Speed Density question
 

A friend of mine recently bought an 88 GT. Car ran really well, but lately he's complaining that the car is running really lean and won't get out of it's own way. Any ideas??? He was thinking O2 sensor, but I thought they usually made the car rich when they went bad.

Help??? P.S. He's a recently converted Chevrolet guy, so I don't want him to get a bad taste in his mouth for Fords already.

Sounds like a weak fuel pump to me or a clogged fuel filter. I would change them both and see what happens.

At wide open throttle, the EEC ignores the O2 sensors, so if your talking about lackluster WOT performance, I agree about fuel delivery. Don't forget the MAP sensor either, but if it is not getting enough vacuum signal and it's good it makes the motor rich, not lean. Could be going bad though.

If the fuel pump sounds good when it cycles when you turn the key on, then I'd change filter first, I guess thats a given.
When my pump went out it just would'nt start one day, and I could'nt hear it cycle(no whining sound like usual), so I checked that it was getting power and knew it was gone. If you can hear it cycle when you turn the key on I'd get a fuel press. guage that hooks to shrader valve first( you can tell if your getting fuel by pressing shrader valve, but be careful it'll spray) before assuming it's the pump and swapping it out. BTW if it is the pump upgrade!!

Thanks for the help! I'll get bowtie boy headed in the right direction. I thought it was a fuel problem, but I couldn't find the float bowls or a Holley black fuel pump ANYWHERE on that car. HA!

Thanks again!