Could a hack engine swap be causing my fuel problems?

[Eriol]

Here's another quick question for teh Supra gurus out there --

In short, I have an '87 Supra with a '91 motor in it. I'm having fuel problems -- it's leaning out at higher RPMS. Could these two be related?

The previous owner did the swap himself. I've talked to him a couple of times, but unfortunately he isn't very forthcoming -- he's still trying to sell me the car, even though I already own it.

I asked him what all he had to do with wiring, and his answer was "Nothing! It was easy. Everything plugged in the same as the old motor." I was under the impression that the wiring was completely different between '87 and '91?

It doesn't look like a hack wiring job, though. I'm just starting to grasp at straws to figure out what's going on, and figured I'd try to find out if the problem could be related to the swap before I drop the gas tank again and start troubleshooting back there.

 

[shaeff]

the swap wouldnt have anything to do with running lean. (the wiring harnesses between 87 and 91 are different, so he must have used an 87-88 wiring harness)

it could be a number of things causing your problem, including, but not limited to:
fuel filter
clogged injectors
clogged pickup screen on the fuel pump
dying fuel pump

what are your mods? we need to know what is done to the car in order to help diagnose it better.

-shaeff

 

[Eriol]

the swap wouldnt have anything to do with running lean. (the wiring harnesses between 87 and 91 are different, so he must have used an 87-88 wiring harness)

it could be a number of things causing your problem, including, but not limited to:
fuel filter
clogged injectors
clogged pickup screen on the fuel pump
dying fuel pump

what are your mods? we need to know what is done to the car in order to help diagnose it better.

-shaeff

No mods yet, other than repairs.

Here's a quick recap:

-New gas tank (old one was filled with rust)
-New (refurbished) fuel pump
-New pump screen, new fuel filter (not Toyota, both from Advance)
-New FPR
-Cleaned & flow-tested fuel injectors
-New O2 sensor

I couldn't accurately check fuel pressure, but my innacurate test showed it to be on the high side of good. I have no way of checking fuel pressure under acceleration, though.

+Fp and chassis ground reads 11.25v at idle and 13.5v under hard acceleration. When I unplugged the fuel pump, jumpered Fp and +B, and measured the voltage at the fuel pump connector, it read 12.25v.

I tried the 12v mod, and my car didn't like it -- would run like crap for about 10 seconds, and then die.

I haven't tried drilling out the J-tube like you suggested, because I'm thinking a restriction in the return line would cause me to run rich, which is the opposite of my problem.

I tested and re-calibrated my TPS this morning, and it checks out.

:dunno:

 

[shaeff]

just out of curiosity... how do you know you're leaning out? do you have a wideband o2?

-shaeff

 

[Eriol]

Nope -- Vf readings, and the conditions of my plugs and old O2 sensor (white glaze after 2,500 and 5,000 miles).

Another member of the Supra community said he'd let me borrow his wideband to verify the Vf readings, but it might be weeks before we have a chance to meet up.