2006 G.P. runs rough

[ucndoit]

Hey guys, Out of no where it started running rough at first start in the morning. Took it for a short ride about 1/8 mile and it ran steadily worse engine shake and under power. After research tried to eliminate problem by cleaning MAF sensor, cleaning throttle body, and replaced MAP sensor due to it coming apart when I took it out. After each item tried to start and no engine light or DIC msg until I gave it some gas and then engine light came on and ran the same. So took it to local parts store for OBD2 scan codes were PO300 & U1000, last thing Ive done was to go back and make sure all connectors were plugged in securely. 2006 series III 3.8 V6 car ran great before this. Any help would be appreciated, thank you.

[carriedi]

P0300 is for a misfire that isn't specific enough yet. Sometime a misfire will cause a vibration in the ignition firing such that it creates echoes with the crank sensor. So then there will be some misfires that are not real misfires. When the misfire gets really bad, the specific cylinders will be recognized and the codes will reflect the cylinder. (like P0301 etc.) Hook up to a better scanner that has the misfire counter and look at the firing of all the cylinders. You will be able to see what cylinders are missing, or missing the worst, and then go to diagnosing why that/those cylinders are missing.

could be electrical, could be mechanical or could be air/fuel related. Since it shows a misfire the misfire counter will tell you it is a cylinder, a bank of cylinders, a random misfire that changes around. Most of the time it is one cylinder that is a problem. Spark, compression, fuel...

once you locate the cylinder that misses most then you can do thing to see what the cause is.

similar diagnose:
https://www.youtube.com/watch?v=I2IgGenAX0Q

you're need to hook up to a better scanner and check all the modules. See if a module is not communicating all the correct parameters to the other modules. (U1000)

[Guest]

Here is an update, I put it in the shop and they stated the IMC had shorted out damaging the coils and they pulled a couple plugs which looked bad and also wires looked to be original. They recommended replacing IMC, Coils, plugs & wires with AC Delco parts. So that's the plan at this point.

[carriedi]

let me know how it turns out

what's the IMC? ICM - ignition control module?

did they switch your parts around to see if the misfires follow any particular piece? Switch coil to another coil, to see if the miss follows the coil or stays in the same place on the misfire counter? If it stays in the same place switch the wires to known good cylinders? If it is still the same cylinders then switch the plugs to known good cylinders? If it's still in the same cylinders check the fuel injectors...

If it follows any of the parts you moved then the part you moved is probably bad. Replace the part and see if the miss is gone.

If the ICM killed a coil, switching coils did the miss follow the bad coil? Did the ICM kill the good coil that was working before? Or is the ICM not firing the coil that is misfiring? Anyways, let me know how it works out.