I have 1997 XJ and I just bought NGK ZFR5N plugs. My XJ calls for 0.040" gap but the plugs I bought come with a 0.036" gap. Should I leave the gap at 0.036" or go up to 0.040"?

Thanx!

 

Gap them according to the factory specs. Spark plugs are not always gapped correctly out of the box. That .036-.040 might not make much difference, but i always gap to whatever the factory says to.

I believe the proper NGK plug for 97 is FR5-1. But whatever works for your vehicle. Some dont mind. My 97 uses Champion RC12LYC, gapped to .040.

Scratch that. Found my notes for its last tuneup and the plugs were gapped to .035, not .040. The OLD plugs (Bosch) were .040.

 

Ok I guess I’ll try them at 0.036”.
thanks.

 

 

he told you to gap them to factory spec? Thats what I would do

 

The NGKs are recommended for the 00-01 engines with the waste spark system. Yours is supposed to take Champions. AFAIK it really doesn't much matter.

 

RC12LYC .035 gap This is out of my 95 but a 97 was my last XJ and I could have swore it was the same up until the move to Coil Packs with the waste spark. I had a 00 but can't remember the specs on that one.

 

Scratch that. I still have my 97 FSM stored. Here's a screenshot straight from the 97 factory service manual. It (the FSM) also covered up to the coil pack Jeeps. If you still have your original manual you can check in there as well or the sticker on the firewall should also have the info.

 

thanks

 

Just for an update I did install the NGK ZFR5N plugs with factory gap (0.035'') and the engine seems to be running better than I can ever remember.
Thanks for the help.

 

nevermind