Some more ignition help

[pickens]

Okay, here's the deal. I have basically changed everything important in my ignition system. I've changed my power transistor, coils, wires, and plugs. I was chasing a random misfire at around 2-3k rpm. I finally narrowed it down to the coil (process of elimination). After changing everything else, I started to get a weak spark, so weak that I had to gap the plugs down to .020 so it would fire at 15psi. So I changed the coil and wallah.....the ignition system worked like brand new. It's been a couple of months now, and I'm starting to get a weaker spark again. So, I'm thinking my coil is going bad again. But there has to be something wrong somewhere else to kill another coil. Thats where I'm stuck. Maybe its a short or something. Any ideas would be helpful. It could also be that I just got a bad coil from when I bought too. If it matter I'm running the ngk 7es plugs gapped at .028 and the motor is starting to mis under boost. I hope all this makes sense.

 

[GTM]

Originally posted by pickens

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After changing everything else, I started to get a weak spark, so weak that I had to gap the plugs down to .020 so it would fire at 15psi.
...
and I'm starting to get a weaker spark again. So, I'm thinking my coil is going bad again.
...

I'll toss out if that is 15psi _boost_ and not compression pressures and you are seeing that as a real number a lot of the time then the plugs may be breaking down. Certainly a wider gap will cause coils to overheat so running at .020 would keep them cooler. However, if the plugs are breaking down and it's taking more power to bridge the gap because it's arcing way up inside the plug first you could be toasting the coils. You could try another step colder plug with the proper gap. Many years ago I got stuck on the road with a single cylinder motorcycle with some unknown plug. Found a parts store, made a guess at plug and cranked it over. Before I ever got it in gear the plug had fried so had to go 2 steps colder and that didn't last but a month. Point being compression pressures and heat ranges play a big part in how the engine is going to perform. The problem of sorts is you will have gotten use to the acceleration with the .020 gap but suffering gas milage. Opening them up for a long road trip will improve milage but acceleration will suffer including pinging.

I don't know if your car has dropping resistors on the coils for normal running which get bypassed during cranking conditions to get 12v+ to the coils when they would normally be running at 9v. Should it get stuck in the bypass and running always at 12v would most assuredly speed up their demise. So plugs may be in order and determining if you have dropping resistors and are they working properly.

A malfunctioning EGR can also contribute to wasted plugs but this is usually found on the cylinders closest to the EGR dump. Too lean a fuel mix, fuel pressure too low, vacuum leak, can also take out plugs. Hope something in there solves the problem besides not running that much boost.

Cheers,
GTM