before I finally fixed all my grounds, it could be thermal variations changing the reference ground resitance in the Renix computer sensors. If the ground is loose and dirty, heat and vibration can change the ground contact resistance making the computer think some sensor positons have changed.

You can test the ground wires (all should read less 1 ohm to the battery post ground with power off), and sensor grounds and temperature sensors with a simple ohm meter. The correct temperature sensor readings at different temperatures are posted in several threads here.