Originally Posted by klong31
2005 JGC w/ 112,000 miles
Started it this morning and was surprised with a check engine light! Scanned for codes, P0304. - My 22 mile drive into work was fine, no rough idle or harsh driving on the hwy.
Brief History of latest maintenance;
-Tune up @ 95k (new plugs, fuel induction, trans flush)
-New Control Mod and Ignition switch @ 105k (Thanks, remote starter for frying my wires and system)
-Water pump @ 107k
The jeep is running fine, no noticeable loss of power.
Did you/they check the ignition wires when the tune up was performed? I would check the resistance in those first.
A P0304 is a misfire in cylinder 4, so the usual culprits (coil, plug, etc.) would be the next thing to check. What type of plugs were put in during the tune-up?
On the more rare, but still possible side you're looking at EGR valve (which are known to go around your mileage), vacuum leak, crankshaft/camshaft position sensors. Usually all of these would be accompanied by stalling or nearly stalling behavior.