My 1995 XJ6 has a lot of miles on it, but has been taken care of well over its lifetime (I am 2nd owner). This is my first winter with it and suddenly on the first really cold day (10 degrees F) it is running roughly, like it's missing.

I put a bottle of fuel injector cleaner in with the last fill up, but I'm not certain that helped.

I have never owned a car with coil packs. Is it common that cold weather will cause a coil pack to loosen?

Is it any trouble to reseat the coil packs, or does this involve installing new gaskets?

What else might I check?

 

Remove the cover over the coil packs and start the engine in the dark. If any coil packs are shorting you should see the arcing under the plastic cap.

 

Thanks, RJ237, for the suggestion.

I did as you said and did not see any arcing.

I would like to remove the coil pack wiring harnesses one at a time to see if there's a particular cylinder not firing.

Two questions:

1. How do you get the wiring harness off? Some gentle prying with a screwdriver (even two screwdrivers, one to lift the clip) didn't seem to do it.

2. Can I do this without shutting the engine off each time (will I get shocked)?

Thanks again for your help.

 

Do not remove the harness from the coils. Just pry up the little clips that hold the harness to the head. Then you can pull the coil packs off the plugs. Try not to break the paper gaskets. You can check them with the engine running.

 

I took this to a mechanic who replaced the coil pack on cylinder #1 and it runs great now!