Questions and Answers

Pontiac Grand Prix No Spark Q. I have a 1991 Pontiac Grand Prix with a 3.1 liter engine and it will start and run for about five minutes and then stall. It then has no spark. The next day it will do the same thing again? The next day (before even starting it) I tore the ignition module and coil packs off and brought them in to the auto store and they tested the module and all three coil packs (primary and secondary), they all tested out good.

So I then decided it must be the computer so I installed a new computer but it continued to do the same thing. What I was wondering is, could the module test good when it is cold and bad when it starts to get warm? It doesn't seem very likely that all three coil packs would be bad after they start to heat up in which case it would still have some spark in two out of three coil packs.

I also heard that if a coil pack goes bad this could damage the module, so would everything have to be replaced if this was the problem? Or do you have any other ideas on what else could be wrong or tested?

Thanks,
Mike

A. You are overlooking the Crank Angle Sensor (CAS). This is in the block on rear. Sort of hard to get to on your back. It could be causing this. Yes, a module can test good and turn bad when hot. If you have a bad spark plug wire that allows spark to jump at the coil this could spike the module and in time will give you a dead coil. (Coil will be good but module will not fire it). My guess is the module or the CAS.