MUKAK

for the last few months i get this occasional problem when i start my 89 Renix it jumps to 3000rpm, i turn off the car and start again and it idles normal

today after a car wash i start the jeep and it goes up to 3000 and no matter what i do it stays there.. had to drive 20 miles home in traffic like this

i had the same problem 2 years ago and i replaced a few sensors ( cps, and the 2 sensors that plug to the Throttle body ( forgot what they called ) and it was driving perfect since

which sensor needs to be replaced? i allready checked throttle linkage and its fine

67 GMC

On the throttle body, one is the TPS (Throttle Position Sensor) and the other is not a sensor but the Idle Air Control. There are lots of tips on here on how to check the TPS. If you change it, you still need to do the adjustment so read Cruiser's tips on that.

Big David

My guess is the TPS. Tap on it & I bet it will idle down.

GregGA

Cruiser54 is THE man. You want to read his tips on Renix Jeeps. I would link you if I knew how, but I am new to this forum, but I have known him for years on another forum. He is the reason my Jeep runs like a scalded cat.

On my 87, I too had a high idle. Following Cruiser54's tips I refreshed all grounds, then adjusted the TPS. Problem solved. Only buy your sensors, if needed at the dealer, or possibly NAPA. They are too critical to use "lifetime'" warranty crap.

Cruiser will respond to this this thread, I'm sure!

'90Cherokee

Almost definitely not the TPS, it's the Idle control valve, been there twice on mine now. If you get it to idle normally again while warm you can disconnect it to at least have a usable idle 'till you get it replaced, it won't compensate for a cold engine and will idle low 'till it warms up--been there when mine died on a trip. If you disconnect it during normal cold idle it'll idle high warmed up, but not 3000 like they like to do when they fail.

jeepfreak82

Could be MAP sensor also, seen this happen in a friends same year also

cruiser54

Very likely the TPS is going bad on the Engine side.

Clean the throttle body and IAC-Tip 11, and try adjusting the TPS per Tip 8.

If you've never done the ground and connector refreshing, now it the time to do so.