Which NGK Iridium spark plug would be the best for my 2001 Jeep Grand Cherokee with the 4.0 enigine?

RIZ

 

I'm running ZFR5Ns in my 2000. No fouling or misfires with 192K on the engine.

 

Awesome! ZFR5Ns are the ones I was looking at.... thanks for the info. I pulled the coil pack off and removed all 6 plugs, going to replace them with the NGKs and go from there. .... do they come gapped correctly already? If not, what should I gap them all at? .035" ??? 038" ???

RIZ

 

They are usually factory gapped for the application, but check them anyhow. 0.035 is the proper gap, but they could have been rough handled in shipping. I had a Champ with a cracked insulator that I didn't catch until it misfired.

 

wow, I'll check them over good. About to run out and get the plugs, spark plug gapper and anti seize. I'm hoping it isn't the coil pack but if it is, it's easy to fix.

RIZ

 

You really don't need the antiseize. The threads are plated to prevent seizing.