Fuel Pressure/popping on overrun

[tttoon]

Hey, I've been having problems with my m50tu for a couple of months now. The idle is a little rough, the cars smells like a racecar and the exhaust pops pretty hard when shifting down to 2nd or 3rd. I've checked the ignition wires and plugs, changed the dme, checked the o2 and coolant temp sensor, no dice. Since I have only problems with the throttle at idle (I get that impression) I thought I'd check my fuel pressure. With the gauge on the supply side I got 54 psi (3.7 bar, vs. 3 bar factory specified) constantly with engine off. I disconnected the return line and put on another line and the fuel flows out of the valve freely. I tried blowing through the return tube and it is not blocked. So I'm stumped as to why the fuel pressure is at 3.7.

Am I missing something here or are there things I check wrongly?

[jrdeamicis]

But whats your Fuel pressure with it running? What intake are you using? Where is your FPR?

[328ijunkie]

+1 the fuel pressure rated on the regulator is for it under vac at idle IIRC.

[tttoon]

I haven't tested it with the engine on but the Bentley test is with engine off and the fuel pump jumpered, and the pressure specified there is 3.0 bar for an m50. It should then drop to 2.3 bar with the engine running. I'll try that today or tomorrow but with the regulated value already out of spec I'm guessing it'll give similar results. I'm using the standard '95 m50 intake with the FPR on the back of the fuel rail below the wiring harness.