I have a 93 GMC 1ton truck that had california emissions and a throttle govenor on it (Rochester TBI) The govenor malfuntioned on it and it was annoying so I replaced it with a federal emission TBI from the parts shed (no idea what year{I do know that it is an OEM Holly TBI}).

The difference in power is amazing! but with the new TBI it won't idle for more that 120 seconds. At exactly 120 seconds the RPM's start to drop and then bounce back and the engine boggs down and dies. I replaced the MAP sensor, TPS, Idle air speed motor, the entire fuel system from the fuel tank forward and the coil, cap and rotor, plugs and wires with no change in symptoms .

Then in desperation I went to the junk yard and got 2 "blue keys" for the PCM. My idle problem was instantly gone when I plug in either of them! Bad news is that it runs rough with no power and won't shift. Both keys came from trucks with the 4L60E trans, mine is 4L80E. So now I'm diving into learning about reprogramming!

I'm really excited to be learning how to tune, I'd really appreciate help getting this sorted out. After I figure out how to get my truck to idle, I want to reduce the fuel pump cut off speed on my wife's 97 3/4 ton chevy from 99mph down to 78mph to minimize tickets

I have a few questions:

* I have the blue Key, why is everyone switching to earlier or later systems?

* do I need to erase the program that are on the new chips currently or will they be overwritten by the ALDUI box when I plug in Tuner Pro?

* If I do need to erase the blue keys, is this done with UV light like some other chips?

* If it is erased by UV, can I just leave it in the sun for a day ;Sunlight has MASSIVE UV!

*Is there anything I'm missing or should know about before getting started?


This is what I have discovered so far on this AWESOME FORUM!

$31 is for the 4L80E trans

This is where you find your program files:

http://www.gearhead-efi.com/Fuel-Inj...our-files-here

You need to down load Tuner pro: http://www.tunerpro.net

You need to buy this cable AND this ALDUI box to talk to your PCM: http://www.moates.net/aldu1-and-cabl1-p-127.html

Here is a tutorial to get started http://www.gearhead-efi.com/Fuel-Inj...a-must-read!-)