I have a truck I bought for towing equipment and have a problem that the dealer and several independant shops can't figure out.
When purchased, it ran a bit rough so I did a tune up, plugs, cap, rotor, wires etc. That smoothed it out a bit, but it still acted like it was running lean. It would ping under a load and just generally seemed to be straining. It would also lurch when in 1st gear and idling. I checked the timing (it was right on) and even tried retarding it to see if that made any difference. No luck. Used Premium fuel and Octane Booster. Same result. Checked for vacume leaks, could not find any but went ahead and changed all of the vacume lines. Still the same results.
The following is a list of parts replaced by myself, the dealer and independant shops. Air pump. Oxygen sensor, Map/ Barametric sensor, IAC valve, EGR valve, fuel pressure regulator and PCV valve.
I have tested the fuel pressure, fuel volume, Air charge sensor and Coolant temperature sensor. All have tested at correct factory specs.
The only positive results I had was when a local tune up shop cleaned the fuel system with the truck running. The truck ran great, but only for a day. Then back to the "same ol same ol".
I have checked the on board diagnostics and get a fault #41 with "key on engine running". My Chilton's manual references this to "Oxygen sensor circuit indicates lean", or "No oxygen sensor switching detected".
With the key on and engine off I get fault #22, "BP sensor or MAP out of range" and fault #32, "EVP voltage below closed limits".
I don't know what these are telling me. Anybody have any ideas?
Any help is appreciated!

 

Have you done a KOEO (key off engine off) test?

 

Yes, I have done a KOEO test. That is where I got the #22 and #32 faults.

Any ideas?