2003 surging under part throttle load

[mrhockey]

I did a search back to 2005 here on the board but most surging issues were related to idle problems. My Duramax has about 75000 miles on it. I use it mainly to tow my car and trailer. I have a TST programmer on it that is only slightly tuned up. The truck runs fine most of the time but every so often the truck surges under part throttle load. I am cruising along at about 2500 rpms with very minimal boost and EGT readings around 900-1000 and suddenly the surges begin. I can't tell if it is the trans slipping or other issues. The trans was flushed about 5000 miles ago. Any ideas?

[DmaxMaverick]

Welcome aboard!

There are a few things that can cause this. Filters, air and fuel. Either of them can cause problems when they need service.

Your programmer. Try repeating the condition with it removed. "Fishbite" has been reported for all the programmers, from time to time.

FPR. The Fuel Pressure Regulator could be getting tired or fouled. No way to test it w/o a scanner or Tech II. The desired/actual fuel pressures need to be observed under various conditions. A plugged fuel filter will also effect the fuel pressure.

Injectors. Unless they are way out of spec, or you're making oil, it's unlikely, but possible. High return rates can also effect fuel rail pressure (FPR).

I suggest change a filter change, remove the programmer, and try to duplicate the problem. Other than that, you need to get a scanner hooked up to see what the computer is seeing.

[mrhockey]

Thanks. The only thing I saw that even resembled my issues on another board were attributed to the guys fuel rail sensor. I would be lucky to duplicate the issues unless I left the truck and probably the trailer with a shop and left them drive it for a while.