I bought this truck used with a blown 4L80E....I couldnt drive it, so I put alot of $$ into a rebuilt trans, and when I finally got to run it...I found it idled at like 1200 rpms. I found no air leaks anywhere, after much diagnostic work I decided my problem was in the PCM or PROM. I bought an identical 16197427 computer, with a 350 chip in it. It idled, but wouldnt even rev up in park hardly...obviously, underfueling.

So I put my old BMHM prom in the ECU, and it ran the exact same as it originally did...revved in park, but idled at 1200, or slightly lower.

So I contacted TBI chips...they said it probably wasnt the PROM and I did numerous tests, to rule out...again, air leaks. I found none.


So Brian burned me a BMHM chip, stock tune..nothing aftermarket or modified...STOCK. I plugged it in and Voila...Idles at 775-800, goes into gear so smooth.
I take it out to romp on it, and I doscover it has no guts beyond about 2000 rpms, and actually will go slightly beyond 2000, then go below 2000....its trying to rev, but cant.

Truck has no cat, so thats ruled out. New Fuel pump and filter.

So...TPS tests perfect, revs decent in park, has some stumbles off idle, its not smooth....but there is no "dead miss" feel. The plugs, wires, cap, and button are new. Timing is 4* BTDC with the brown wire unplugged.

I cant see a schrader valve to check fuel presure so I mguessing you have to T it in on this setup? Ive got a new FPR on hold at autozone, I figure its just good measure seeing as its probably the 20 year old original on it, and this one appears to be adjustable...or able to be made adjustable...

Any ideas...or did I get a bad chip?