I have a 2002 GMC Savanna van with the commercial 6.5 in it. They kept the 6.5 in the commercial vehicles for several more years. Its a redesigned engine and quite often very different than the pre 2000 6.5's.



Problem is that the turbo is erratic, works fine until engine it up to temperature. When the engine is warm the turbo surges for lack of a better word. It boosts for @ 5 seconds then it stops for @ 5 seconds and keeps cycling like this. Sometimes it won't even do that, under high throttle it comes on but them over compensates and the pressure go up to 18psi. As I said it works as it should until the engine is warm.



We use the van for towing so its a pain in the a@#. I have been trying to figure it out for almost a year now. The things I have done:



New waste gate valve

New waste gate solenoid

New map/boost sensor on manifold

Vacuum pump was new 3 years ago and has 24psi in the lines steady pressure

New injection pump a year ago (irrelevant)