RPMs Sticking **HELP**

[Mich88XJ]

I have had a problem recently with my RPMs not dropping down to idle speed after driving for about 3 miles. It only does it sometimes, but it sucks because I have to hold the brakes while the torque converter is still locked up. If I drop it in neutral, they jump to 3000 RPMs but in drive they are about 1200-1500 RPMs. My manual didnt say much about this other than to check the throttle linkage and the choke. I did, but it still does it. If I shut off the car and start it about 3-5 times, it finally stops. Any ideas would be helpful.

 

[89xj]

what year and engine???

fuel injection-
sounds like the tps. disconnect it from the wiring harness, clean the connection with electrical contact cleaner and reconnect.

or is carburated, you mentioned the choke?

 

[JEFF]

Could be the AIS motor on the T-Body, my 87 XJ did the same thing. I tryed cleaning the throtle body and this fixed it for a little while but it started all over again until I replaced the AIS motor

 

[Mich88XJ]

Okay, yesterday it started idling really low, to the point where it would sputter for a split second before it took off, and sometimes even die. Would it cause this also? By the way, I noticed you live in brighton, and I live in Algonac (on the tip across lake St. Clair from macomb county). Do you know of any wheeling clubs around here.

 

[Mich88XJ]

Oh yeah, it is a 4.0L fuel injected.

 

[88 Jeeper]

clean your Idle stepper motor on the throttle body, carefully. try not to touch the pintle. then clean the wiring connectors to the ISM and the throttle position sensor. sounds like you have a defective throttle position sensor.. even tho you are trying to idle, its telling the computer and tranny that you are trying to rev at 3000 rpm or so. if you have a voltmeter you can check its spec's, just do a "TPS adjust" search or something similar and you should find what you need, or in the FSM if you have it. idle motors are ~60 from non dealer places, and TPS's are about 80-90 for non dealer. at 20+ for mopar sensors. keep throttle body cleaner away from the TPS sensor, it doesnt like that stuff.

good luck

 

[PaulJ]

What year? The early Renix ones have the evil C101 connector near the brake booster. This connector can cause the problem you are seeing.

 

[Mich88XJ]

It is an 1988.

 

[Mich88XJ]

I just went to check my TPS today following the directions in the Haynes manual, it shows a 3 wire harness, and yet, mine has 2 separate 3 wire connectors that run to the TPS for a total of six. I don't know which wires to use to check this. It also said to back probe the electrical connector (what do they mean) and "don't unplug the connector from the TPS." Can someone please tell me the wires that I need to use. Thanks!

 

[satan]

Similar thread - with data on connectors and pins... http://www.naxja.org/forum/showthread.php?s=&threadid=3378

"Back Probing" indicates that you measure the voltages with the connectors still attached - yu can sneak a "probe" tip into the "back" of the connectors with very little effort

 

[Mich88XJ]

Hey, thank you for that link, it explained everything I needed to know. I don't know why the book didn't describe this. Anyhow, I am going to try it tomorrow when I get home from school. I will let you know if it worked or not.