Expert: Harry Jacobson, P.E. - 1/22/2005

Question
hello I have a 93 6.5 turbo diesel when i am driving and stop at a light and when i slowly touch the gas it speeds up and surges thanks for any information

Answer
1993 was the last year of non-computer-controlled GM diesels.  Your engine should have a mechanical linkage between the accelerator and the injection pump.  Later models use a "drive-by-wire" accelerator and there is no direct mechanical link from the accelerator to the injection pump.  I point this out because you need to make sure that your engine has the mechanical linkage and that the linkage is free from binding.

Another reason could be a defective cold start circuit that is causing the fast idle soelnoid and housing pressure cold advance (HPCA) to stay engaged after the engine has warmed up.  At the injection pump, there should be a big pink wire and two small green wires (one of which may be connected to a second spade connector on the injection pump.  Disconnect the gree wires and try driving your truck.  If the problem goes away, you either have a short in the wiring or a defective sensor.

The transmission on your vehicle is electronically controlled.  There may be issues with sensors or the controller.

Many auto parts stores will read diagnostic codes for free.  You may wish to have your vehicle checked for any codes.