Engine Performance problem
2003 GMC Yukon V8 Four Wheel Drive Automatic 115000 miles
I first had trouble with a lack of power and than a the engine light came on and I got codes P0300 and P0430 and after looking in your archives here I found information about an ECM ground on the engine block so I cleaned those up and put some electrical grease on them and it got rid of some noise on the radio that had started about two months ago and when I pulled the truck out of the shop it seemed to have a lot more power than it has had for a while however when I got it up to speed on the highway the engine light came on again and it lost so much power it could barely maintain highway speed. When I pulled the codes again I got P0101 and P0300. I cleared the codes and and as soon as I gained any speed the codes came back sometimes exchanging the P0300 code for P0306. I checked the grounds again to make sure I didn't miss putting a wire back on and I didn't find anything wrong and I checked the wires on the mass air flow sensor for damage and they looked to be ok. I am not running and have never used an oiled air filter and the sensor looked very clean. The truck is now running so rough it is not drivable and I don't know where to look next.
P0101 is for MAF sensor performance try cleaning with MAF cleaner. The 300, 306 are engine misses the 430 is TWC cat due to miss. Faulty MAF is most likely the problem but would need diagnostic scan tool to verfy.
Hope this helps
Thanks for donate
March, 26, 2010 AT 1:23 PM
MAF sensor checked out ok, was cleaned and then changed with no improvment. I took it in to a shop and they finally figured on a plugged converter so they changed out the cats and it straightend out for the most part, it runs smooth and has decent power again but now it has a tap in the right side just like a lifter so they pulled off the head and changed all the lifters on that side and it improved somewhat but definately did not go away. Also the oil pressure is noticeably lower once it warms up. When the tech changed the oil after changing the cats he said it was very thick and almost tarlike. I had just changed it and it had less than 600 miles on the oil change. I'm thinking maybe this motor needs to be flushed out as it may be partialy plugged or would you suspect the oil pump. When the head was off the tech said everything looked like brand new inside. I was thinking that the plugged converter must have caused the oil contamination but I've been told that a converter rare'ly plugs unless unless there is something causing it. I don't want to spend too much more time on it as I can get a used engine for about $1000 and change it myself. I was just wondering if you have any other ideas?