QuestionQUESTION: I have a high speed misfire that has thrown a code at 68 miles perhour 3 time. Exactly at 68mph 3 X ?
Replaced, cat. conv's, dist. cap. plugs, wires and coil. Chev dealer replaced the fuel injection system. Same problem, now dealer says sticky valves, need valve job. Put Sea Foam de-slugger into oil, no difference. 150k, but very well maintained.
Oil in really clean.
ANSWER: I would be interested in knowing if it is only one cylinder misfiring or if all are misfiring. If it is only one cylinder, it could be a valve, or an injector. If it is all cylinders it could be a cam position sensor or something similar. See if you can find that information out.
Hope this helps
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QUESTION: Thank you for your time with problem, it has been very trying.
It is multiply cylinder misfires with number 6 cylinder being the most or highest number.
AnswerHmmm. I would be doing two things I think. The first is I would be asking the dealer why they have put all those parts on it if none have fixed the problem. Shouldn't have to pay the full bill I wouldn't think. Ask them if they have checked service bulletins or contacted the technical assistance line for advice. Both are excellent resources when you have a problem that you cannot figure out. I would recommend looking at the cmp position reading at cruise, if excessive it can cause 'fish bite' or surging and misfiring at hiway speeds. Aside from that, I would have the dealer take a snap shot using their scanner and send it to the TAC (technical assistance centre) I would also not pay another dime until the problem you wanted fixed the first time is fixed properly.
Hope this helps
