I am new to the forums but it looks like a busy place so I thought I would spill my problems and give it a try. My 96 5.7 is in a 2500 truck with about 150 000 miles and is missing and getting very poor milage. I have had it at 4 different shops(2 Gm dealership and 2 private) and no one seems to be able to help.
Shop 1 (private shop) I took it there cause my check engine light was on and had no power. Missing down low and surging at higher rpm. code showed up as O2 sencor so he replaced, ran o.k. for 2 miles, light back on. turned around scanned it said bad MAF, TP, and two more O2 sencors. I had a hard time believing so cleared codes and left. Ran o.k. for a few 100 miles
Shop 2 (gm dealer) told me that the timing chain had skipped for sure and that there was no use doing anything else till that was fixed. I left there knowing that there is no way on this earth that the chain had jumped cause these motors have a plastic cover that would chatter if that where to occur.
Shop 3 (private shop) Installed his scanner, which shows no codes or any miss fires of any sort, yet the truck dash is shaking so hard at idle I cant even play a cd. He said he seen it lots and laughed at the gm dealer for not figuring it out, it was the distributer for sure with out a doubt. Installed new distributer, not one little bit different. Wont return my phone calls (suprise)
Shop 4 (Gm dealer) Scanned it, nothing electrical showed up, told me low vacuum at intake, cam lobes gone for sure. I take it home pull the motor, looks like brand new inside. Call them back, wont talk unless i bring the truck back. 107.00 an hour they charge. I guess they will talk for that much. Cost me 347.00 just to put it on their scanner.
Here I sit now. I have about 3400.00 into the truck now, and it still runs really poorly. It starts good, misses slightly at idle on passenger side, no power, getting about 6 mpg, mid range it bucks around, surges at higher rpm. At 60 mph in OD it will not gain any speed until you push it far enough to make it shift down. If you dont push it far enough the dash and everything shutters real hard, been running it without a hood and I can see the engine flipping back and forth if you put a load to it and dont let it rev.
A friend of mine let me borrow his truck for the weekend, so I went to work. I swapped everything from his to mine and mine to his. Injectors, MAF, EGR, Top part of intake and all sencors on it including throttle body assy. Cam sencor, basicly every thing that I could without pulling motors. His keeps running good, mine, well...
here is a list of what has been done or tested
compr 150. psi all dead even, cyl leak down 8 to 10%. the following are new parts--- plugs cap rotor distributor timing chain new intake gks plug wires fuel filter cat convertors, 02 sencor, ign coil. I tested fuel press
I do believe that it is more then just one cyl missing it has to be something else that i am missing. I took the good running truck and pulled one wire to simulate one cyl missing, still had way more power and ran smoother than mine. I think I would have to pull 3 or 4 wires. It also isnt a miss that you would get off one cyl, as it has no rythem to it, the miss is all over the place. One more thing, my charging light comes on at high rpm, 4000 and above, cant really explain that but might be related?
If any one has any ideas, let me know. Any help would be great, other then that, if any one wants to buy a good truck, I might have just the deal for you.
Thanks