96 Grand am GT running problem, 2.4 stick

[crabgt]

The car was acting like it was running on 2 cylinders, so I scanned it with a hand held and got no codes. Pulled the spark plug cover to find 2 were black on the left, and the right 2 plugs looked ok. Replaced the left coil and all 4 plugs thinking the coil might be dead, same result with no change. I do smell fuel out the exhaust and wonder if I was premature on thinking it was an electrical issue, but now wonder if it could be hung injectors. There had been some misfire issues for about a month under load, which lead me to think electrical, the car has about 135k. Hate to start replacing a $185 dollar module or computer without some idea thats where I should be looking.

[crabgt]

bump

[Headnsouth]

What kind of plugs are you running?

[crabgt]

Originally Posted by Headnsouth

What kind of plugs are you running?

They were AC, I put in some Autolite double platinum since the choices were limited last night but no change. This is a major misfire issue, won't hardly run.

[Headnsouth]

Wires are good?

[crabgt]

Originally Posted by Headnsouth

Wires are good?

No wires, direct fire.

[Headnsouth]

Have you done a compression test?

[crabgt]

Originally Posted by Headnsouth

Have you done a compression test?

no

[Headnsouth]

Testers are cheap just get one that screws into the head and start there.

Engine Compression Test
Perform the following steps in order to conduct a compression test for VIN 4:

Conduct the following steps in order to check cylinder compression:
1.1. Engine should be at room temperature.

1.2. Disconnect wiring from the ignition module

1.3. Remove the spark plugs.

1.4. Throttle body valve should be wide open.

1.5. Battery should be at or near full charge.

For each cylinder, crank engine through four compression strokes.
The lowest reading cylinder should not be less than 70% of the highest.
No cylinder reading should be less that 689 kPa (100 psi).
Important: The results of a compression test will fall into the following categories:

Normal -- Compression builds up quickly and evenly to specified compression on each cylinder.
Piston Rings -- Compression low on first stroke. Tends to build up on following strokes but does not reach normal. Improves considerably with addition of oil.
Valves -- Compression low on first stroke. Does not tend to build up on the following strokes. Does not improve much with addition of oil. Use approximately three squirts from a plunger-type oiler.

[crabgt]

Originally Posted by Headnsouth

Testers are cheap just get one that screws into the head and start there.

Engine Compression Test
Perform the following steps in order to conduct a compression test for VIN 4:

Conduct the following steps in order to check cylinder compression:
1.1. Engine should be at room temperature.

1.2. Disconnect wiring from the ignition module

1.3. Remove the spark plugs.

1.4. Throttle body valve should be wide open.

1.5. Battery should be at or near full charge.

For each cylinder, crank engine through four compression strokes.
The lowest reading cylinder should not be less than 70% of the highest.
No cylinder reading should be less that 689 kPa (100 psi).
Important: The results of a compression test will fall into the following categories:

Normal -- Compression builds up quickly and evenly to specified compression on each cylinder.
Piston Rings -- Compression low on first stroke. Tends to build up on following strokes but does not reach normal. Improves considerably with addition of oil.
Valves -- Compression low on first stroke. Does not tend to build up on the following strokes. Does not improve much with addition of oil. Use approximately three squirts from a plunger-type oiler.

I can test that, but fairly certain that its not the issue here.

[J-Ri]

1 and 2 are not companion cylinders, so the coils/ign module is not the problem. I would disconnect the injectors for cylinders 1 and 2 and check them for resistance. I can't give you a number, but all injectors should be within an ohm or two. If they're all equal, check to be sure they are firing (or being commanded to) with a noid light. It's basically just a small test light that connects in place of the injector, but don't use a test light because they can draw too many amps and take out the computer.

Are the plugs fuel-fouled?

[xeroinfinity]

If you only replaced one coil you might as well replace the other one. Along with the boot connectors, everything under the top cover.

Its probly your ICM (Ignition control module), some part stores can test it for free before you buy a new one.

Misfires can be both Ignition related and injector related.

[crabgt]

Originally Posted by J-Ri

1 and 2 are not companion cylinders, so the coils/ign module is not the problem. I would disconnect the injectors for cylinders 1 and 2 and check them for resistance. I can't give you a number, but all injectors should be within an ohm or two. If they're all equal, check to be sure they are firing (or being commanded to) with a noid light. It's basically just a small test light that connects in place of the injector, but don't use a test light because they can draw too many amps and take out the computer.

Are the plugs fuel-fouled?

Yes, fuel fouled black, no fire.

[crabgt]

Originally Posted by xeroinfinity

If you only replaced one coil you might as well replace the other one. Along with the boot connectors, everything under the top cover.

Its probly your ICM (Ignition control module), some part stores can test it for free before you buy a new one.

Misfires can be both Ignition related and injector related.

Will do on the way home.

[crabgt]

Module tested good, but talking to a guy behind me that had the same issue with the same year car said his did also and when replaced fixed the problem. Going to visually check for plug fire on all 4 and make sure the tower is good, coils test fine.