QuestionMy mechanic has replaced wires,done compression ck and numerous diognostic tests, clears codes,car runs fine for awhile and then slips back into missfire codes. what else can he check?
AnswerHi Steve,
The manual gives the following possibilities, in addition to the wires which were replaced:
fuel pump or filter (unlikely as regards the filter), injector harness connectors, ignition coil circuit, spark plug, mechanical problem (but compression test would probably have shown that), contaminated fuel, water in fuel. pcm power ground connections, injectors, restricted exhaust, intake restriction, the pcm itself, the evap emission control system, the exhaust gas recirc valve system (this is something I would certainly recommend that he check, as if the valve sticks ajar it will definitely cause misfiring. So suggest that he lube the valve stem with WD-40 and move it back and forth with the tip of a screwdriver in the slot to be sure it is moving to a dead-stop via internal spring-action), air gap at high rpm's, other mechanical (?), and damaged trigger wheel (something to do with one of the engine postion sensor (?)). The parenthetical items are my remarks.
Many of these also might set a separate code so he might not need to concern himself with them. But the egr valve would be high on my list.
Let me know how this progresses, please.
Roland
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