Fuel Pressure

[cobra95]

I have a '95 Cobra with cai, 1 5/8 unequal lenght headers,magnaflow catback exhaust and an adjustable fuel regulator.I just had it dyno'ed and was told it was running relly lean. What should the pressure be set at or am I in need of a custom chip? Thanks for any help. Keith

[Greg@SVTOA]

Keith, why didn't the dyno operator adjust the regulator? How lean is "really lean"?

With a mild setup like you have, you shouldn't be overly lean. If you adjust fuel pressure, the EEC is just going to learn around that adjustment and try to bring the A/F ratio back into the targeted range anyway. Best bet is making more permanent changes like an SCT chip or other means to make A/F and timing adjustments. With N/A combos, lean is mean anyway, so you could lose power by going richer. How do your plugs look?

[SoCal94]

The plugs on our '94 have always looked SUPER lean even back when it was stock. I wouldn't put too much faith in the color of the plugs. Mine are normally whitish grey (vs. 'normal' being a light tan or something).

But I would say that with those mods there's no real reason for it to run super lean unless the adjustable fuel pressure regulator is simply adjusted too low (to where the computer can't even get it to the right AFR by running the injectors with a longer pulse width to compensate for low fuel pressure). But, that situation should generate two DTC's. I think they'll say something like Bank 1 and Bank 2 are too rich, which actually means that the computer reached the rich limit, and the car still measures as running lean by the O2 sensors.

What's the current fuel pressure?

Have you replaced the O2 sensors? They're usually toast by 50k miles, if I remember right. The other thing that would be well bast needing replacing by that mileage would be the fuel filter (which could cause a lean condition).
You could do both as a part of a tuneup and see if things change.

But, it's true that you'll probably make a little less power. It'll be safer/better for the engine though.

SoCal94

[cobra95]

My plugs are whitish grey and the pressure I had set at 40 with the vacuum hose off. I do need to replace my O2 sensors though. I now have 111000 miles on it. I did replace the fuel filter. Thanks for the help! Forgot to check back for any replies!