So, to start I have an '88 Fiero, with an L67 (Stock motor) in it.
For the first week or two, mileage was roughly 20-22MPG (Should be seeing 25+ more or less with HWY conditions)
As of the last two weeks, my mileage dropped from 20-22, to 16, to 12MPG.
My LTFT's (Long term fuel trims) have been steading steady when I cruise around -10.9.
They've hit a max of -16.4 (On an unprogrammed ECM) and up to -23 (On a programmed ECM, VATS, DTC codes removed, that's it.)
We've covered 99% of the basics, nobody that does these swaps for a living, can pin point WHY this is happening.
I've taken it to two shops and not even they know.
So, I figured I'd turn to the GPF Community, it may not be a Grand Prix, but it's an L67.
Here are known numbers:
Fuel pressure:
48psi KOEO
40-42psi KOER
50psi KOER, Vacuum disabled.
-Can not smell fuel in the vacuum line.
-No fuel in the oil.
Vacuum is about 17-19psi
(MAP sensor on my Actron is showing around 10inHg at idle, but goes up greatly as I accelerate.)
TPS voltage shows .58v on my Aeroforce (Which died, two weeks of owning it.)
TPS voltage shows .40v on my Actron scanner
TPS Value goes 0-100 smoothly.
IAT * is ~100*
ECT is functioning normally.
O2 sensor is functioning normally.
Fuel pump is brand new, no issues with the pump.
I've tried two different MAF sensors, replaced the o2 sensor, No CAT on the car (Pre-Cat o2 sensor only, Post-cat is neutraled out at .450mv)
I removed the fuel rail and injectors to see if any were peeing with KOEO full pressurized rail. Nada.
Have a MAP sensor on the way.
ANYONE have a clue? LOL.
