: 95 Deville Concours 4.6 bucking while in gear and AC compressor on

06-27-10, 01:27 PM
I just changed sparkplugs, ISC motor and now the car bucks wildly while in gear and the AC compressor is on. If I turn the AC off, it stops. I'm not sure what to do, any and all help would be greatly appreciated.

06-27-10, 01:45 PM
Did you also remove and clean the 4 coils and their base contacts as well as the ICM and ICM ground lead ?? Are all the plug wires connected as shown ?

1995 - Are the plug wires new ??

06-27-10, 08:43 PM
No, I didnt change plug wires, they are all hooked right, maybe just need new ones. Why would it only do it when the AC is on?

06-27-10, 10:08 PM
After the fuel rail recall, my '97 had a misfire. Wires looked fine, but a new set cured it. A/C puts a load on the engine. Does it also mis on light acceleration?

06-27-10, 10:53 PM
Thanks, I cleaned the terminals on the ICM and all seems fine, for now. I will replace spark plug wires next just because they are old. They test fine but will change just for preventative maintenance. Thanks Alot!!

06-28-10, 11:40 AM
A/C Delco wires are expensive. If it ain't broke, don't fix it.

06-29-10, 12:49 AM
Ranger I was reading your post , where you asked if "...it also mis on light acceleration.." .I have asked this question several times over the last year or so, about this phenomena, cuz I have the same experience. Actually it feels like a slight hesitation, when its under any load, like going up a slight incline, it hesitates, so I drop it down into 3rd to build up rpm's and it smoothes out. Sorry I am referring to my 94 Concours, 4.6L. But I have to keep the rpm's up I don't get any codes, but it is irritating. Any thoughts?.... BTW I love my car, and plan on keeping it, it has about 101K miles. If it's the plug wires, can they be checked before replacing them? I ask because when I bought the car I had a mechanic check and repair any/all problems, and replacement of the wires was one of the issues. That was at about 85K miles which was maybe 2 years ago.

06-29-10, 09:38 AM
If you have resistance meter, you can check the ohms on the plug wires.

06-29-10, 12:15 PM
If you read the thread that I linked you in your PM, I believe that I checked my wires and they Ohm'd out OK, but in the end they where the cause of my misfire.