Engine lagging, help me guys.

[wildcat47]

new to this forum but not to auto forums. hello to all and thanks in advance for your help. i have a 91 lumina with a 3.1, 90k miles. on way to work last week engine was lagging immediately on startup and all the way to work, i could hold 70-80 mph as long as i was on flat ground or downhill and can even acclerate slightly,,,,but car will lag if uphill or med acceleration... if i kicked the pedal hard, engine will go into passing gear and acceleration is fine with no noticible lagging.
i have replaced plugs, wires, fuel filter and ran a quart of seafoam thru engine with no real improvement. i did notice that while i was changing the plugs there was a small bit of fuel accumulation at the throttle body [ noticed it when i took the intake tube off to tilt the engine forwared.
temp sending unit? fuel injector/s? o2 sensor? fuel pressure?

[maxwedge]

Welcome to AF. Lag, means hold back, stumble, misfire?

[wildcat47]

misfire/stalling/chugging.

[wildcat47]

bump

[maxwedge]

Ok, check fuel pressure first, at the rail, about 37 psi, this is done to eliminate fuel delivery issue to the injectors.. After this it should be scanned to look at tps activity, fuel trims and 02 sensor inputs.

[wildcat47]

Thanks, i will try that. i was thinking that i would look at the fuel injectors.

[richtazz]

fuel accumulation at the throttle body would indicate a possible bad fuel pressure regulator. Since your intake plenum and throttle body are air only, fuel may be getting drawn through the vacuum line that goes to the FPR due to a leaky FPR diaphram.

[wildcat47]

Would a fuel pressue check show that the fpr is bad?