94 GP 3.1 shakes BAD and will not pull itself

I just bought this car and don't even have it home yet. The guy said a mechanic told him it was a coil pak. I hope that's all it is. Is there an easy way to check this? I'm figuring the first thing I will do is find my spark tester and try to figure out which ones are getting fire. He said he put new wires on it. If I remember correctly I could move the coil pak to a different position to see if the spark follows or not correct? Sorry, I know I'm getting the cart before the horse but just thinking about my plan of attack when I get it home...LOL
Oh yeah it has 127k on it and it is in pretty good shape other than this problem. $600 so I sure hope the engine isn't toast or something.
Rob

Hi Rob,

A quick and simple test to check coil packs is to remove all the plug wires at the coils, then have an assistant crank the motor for a few seconds. As the motor cranks, you should observe sparks jumping between the two consecutive coil towers on all 3 coil packs.

If you do not have spark on a coil pack, then you can swap them around to see if the no spark condition follows the coil pack or if its a zorched ignition module.

Thanks Tblake...I just got it home and got a run at the garage and actually got it in there. It is pretty sick running. Ok did you test and all coil paks have spark. I also tested them one wire at a time at the coils and they all fire with a spark tester. It looks like the guy that had it already replaced the coil pak and module under it with a used one. It has white paint on it (like from a salvage yard) so he lied about it needing a coil pak. (big suprise)
Anyway, it also looks like he has been messing with the ECU...it is loose in there but does not look new, nor has white paint on it. Is there a (usually happens) thing on this year where I should start looking? It backfires (pops) through the intake a lot and seems to hump up when you turn it over. Then suddenly it wills start and run although missing bad and will actually move...but like 30-40 seconds later it will pop loud and suddenly quit. Just like you turned it off. Then it might crank for a long time before it will suddenly start up again and run missing again for a very short time. What do I check next? I will get the code reader from dad tomorrow but I doubt it will tell me much.
Rob

It almost sounds like the ignition wires have been mixed up. I would check the firing order and make sure the wires are going to the proper plugs. Good Luck!

I checked the wires first thing because that is exactly what it runs/acts like. Seems like it is firing all out of order.
Any other ideas? I don't know what to check next.
Rob

I better get you an ignition wire routing diagram. I think a wire (or wires) are plugged in the wrong spot.

Maybe someone swapped coils around and didnt put the wires in the right spot in relataion to the ignition module. (seen it happen). The stock coils have numbers on them of what cylinders they should go to, but the coils could easily be switched around and the next person who works on it will have no idea.

Messing with the ECU scares me. If he replaced it, I hope he kept the PROM chip out of the old one and installed it into the new ECM. Tracking down a prom chip for a specific car from what I hear can be quite difficult.

Stupid question probably, but is the SES light on?

Pay no attention to the numbers on the coil towers, unplug all the wires at the coils and try this out.

http://img188.imageshack.us/img188/8991/3100timing.jpg

Tblake, thanks much for the diags. I found a haynes manual that I had for a Grand Am with a 3.1 and had already checked the wires. I'm pretty sure it is the same exact engine and diag you just sent. I'll double check but it looks the same. I traced all of them and made sure they were on correctly. Someone has replaced the coil pak and module under it with one from a junk yard. I was sure hoping it was a crossed up wire. DANG!
Rob

Any other ideas? I guess the ECU could be causing this problem?
OH Yeah...it does have the SES light on and I got the code reader from my dad but it only fits the newer OBD I. I was thinking you could jump the a b pin and get the code but this car don't have a "b" pin in the hole?? How weird is that...

Rob

...OH Yeah...it does have the SES light on and I got the code reader from my dad but it only fits the newer OBD I. I was thinking you could jump the a b pin and get the code but this car don't have a "b" pin in the hole?? How weird is that...

HAHA No, your code reader probably fits older OBD1 vehicles. 94 was the beginning of the crossover year where OBD2 was being intergrated. I have not yet been able to scan a 94 GM vehicle with the paperclip trick.

About the only way you are going to be able to pull a code is to bring it to the dealer or buy a scanner that is capable.

Have you checked fuel pressure? Pull the spark plugs out and see what they look like. While you have them out it might be a good time to check compression.

You could also do a cylinder drop test to see if you can pinpoint exactly what cylinder(s) are missfiring. It requires the car to be running though.

I wonder if unplugging the MAF could help? Might be worth a shot.

Well it was not the MAF sensor and all of the wires on there corectly. All of the coil paks are firing. I'm stumped. I took it to a little shop up the street. He is messing with it. Said they took the valve covers off to make sure non of the studs came out on the rocker arms but said it was fine. Did a compression check and that was also good. He is going to look at the injector wiring and injectors today. He sounds stumped too.
Rob

Crazy, I'm afraid he replaced the ECU due to failure and didnt swap the prom chip over and possibly just threw one in there he found. Thus causing drivability problems.