Pontiac Repair: 1992 pontiac grand prix, pontiac grand prix, vacuum leak

Question
my 1992 Pontiac Grand Prix is running very rough & has multiple problems. First the air conditioning vent will no longer switch from top & bottom vents to the front vents, Then yesterday the engine started idling rough , especially when you stop. Also the transmission started shifting hard at times. A mechanic told me that it might be the ignition module. how do you remove & replace it?

Answer
Hi Don:

First off I just got this question it was stuck in the deep end of the "question pool".. There could be a couple of issues here. I wouldn't lean towards an ignition module unless the engine has a couple of dead cylinders. You can check for spark with a spark checker you get at the auto parts store. This could have something as simple as a vacuum leak into the car I can't remember for sure but that can has a vacuum solenoid assembly that runs all of the HVAC mode does if that's the case that would be why that stopped working. If it had a bad enough vacuum leak it woul make the engine idle high and very erratic.If this car has a 4 speed transmission then that vacuum leak could also affect the up and down shifts the 4 speed transmission has a vacuum modulator to control how hard it shifts. This could all be out the window if the engine is just plain running poorly and has weak manifold vacuum due to the way it's running not from a leak.. just a few ideas, without seeing it it's hard to tell you eaxactly where to go with it but my guess is that they are all related somehow. Oh one last thing if you know wher the engine control module is on this car you may want to just gently tap on it with the plastic end of a screwdriver and see in the engine want to stall or acts up at all. Those control modules were known for cauing all kinds of idle/stalling concers. Good Luck :)