Fast Idle - No Shift - 90 4.0

[melwade]

I just replaced my engine. Runs great now, but the idle stays at 2200 rpms and the transmission won't shift. I'm leaning toward a vacuum leak - however i've replaced most of the vacuum hoses. Here are some of the other accessories I replaced in the process:

• Alternator - now 120 amp
• Engine/Firewall ground strap - old one broken
• New CPS

I read most of the idle thread but didn't find anything that fit this directly...

 

[birchlakeXJ]

For high idle, a vacuum leak is most suspect. Have you tried spraying a light mist of water or carb spray around all components to see if it changes the idle at all? You could also try cleaning the idle air control, another suspect for idle quality issues.

For your tranny problem, does it not shift from park to 1, or doesn't shift from 1-2?

 

[JoesXJ]

TPS? When mine went out, my r's where high and tranny wouldn't shift.

 

[lawsoncl]

Yeah, TPS is the first thing to suspect for odd or unusual shifting. It can also cause your high idle.

 

[melwade]

Interesting thing... I went to start in this morning after being out in the cold all night and the idle was fine. But the Transmission still won't shift. I can go up to 25 mph. I think it stays in 2nd - but I'm not sure on that one.

 

[birchlakeXJ]

As the TPS is responsible for certain shifting issues, I would definitely take the time to confirm it. Your vintage (1990) I'm quite certain is ADJUSTABLE. I'd be sure it is in spec.

 

[melwade]

I've never figured out what caused the fast idle but I did track down the shifting problem. There's a wire on the transmission that I disconnected and forgot to reconnect... Classic "ID ten T" error. :laugh:

 

[xj88superjeep]

Double check for vacuum leaks if you solved the shifting problem and still have high idle...

 

[melwade]

Thanks. The fast idle hasn't returned since the first day...

 

[mcnamaag]

So did you ever check the TPS? It does controll idle AND trans shifts.