Cruise Control

89 4.0 XJ. Cruise previously didn't work, replaced switch and still doesn't work. The acceleration feature of the cruise works, just won't hold the speed. Now is this due to the common wire problem or could this be due to a leak in the vacuum, considering the accel works. I just don't know how the accel. function is used (electrical vs. vacuum or both), to rule out the electrical or the vacuum.

Thanks,

K

Check for vac. leaks at the little "blimp" vacuum canister behind the bumper. Both my cherokee and my brother's comanche had the same problem, leaky vac. canister. The cruise would set and work for maybe 2 miles, then just die. goobered up the vacuum line connections at the canister to seal any leaks and all is good, no more sketchy cruise.

Well I understand how the cruise works. Mine just won't engage to keep the specified MPH. It doesn't "die off," if just doesn't work. My only problem is that the acceleration part of the cruise control works, while the actual cruise doesn't. So does this pinpoint the problem being the vacuum, even though the accel feature works, or is this due to the common wires going out in the stalk? Basically, what does the acceleration function of the cruise control use, the vacuum or does it work via electronics only, so that I can rule out one.

K

I seem to recall the accel using vacuum, but it's probably just engine vac that's accelerating you; will it hold an acceleration for a wide range, say 55-70? In addition to checking the vacuum bottle, look carefully at the lines as they progress back into the engine compartment, especially under the battery. That area tends to get leaks pretty readily.

kellen said:

89 4.0 XJ. Cruise previously didn't work, replaced switch and still doesn't work. The acceleration feature of the cruise works, just won't hold the speed. Now is this due to the common wire problem or could this be due to a leak in the vacuum, considering the accel works. I just don't know how the accel. function is used (electrical vs. vacuum or both), to rule out the electrical or the vacuum.

Thanks,

K

Click to expand...

check for broken wires at the brale light switch. also there is a vacuum switch on the top of the brake pedal. make sure the pintle is puhed in when the brake pedal is fully up.

I have the EXACT same problem you described with my 87. I made a post a few weeks ago asking about it, just haven't had a chance to follow up on it... to many other projects going on. Good luck!