Chrysler T&C 3.8 2003,Rough idle, bad PCM, Misfire #3 & 6 cyl, diagnose/test
 

I have a 2003 Chrysler TC 3.8 that idles rough and has an inconsistent miss at all rpm. It started at 92,000mi and for about 4 years this problem was only a slight miss and no codes registered. Now at 185,000mi the problem and gotten a lot worse (or maybe a new unrelated problem) with the misfire codes P0303 and P0306 (misfire #3 and #6 cylinders). I have done the following diagnosis/test and codes keep resetting:
• I have done compression check and all cylinders pretty even 145 psi and above
• Pressured each cylinder up 120 psi and checked for bubbles in radiator – no bubbles.
• I have installed plugs, coil pack, and plug wires (Mopar)
• I have checked for chafed wires by the firewall and all are good
• I have cleaned & bench tested each injector – all are good (replaced all bottom O-rings)
• Checked for voltage to injectors (used a bulb and saw the pulses)
• Smoke tested for vacuum leaks – no leaks (replace cracked hose on canister under driver’s seat)
• Cleaned carbon from the throttle body and new plenum gaskets
• Checked signal voltage on Throttle body sensor - .7V closed and 3.8V WOT
• Checked IAC motor – hooked 12V which made pintle move out
• Checked for broken valve spring on cylinders #2, 4, 6. No broken valve springs
• Used MAP cleaner on the MAP sensor
• Checked PVC valve – good rattle.

My next step will be a leakdown test on all cylinders, then possibly take it to the dealer for PCM etc. test. If anyone has some technical advice or concrete test to try, I would appreciate your feedback. I will be working a lot this week and may not be able to respond, but really appreciate your help.

If I have a bad PCM, does anyone know what has to be done to install a used PCM (flash, reprogram etc.)? Thanks.

You might have more of a response if you post your question in the T&C forum further down the front page of the site. That's a very active forum with many T&C owners chiming in regularly. You have posted in the "Forum Issues" section which is for people having issues with the forum. For issues with your car, post in the car forums.

Beyond that, there are services on the web which will sell you a replacement PCM on an exchange basis. I found one on eBay and replaced my Sebring's computer for about $200. It was a snap and more than a thousand dollars cheaper than the dealership.

OK, thanks.