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1995 Pontiac Firebird Question: 1995 Trans am LT-1 Single cylinder steady misfire

 

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Visitor, 5.7L V8, Ronkonkoma, NY, March 14, 2010, 17:17

Hello
I've read a million stories about the bad LT-1 optispark problems and symptoms:The motor developed a 1 cylinder steady misfire, brought it to the shop: they replaced the plugs, and wires, so let's cut to the chase: I have the original 1995 optispark vented version on my 95 trans am, the motor has 96000 miles on it, never overheated, oil changed regularly, mostly highway miles, once again, the fuel filter, plugs and wires changed, the shop claims they checked the injectors and spark and all is well there, Paid 560 for parts and labor and it runs no better than before I brought it in. Before I brought in to the shop,the miss went from steady only at idle to steady at all ranges: running on 7 cylinders.It all happened within a week's time. I changed the water pump over a year ago with no problems motor ran great, and I will not say that a year later the problem of the miss was caused by that. Water damage from a leaking pump would have happened alot sooner I believe Can a bad optispark cause one cylinder to misfire steadily? There is no service engine light. Of all of the answers and problems Ive read about haven't heard this one before
Thanks for your help

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  • Answer #1

    Visitor, March 25, 2010, 19:28

    Followup to the above:
    The optispark was bad. It took about 4 weeks from start to finish to diagnose without replacing parts needlessly such as fuel pump, coils, egr valve etc. The one cylinder misfire progressed to two cylinders and then started popping thru the exhaust, brought it back to the shop, optispark replaced, engine runs mint. I inspected the old part: the rotor tip was rusted and pitted.

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