1999 jeep xj sport rough idle even with tune up
 

Hi I'm new to the site and have a few problems with my xj. On start up my jeep shakes and the rpms shake between 50 and 100 I occasionally get a cylinder 3 misfire . I have replaced the spark plugs and wires and the problem continues. is it a possible bad injector or a head gasket leak. No milky oil and once driving the car runs fine. I'm stumped can anyone help?

What spark plugs did you put in it?

Did this happen BEFORE you replaced the plugs and wires or AFTER?

1999 runs best on Champion RC12ECC or NGK ZFR5N, by the way. You couldn't convince me to run anything other than OE coppers in a stock 4.0L.

Are you getting any other codes than P0303?

Before can't remember what kind some sort of copper I think I just ran some sea foam and it runs a lot better might have solved the problem

They were auto lights similar to the stock gaped at .35

If the problems continue do you have any other ideas

Switch out the plugs for those champions or NGK's and work from there.

Yea I will Try it out thx for the advise

when i first picked mine up a few weeks ago it was running the same..(was throwing a 306 and 206)
swapped the plugs and wires and i figured for the few extra $ i'd do the cap n rotor at the same time....
runs beauty now