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Last weekend while driving my '93 SSEi it began shifting a bit oddly and then had very little power when accelerating, especially when boost was above 0 PSI.
I suspected a bad coil pack because similar symptoms on this car occurred about 7,000 miles ago and were caused by the coil pack for cylinders 1 and 4. I suspected that one of the other coil packs had failed this time (because I have never replaced the other 2) but to my surprise it was the coil pack for cylinders 1 and 4 again. I replaced it and the car runs fine again.

What are the chances that the cylinder 1/4 coil pack has failed twice in the last 7,000 miles? I've never had to replace the other 2 coil packs, and none of the coil packs on my '92 supercharged have been replaced. Is it possible that something's causing only the cylinder 1/4 coil pack to fail?

Also, I have a question for the gearheads: I assume that when a coil pack fails, the injectors for the affected cylinders still deliver fuel, so unburned fuel is passed through the exhaust valves and to the catalytic converter, right? Or is the ECM smart enough to cutoff fuel to the affected injectors when it detects no spark for those cylinders?

Thanks.

Might even want to try a different ignition module. How did the terminals look that plug into the bottom of the coil? It might not be a bad coil, but a bad connection. Did you do the coil test in tech info?

Sorry, I should have noted that it wasn't simply a bad connection, and the terminals looked good and weren't loose or corroded.
My digital multimeter showed open circuit between the two spark plug terminals on the failed coil pack, and this is what happened to both of them before I replaced them.

Billha wrote:Also, I have a question for the gearheads: I assume that when a coil pack fails, the injectors for the affected cylinders still deliver fuel, so unburned fuel is passed through the exhaust valves and to the catalytic converter, right? Or is the ECM smart enough to cutoff fuel to the affected injectors when it detects no spark for those cylinders?

Thanks.

That is a correct assumption. The PCM isn't smart enough to cut fuel on a specific cylinder or pair. It keeps putting fuel down into a dead cylinder and assumes it's going to light eventually.

I would also check the ignition module under the coil packs. Have you checked the windings on the "bad" pack for resistance yet? Simple test would be to swap a working coil into the 1/4 position and see if the problem follows the coil pack. If the problem dissapears during this test, then clean the heck outta the contacts on the primary side of the coil.

Never mind: typing at the same time. Check you plug wires over, look for anything arcing to the block and burning up the secondary winding on the coil. Something smoked the coil, and it's probably still happening.

The 1&4 coil failed on my 93 SSE (150K mi) while I was on a road trip. Car started shaking very badly. I thought it was loose front wheel bearings--it was shaking that bad--since I had just replaced them. Had to go to a Pontiac dealer to find out what was wrong, and $159 later they told me it was the 1&4 coil pack. I stopped by O'Reillys and got two more, then replaced the other two myself. For a lot less than $159. But I dont have 7000 miles on the new packs yet so don't know if that is a magic number or not. Sounds to me like you got a bad "new" coil.