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STS misfire, spark plug question


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I have a 1995 STS 4.6L. It´s having a misfire when passing 80km/h (55mph). It´s just a few coughs, then it´s just fine again. Could it be spark plugs or wires? Someone told me that it has special plugs that should hold up for 160000km (100K miles). Is that for real? I´ve never heard about anything like that before. Unfortunatly, cadillac is a very expencive brand of car here in Norway, so the local car repair shops don´t have any experience with this motors. Can someone tell me?

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You can expect the factory installed plugs (ACDelco) to run to 100,000 miles. The main difference in your "special" plugs is the use of platinum electrodes but that is a significant difference in terms of plug life. For more than you wanted to know about platinum plugs, here is just an example of what is available on the web. http://www.babcox.com/editorial/cm/cm120032.htm

Your misfire could be caused by a number of things including plugs, plug wires, wire routing, and coils. According to your description, a fuel system problem seems unlikely. You will have to systematically eliminate possibilities. And a competent repair shop should have no difficulty diagnosing an ignition problem on your engine since all gasoline engine ignition systems do exactly the same thing.

I experienced a problem similar to what you describe on another engine type. The problem turned out to be one of the ignition coils was failing under certain conditions. Difficult to diagnose. Satisfying to repair.


Drive your car.

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Can you order the parts online, and ship to your home, as time is not urgent.

Alos, run thru the diagnostic check looking for codes....

A hickup if only once or twice, and no other problems, have you considered a fuel "quality" problem - water, dirty injector?

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Platinum tipped plugs will last for 100,000 miles but they will be pretty well worn by then - I'd suggest new plugs, then new wires.

I bought my high performance wires here: http://www.ultrarev.com/home.php but you can probably get them cheaper elsewhere. ;)


1996 El Dorado

2006 STS

2000 Corvette

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