fuel Pressure findings.....

[mnmattie]

So I have been hearing some weird noise in the motor (like a loud lifter) under WOT and couldn't pinpoint the sound. well I just added an A/F gauge (had it laying around, put it to use) and found out that I'm leaning out under WOT (yes eventhough it's a narrowband) and thus concluded that the sound is detinition.

Well tonight I just did a fuel pressure reading and at idle with vacuum connected i'm at 30 psi and with the vacuum disconnected i'm at 40 9both right at the bare minimum for spec with Haynes) . but there was no significant difference with how the motor responded when i disconnected the vacuum line to the FPR.

Should I suspect a faulty FPR as being the cause why I'm leaning out at WOT?

-Mattie

 

[wood1]

I'm guessing a stock 91-94 Ex?

Is you engine using any oil, and did you check your lower intake manifold bolts to make sure that they are not loose?

How lean is the gauge showing?

 

[mnmattie]

oops yeah 94

no loss of oil after doing valve cover gaskets...

there is no EGR pipe as the previous owners removed it and put a cap on the manifold. EGR is there so i removed the vacuum line and plugged it until i can get the manifold fixed.

on the autometer A/F, she's reading the last 3 red bars so it's pretty lean. and when i start it up cold and give he a little gas, there is a hesitation.

There is a check engine light on, but it's EGR related since there's nothing reading from the pressure feedback sensor but i wouldn't think that would make me run super lean at WOT.......at least i wouldn't think so

 

[wood1]

Hmmm. Any codes?

 

[MrShorty]

Haynes considers those pressure readings bare minimum spec. I can't find my Haynes manual right now, but Chiltons says spec without vacuum is 35-45 (40 psi is right in the middle of that), and typical manuals I've seen say 28-35 or so at idle with vacuum to the FPR. From what I've seen, I'd say your pressure readings are well within normal. Does the pressure increase above 30 when you goose the throttle (it should in response to the decrease in vacuum)? I don't think fuel pressure is the problem.

Controlling detonation is one of the principle purposes of an EGR system. The computer may be trying to set the mixture expecting the EGR system to be there, and that is causing the computer to be off in the mixture calculations. I'd focus on what is known to be wrong (the EGR system), see if that fixes the problem, then start looking for other possible problems.