96 e150 5.8L

Fuel pressure at idle is at 30psi. right at the low point.

Can loss of vacuum created by removing the dipstick/oil cap be enough to stall out the engine?

I've been having a nagging p0171 and p0174 code. Most of the time, idle is smooth as butter but occasionally it get a little rough.

Left me stranded twice already and trying to figure out alternative before I have to drop the tank. Changed fuel filter already and maybe think that there is a lot of sediment in the tank or the pump is plugged, failing?

Also, can a faulty EGR or IAC cause these codes and stall out.

TIA for any input.

btw, i did a smoke test which showed no leaks. I watched the mechanic work and he did a thorough job looking everywhere.

Also I have a new MAF, fuel regulator and pcv valve,grommets.

 

When you tested the fuel pressure was the fuel pump fresh or had it been running awhile? It may not drop pressure enough to stall the engine until it gets hot. At 30psi I think its done. It should be at 40+ after the regulator.

 

It was warm. Had just pulled into the shop after driving for about 1 hour. They did the fuel test about 30 minutes after I pulled in.