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1993 Pontiac Grand Am 2.3L SOHC 175,000 miles - Cylinders 1 and 3 not firing
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freedombet
New User
Aug 22, 2012, 5:25 PM
Post #1 of 3
(2152 views)
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1993 Pontiac Grand Am 2.3L SOHC 175,000 miles - Cylinders 1 and 3 not firing
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We have a '93 Grand Am, 2.3L SOHC, that is not passing emissions testing. We replaced the O2 sensor, per the error code on the diagnostic machine. Still had problems. We asked a neighbor who is a mechanic what the problem could be and he suggested replacing the coils, which we did. Still had the problem. We took it to the dealer who diagnosed it as bad coils/coil housing/boots. We replaced the coils again as well as the housing and boots, plus did an entire tune-up. It ran fine for about 30 minutes and then the problem came back. We took it in again to a State inspector who again diagnosed the coils. Again, we replaced the coils. Same problem. The inspector ran a full compression test and everything came back good. The motor itself is fully in spec. The inspector called his supervisor who said that maybe it was the crankcase position sensor, which we just replaced and still have the same problem. Supposedly there isn't a strong enough current being sent to the ignition coils. Does anyone know what in the world could be the problem. We have spent way too much time and money on this car only to be told the same things over and over. I'm definitely pulling my hair out and would appreciate any help I can get. Thanks!!
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Discretesignals
Ultimate Carjunky
/ Moderator
Aug 22, 2012, 5:41 PM
Post #2 of 3
(2141 views)
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Re: 1993 Pontiac Grand Am 2.3L SOHC 175,000 miles - Cylinders 1 and 3 not firing
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You sure have spent a lot. Anyone actually troubleshooting this or are they just throwing parts at it?
They need to be sure the ICM is controlling the ground side of the coils when the problem is showing. They have a special plug wire test lead set that you can use, so you can check secondary voltage with a scope. You can also check the primary voltage to be sure the ICM is toggling the coil's ground if you see your missing secondary action. It is kind of strange that your missing spark on 1 and 3 because those don't share the same coil or even the same transistor in the ICM. Since it is firing on 2 and 4 supposedly, that tells you the coils and ICM transistors are good.
If you are sure you have spark or a good secondary waveform during the skipping problem, you might want to look elsewhere like fuel injectors, which are known for shorting, and other possible PCM command input/ouput problems.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Aug 22, 2012, 6:13 PM)
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freedombet
New User
Aug 22, 2012, 8:51 PM
Post #3 of 3
(2093 views)
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Re: 1993 Pontiac Grand Am 2.3L SOHC 175,000 miles - Cylinders 1 and 3 not firing
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Thanks for your advice. Although I didn't see the dealer with their tools attached, I'm guessing they did some sort of scan. I did see the inspector with his scanner and such attached, so he's doing the best as he can figure, I hope. The inspector had us change out the coils and O2 sensor just for fun and giggles to see if it would work. It didn't. Then he hooked up something called a Vantage Pro from Snap On and showed something that looked like an EKG. Ours was really pointy looking, while supposedly it is supposed to look more like rectangles. He tested compression and the fuel injectors and all came back thumbs up. He tested the ICM and the wiring harness connecting to it and they were ok too. He was as baffled as we are. He even called in the master, master mechanic and he's the one that suggested the crankshaft position sensor. He said that these type of cars have an issue with the thrust bearings going bad and making the sensor crack. I'm far from a mechanic but I've been working on cars since I was knee high to a grasshopper and for the life of me, I can't figure out what's going on. Oh, and in addition, the temperature of the catalytic converter was off the chart. They had to literally pour water on the stick shift to cool the floor down and keep the carpet from catching fire. Ouch!
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