Hoping for some help on A/F being too lean on a stock 5.0

[Snakin]

I just had my 94 GT on a dyno and had the A/F tested as well (tailpipe).

Completely stock engine...113000miles

The A/F was way too lean,

3000rpm - 12.5
3800rpm - 12.5
4000rpm - 12.8
4200rpm - 13.1
4600rpm - 13.5
5000rpm - 14.0
5700rpm - 14.0


Help?
Can anyone tell me whats wrong and how to fix it?

Thanks in advance

 

[cobra331]

Filter

Change the fuel filter, if that doesn't do it, put a fuel pressure guage on the fuel rail. If it's low, install an adjustable fuel pressure regulator. You can increase the pressure with one of these. Also, you might try a larger volume fuel pump in the tank.

 

[94CobraPace]

Looks like it not getting enough fuel as the rpm's go higher requireing more fuel. Change the fuel filter, fuel pump could also be going out.
If you want some adjustablilty, you can also get a FRPP extender, which can adjust the air fuel ratio and move the stock rev limiter up. Also takes away the tip in timing retart and 93 mph removal of timing.

 

[Snakin]

Can you give me any more detail on the FRPP Extender, where to buy, how much, a website maybe? Sounds interesting!

 

[94CobraPace]

FRPP does not make the extender any more, so you might get lucky and a dealer might have some left in stock or buy used. I got mine on e-bay and had it modifyed for the Cobra, I see you have a GT, so make sure it has NOT been modifyed for a Cobra. I got mine for $175 & I cannot remember new prices.

I have heard that 94\95 computers compensate for different fuel pressure, to keep the car running at it's desired air fuel ratio.