cruise control won't hold

[kirkwood]

lot of great cruise tips here, but can't find my specific problem.

Wehn driving at highway speeds, if i click the set button it will grab, but won't hold as soon as I let go of the button. If i hold button it will continue to accelrate.

I have checked all wires for continuity/reistance per the TSM, and and the vac canister holds great vacuum. I put a new servo on it even!

The engine/electronics are from a 93 XJ, but it is a 4.0 swap. I have a TF transmission, so I used a speed sensor from an aftermarket company. They tell me that the speed sensor is totally compatible with the Jeep PCM, but this problem points back to it.

The speed sensor I have puts out out a 8PPR square wave signal, supposed to be around 5-6 volts DC output. Does anyone know what the factory sensor is supposed to put out? I can't find a spec for it. Of course, if anyone has any other ideas I'd apreciate your input!

Thanks!

 

[rocklandxjer]

check for vacuum leaks elsewhere in the engine. could be a small leak somewhere else besides the canister

 

[jneary]

possibly the plastic lines under the battery are corroded

 

[kirkwood]

thanks guys.


the line rus from the intake to the canister to the servo, lines are new and I have tested the check valve/tank with a vac tester and a guage - looks like vacuum is not the problem.

 

[jneary]

may be the check valve in the vacuum line near the intake port. it might not be holding vacuum

 

[heyhar]

I have a '92, and have had the same problem intermittantly for the seven years I've owned it. Recently, I purchased the new stalk/switch from Jeepsareus.com, and it now works more often(!). (The washer paddle was broken, so now that works, too). What I have come to notice is that it almost always will not work if the headlights are on. On a warm sunny day, push the button, and it grabs good. Gloomy, or at night, with lights on, it will barely grab, and quickly peters out. I have been wondering if the Neutral Safety Switch plays a part. Sometimes, my reverse lights don't work, either. And, the cruise might only want to work if the car was in gear? Just a thought.