I have been trying to track down a rough idle cause for so long now. While I was at the junkyard last week I noticed that all the coil packs in the xjs were black. The one on mine is a dark blue. I was wondering if anyone else has a dark blue coil pack thats factory. Im thinking maybe the PO put an aftermarket one thats going out on me and causing my rough idle? I have a 2000 4.0. Just curious if anyone else has this blue coil pack. Thanks.

 

I have one from Napa that's a kind of dark blue. Have you done a full tune up? Vacuum leak? Fuel system cleaning? IAC clean? TPS, CPS checked?

 

Ive checked for vacuum leaks and found none. Tested every sensor but the cps. I didnt know you could test that one.

 

Wrong thread my fault