Anyone using a Hypertech Power Programmer III (HPPIII) for the LT1, that was bought when they were first introduced (maybe 3 years ago), should suspect a possible fault within either the program or the electronics. However, only if the engine has some unexplained glitches in drivability. The symptoms are poor high rpm peformance (above 6,000 rpm)--typically a misfire, poor performance at low rpm when in a top gear (around 1300-1400 rpm or lower)--the engine just makes noises like it is wheezing and will not accelerate, sometimes it will come close to or actually "cough" thru the intake manifold. One final symptom is that the engine will run pretty well for about 20 miles after any change is made to any engine managment or smog control item, then when the 20 miles is up, it'll run like crapola again.

The way to find out that it is the Power Programmer and not the engine or PCM is to backload the power program into it's module, thus returning the tuning to stock. Give the PCM about 20 miles to relearn the "Integrator" or short time tuning, then about 200 miles to recurve the "Block Learn" or long term tuning. If there is no change, then the Power Program is ok. The problem is that the base, or stock program is overlaid with a defective program by the HPPIII--this is the stock Block Learn parameters. If the HPPIII modified program is defective within the PCM, then the PCM will continue to compare the Integrator with the Block Learn and continually try to modify the base program or Block Learn. In short, the PCM then has a faulty program and the car runs like crapola.

Passing on info received from one of our club members......and thought it would be good info for those out there experiencing problems with (HPPIII) on their LT1...... :seeya