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cruise control not working as it should

1K views 8 replies 4 participants last post by  v8nick 
#1 ·
Over the weekend I replaced the heater core in my car, now the cruise isn't working as it should. If you set the cruise, it immediately speeds up about 5 miles an hour faster than where I set it and then it will slow down and speed back up, repeatedly. I have looked at everything and all I can come up with is either there is a vaccuum leak or the amplifier is crapping out. Any thoughts on this?
 
#2 ·
I thought these cars used an electric servo on the cruise control instead of the older vacuum controlled? I'm not positive, but I'm pretty sure.

However, a vac leak could still cause the surging. Also, I had a TPS not functioning correctly on my Mark VIII that caused that kind of behavior though not quite as drastic as what you're describing!
 
#8 ·
Yah, the 1991 at least sucks ... :diablo:

RwP
 
#4 ·
It's under the driver's side fender - have to pull out the plastic wheel well to get it. I already sold the one off my parts car...
 
#9 ·
I got it figured out. I checked and rechecked all of the vaccuum lines, and nothing. That led me to recheck the amplifier box under the hvac housing. There was one wire that had gotten pulled out of the harness connector that I hadn't seen. I pushed that back in, and the cruise works.
 
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