Help! My Grand prix has a major miss and I am at my wits end!

I have a 1994 Pontiac Grand Prix SE, 3100 v6. She developed a miss. Thinking she needed a tune up, I replaced the plugs, and the wires. No change, after
testing the ignition system, and finding nothing.. I sent her off to a mechanic. The mechanic replaced one coil pack, and said the previous was bad and the spark plugs, but the miss was still there. They did a compression check, and all seemed ok. They wanted to replace all the injectors, after $250.00 and what seemed like the throwing of parts, I took the car to a family mechanic. He's a good guy that knows his stuff, but he's stumped. I have one cylinder that the spark plug is fuel fowled. Going from the previous mechanics suggestion, we replaced the fuel injector. Nothing changed. We have good spark to all cylinders. My family mechanic thinks that maybe the cam lobe could be bad, allowing compression to check out, but not allowing fire to ignite the fuel. We are going to remove the valve cover and see how the valve movement goes, but again if that isn't the trouble, he is stumped. Does anyone have any other ideas about what could be causing the problem?
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clevere wrote:

It wasn't real common on your generation of 3.1 engine, but you might want to check for an intake manifold gasket that is leaking vacuum internally. This was much more common on the older engines that used a paper gasket. You can check this quite easily by simply removing the oil filler cap and then spraying something like brake cleen or throttle body cleaner down into the valve cover/lifter valley area. If you have some sort of vacuum leak inside there, you will notice a difference in how the engine runs. This is really just a guess.
Ian
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Sounds like that injector is being held open electrically. That's either a wire short, or a driver problem in the ECM. This can of course be ruled out, with a noid light. GW

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It seems that the small magnet on top of the cam broke or fell off. My father had a 87 Old's with a 3.8 liter V6 with that same problem. Our Grand Prix may not have one.
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