Hello all. I have the most unusual problem with my 1994 Park Avenue Ultra. It has developed a random misfire that mechanics have not been able to trace. It had new plugs, wires, fuel filter, supercharger bearings, TPS sensor, and MAF sensor replaced when I bought it 4 months ago. The car is mostly original, with 130,000 miles on it. It has a strange stumbling misfire that occurs during light acceleration throughout the RPM range. It has a small coolant leak, but it's not a problem. Could the coolant temp sensor be the problem? I get a check engine light that comes and goes randomly, and it never coincides with the misfire. Any feedback would help.

 

Not an expert but it might be your manifold gasket seeing you have the supercharger.

 

The manifold gasket was replaced along with the bearings.

 

Can you get it to misfire when power braking it under light load? If so , then either the ECM should be able to reveal which cyl(s) and/or try to short out individual plugs to pinpoint which cyl(s) are affected.