Originally Posted by investinwaffles

I honestly would have gapped them to be doubly sure (especially when trouble shooting). Fitting size wise is totally different than what the spark plug gap dictates, but as long as they all looked to be the same gap it should run pretty well. The parts store guy mostly just wants to ring you up and doesn't give a rats a$$ about what they are gapped at though, so dont trust them too heavily.

As for tightness, like I said - tighten them till they are snugged up to the block and then tighten another half turn (I believe the champion's have that written on the box as well).
For reference, 15 ft-lbs is not very tight (your lugnuts should be torqued to 100 ft-lbs, which is tight as *****). The spark plugs wont break if you overtighten them, but the threads within the head will strip which is infinitely more of a PITA to rectify.

Coolant, look in the overflow reservoir to make sure its bright green and clean, and do the same under the radiator cap when the engine is cool enough to open it. Brownish or with particulate floating around -- flushing it would probably be advised.

EDIT:
And if the radiator is original, DO NOT TOUCH THE DRAIN PLUG. You will crack it by even looking at it and I ended up replacing my radiator (doh!). Unhooking the lower coolant hose is the easiest and cleanest way to drain the system. Flush it out thoroughly with the hose, and buy several gallons of distilled water. After the water from the hose comes out clear, fill it up with distilled water and let it get to temp (blower + heat set to high). Drain + fill twice with distilled (or until it comes out clear), then refill the system with antifreeze mix.

DOUBLE EDIT:
Also try to reset the PCM/ECU and reset the engine parameters to factory. Might help with the rough running if you haven't tried it yet.
http://www.quadratec.com/jeep_knowle...article-89.htm



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