I have some questions before jumping in

**samdaven** · 07-23-2019

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 99 mph down to 74 mph

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?

**1project2many** · 07-24-2019

Throttle body with injectors may not deliver same fuel per pulse as the throttle body that was removed. Need to determine if injectors are different.

4L60E and 4L80E programming are different. You need a 4L80E program.

"Blue keys" are called memcals. The "blue key" part is used in millions of computers. The chip inside is programmed for specific components. Mix and match yields random results. Find four letter code on memcal or on chip inside memcal. Find service number from pcm. Find throttle body number from replacement TB. List engine size, final gear ratio. Maybe we can get you straightened out.