Hello gents, I usually hang about in the diesel section of the forums and everyone in FTE has been great to me. So figured I'd get your advice.

Truck had the p0301, p0171, and p0174. I used a scanner and figured out lean on bank 1 and bank 2 with number one cylinder misfire. It started to run a tad rough but not too bad until your put it under a load. Then it sounds like I hear detonation and will not get RPM's over 3k no matter how hard you accelerate. It falls on its face. I replaced the COP and cleaned the MAF sensor with MAF cleaner made by CAC and replaced the fuel filter. The IAC valve was replaced about 2 months ago.

Now after I replaced the COP and cleaned the MAF it seems to idle ok but still gets the detonation aka spark knock with no power under acceleration. But no codes now.

So I have been searching around and it seems like either a vacuum leak or catalytic converter is plugged. Ive sprayed carb cleaner everywhere and nothing seems to change the idle that would indicate a leak found (to me anyway). I have hooked up a vacuum gauge to the brake booster line and ran the motor. Im getting 22Hg at idle and it maintains as i rev the motor more. If I punch the throttle fast it will drop to about 5Hg for a split second but recover. Im not hearing backpressure or getting the smell that would indicate a plugged cat, but who knows.

Please help a brother out....I travel for work during the week and I cant let mommy keep driving my truck. She rides too many curbs!!!

 

Sounds like you could be having an issue with the digital transmission range sensor (DTRS) down on the transmission. When in neutral or park the ECM kicks in a rev limiter around 3K to prevent damage to the engine since it has no load on it. Even though you are in drive and moving, if one of the contacts within the DTRS is reporting to the ECM that the tranny is not in drive, then both the rev limiter is kicking in and the spark advance is not being properly controlled.