oldsfreak Posted January 17, 2012 Report Share Posted January 17, 2012 My daily driver 98 Lumina with a 3100 has got a real nice misfire at idle. It all started one day leaving work. Out of nowhere my car felt down on performance until the RPMs came up. At that time the car took right off. I've hooked it to a GM Tech II reader and it showed something like 100k misfires on cylinder 2. Yes 100k. The other cylinders were either 0 or single digits. While the engine was idling it would keep counting the misfires and they would just scroll numbers. So fast that you couldn't read them. If I gave it some gas and raised the RPMs the misfire would slow the higher it got until about half throttle it would stop completely. I've done all the basic stuff (Plugs, wires, coils, injector chasing, etc.) . Let's skip to the advanced course. I also just did a lower intake gasket on it. 220k miles that the factory original lasted. I'd say that's pretty good. I'm thinking maybe a burnt exhaust valve or failing valve spring. It still gets 22mpg avg. carrying a cylinder at idle and low RPM. Thanks guys! Quote Link to comment Share on other sites More sharing options...
brake Posted January 17, 2012 Report Share Posted January 17, 2012 Try a compression test. Quote Link to comment Share on other sites More sharing options...
95 vert Posted January 18, 2012 Report Share Posted January 18, 2012 Check for a vacuum leak at that cylinder. Injector o ring maybe? Quote Link to comment Share on other sites More sharing options...
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