I have an '86 Iroc clone that according to the vin code use to be a six popper Sport Coupe. The 5.0 that was in it ran great but a little rich. The 5.0 is tpi and looks like an '86 engine (see pic). The swap looks complete and professional as though dealer installed. So I rebuilt a L98 5.7 from an '88 GTA and dropped it in. Street strip cam, mild head & intake port & polish, roller rockers, gear drive, headers and Accel ignition. Now the 5.7 computer won't start the car but the old 5.0 one will. I kept the same harness because the Painless Wiring harness was the same part # for '86 & '88. The '88 computer clips right in. There is also a Bosch unit attatched to the computer w/ it's own harness, what is it? Can the 5.0 unit be programed to run my 5.7 right? The car runs great with the 5.0 computer but I can't help think I'm missing out on some power. Thanks for reading, any help?

 

I thought the only difference between the two, that mattered anyway, was the PROM? If you have 350 sized injectors, 350 knock sensor, and a 350 prom, it should work. At least thats what all the FI swap guys always say.

 

It won't even start. what the hell is the bosch box attatched to the computer? Is it engine specific? What is the correct way to install a different computer? Am I loosing power with the 5.0 box?

 

Did you install the 350 PROM in the computer? If you did this, and have the 350 knock sensor and 350 injectors, it shouldnt be a problem.

 

Can't be less power than the engine not running.

Put the 305 stuff back in. MAF is not nearly as sensitive to changes as SD is.

 

what do you mean put the prom in the computer?
I just installed the box that said ecm?
Maybe I just don't know what I'm doing.
I would like to, if possible install, a adj fuel press reg to make up for the higher fuel demand of my 350.

 

Could it be the VATS on the 88 prom

 

well I think your problem lies with the difference in the ears, the 86 ECM may not have VATS in it but the 88 one will. Vats is what keeps the car from starting without the proper key in the iginition. I think your best bet would be to have either a custom chip done or maybe just try and get one from a stock 86 ecm for the 350 and put it in the 86 ECM and it should be fine.

 

The donor car didn't have a dyode key for security.

 

If you've got an ECM with an external box, that sounds like a 1985 setup. Check the part# on the ECM, does it end in 870?