Misfiring issues with a P0300 Code

[drv2e30]

Let me tell you what I've done:

Initially I had a hesitation problem with cold starts, when the engine was hot the problem went away. So after a bit of diagnostic, I decided to replace the temp sensor, no change. So I continued to replace the fuel filter, and again no change (fuel pressure is constant at 40psi). Eventually the engine started to get worse and the check engine light came on to report a misfire on one cylinder. Which I promptly followed it up with replacing the coil packs and the wire set. After that the diagnostic code was for unknown misfire (p0300 I believe). So I then replaced the plugs incase there was a strange chance it was an issue and replaced the tps without any change. I have looked at the plugs and they are "peppered" black, which leads me to think that the timing may be off with a lean mixture. Though as far as I know the engine can't be adjusted with the coil pack system. I'm thinking about replacing the O2 sensor since it hasn't been replaced ever(at 144k+). Though I would really hate to replace it and then find out I still need to replace more parts after it.

I was also thinking about introducing sea foam into the engine via the brake power booster to see if there is a change.

Thoughts?

Sean
GAGT 3100 '97 144k+ miles

[bszopi]

40psi at the rails is low, so I'd suspect a fuel pump going bad.

[drv2e30]

Though the fuel pressure increases when I rev the engine (up to 44psi), and the chilton manual says that 41-47 is healthy. Does that sound like a failing fuel pump? I would hate to have to replace it since I have to drop the tank.

Sean

[IsaacHayes]

Well, miss fire could be ICM (ignition control modlule under the coil packs) too, but that's expensive.

[drv2e30]

Are there any sure fire methods to determine if it is that board?

[Green1995Camarov6]

some of them can be tested at Autozone, I think your injectors are dirty, there is a guy around here locally that cleans and flow tests injectors for $20 an injector. You take out the injector, he gets them to flow to factory specs...he said that clears up ALOT of misfire issues.