Hi all. I have a 2002 4.2 with 158,000 miles. It has a engine stalling (throttle has no effect, although it will idle roughly) for short periods of time symptom, regardless of load with a random frequency (once a trip to the coast or twice between stop lights, no way to predict). I've done some stuff and many tests but always twisting my evaluations is that my fuel pump pressure tests seem borderline.

I believe my specification is 28-50 psi, I get 28 at idle and a surge just above 30 when accelerating (hand working the throttle in the garage). I get 40 when I pull the vacuum line off the fuel pressure regulator (should be 40-50). I get a steady decrease in pressure as I pump the regulator vacuum up with a hand pump. I get a proportional increase in pressure when I pinch the fuel return line. Five minutes after I've shut down the engine my pressure, oddly, climbs from 28 to as high as 34 psi. One other thing I noticed, although my Haynes manual says nothing about it, is I get just 10 psi when I turn the ignition on (but it starts easily).

My question is about this particular test, not the entire problem . . . that would be a longer discussion. Should I eliminate considering the fuel supply issues since the test is within specifications? Or should I address fuel pump/regulator issues since it is borderline?

I wasn't getting any codes for most of the time period I've had this drive-ability issue but lately, maybe because I spend so much time idling doing tests and scans, I'm either generating or getting a preliminary result P1131 and or P1151, which may be related, along with so many things, to low fuel pressure.

Thanks for any insight you may have to offer.

 

Well, giving up waiting for a response. In my document searches I found 20 psi as a minimum which triggered a trouble code on another 2002 Ford which does have a fuel pressure monitor (mine doesn't). Making many assumptions I'm thinking 28 psi, even though the minimum, is not too much to overcome with fuel trim and all.

When my engine stalls the MAF values go very low (cfm). I did one test drive with the MAF sensor disconnected and had no stalling. Since I've no related codes and the low value snaps in and snaps back to normal I'll investigate the wiring before I buy a sensor. Tested it previously but since it is intermittent I suppose I need to probe and wiggle or something.

Not thinking fuel system any more though.