Originally posted by DennyW
Absolutely, check codes first thing. If you have already changed the 02 sensor, and checked the egr, and it's a vortec motor, and cleared the codes, but they return after a short run, most likely the injectors are bad, leaking. Especially if you get an 02 sensor right or left bank code, or egr code. Because it causes the system to run rich, and gives you a false code for them being bad. The computer is trying to correct the rich mixture, and goes out of limits.
I agree if its a vortec its leaking down, when did they come out with the vortec.? I fixed a 3.8 the other day on here with a temp. sensor code. no comment on my drawing?