1990 Buick Century, idle but won't accelerate

Help, me & my Mechanic (35 + yrs. exp.) stumped. :banghead:
1990 Buick Century w/3300 V6, fuel injection, less than 80,000 miles
Veh. may have had 200 miles p/yr put on it last 3 - 4 yrs.
Was still regularly serviced.
No previous problems no fluid leaks, clean motor.
Hessitated on hwy twice, wouldn't start after second hesitation, but did later & ran good. Wouldn't start for about 15 mins. after fueling once, but ran good when did start, had fuel pressure at sharder valve both times. Next trip after about 10 miles, started loosing power, finially quit, NO pressure at sharder valve. Towed in. Mechanic said ECM bad, changed it, ran idle, but would not accelerate, chk'd everything. Put different ECM in, same thing, idle, but won't accelerate, has chk'd fuel pressure, fuel regulator, ICM, CPS, everything can think of :sly: .
***CAN ANYBODY GIVE US AN IDEA OR SOMETHING YOU MAY HAVE RAN UP ON THAT WE HAVE MISSED, :runaround: FAST, PLEASE HELP ANYBODY???***

Help, me & my Mechanic (35 + yrs. exp.) stumped. :banghead:
1990 Buick Century w/3300 V6, fuel injection, less than 80,000 miles
Veh. may have had 200 miles p/yr put on it last 3 - 4 yrs.
Was still regularly serviced.
No previous problems no fluid leaks, clean motor.
Hessitated on hwy twice, wouldn't start after second hesitation, but did later & ran good. Wouldn't start for about 15 mins. after fueling once, but ran good when did start, had fuel pressure at sharder valve both times. Next trip after about 10 miles, started loosing power, finially quit, NO pressure at sharder valve. Towed in. Mechanic said ECM bad, changed it, ran idle, but would not accelerate, chk'd everything. Put different ECM in, same thing, idle, but won't accelerate, has chk'd fuel pressure, fuel regulator, ICM, CPS, everything can think of :sly: .
***CAN ANYBODY GIVE US AN IDEA OR SOMETHING YOU MAY HAVE RAN UP ON THAT WE HAVE MISSED, :runaround: FAST, PLEASE HELP ANYBODY???***

I don't see any fuel pressure numbers here, should be 40-47psi key on eng off. When was the fuel filter replaced last? It may be plugged.

When the vehicle won't start, that's when it's easy to diagnose....

As GMTech1 said, what is the actual fuel pressure and last time fuel filter was replaced? When the car won't start, will it start and run with carb cleaner sprayed into the intake?

Has the vehicle been scanned for codes?

If you have a MAF sensor, disconnect it and see if the vehicle starts....

Driving only a couple hundred miles a year, pull a plug and check if it is fouled....

How does your mechanic equate no fuel press. with a faulty pcm?

Ok, I may have written a confusing meassge, so let me shorten it.

I was the one that it quit on. It was running great before it quit on me.

When it quit, I had pressed the valve in on shrader valve & no fuel came out, was not any pressure there at the time it quit on me, but could hear fuel pump running. Had it towed in.

As of Friday 7/26, mech had changed fuel filter, but said ECM was bad, has tried 2 ECM's, he has car cranking & would idle, but will not accelerate. As I said he is an exp. mech. & he says he has checked everything like CPS, fuel pressure, & all.

I believe him, but we know sometimes that even the simplest thing can be over looked or could be something he hasn't ran up on before that somebody else has.

So if car will idle but won't accelerate, fuel pressure is good, everything tests good, what would be most likely to test wrong or what else could it possibly be that either of you guys would re-check or next step you would take?

Back pressure.....

Seen the ign module on those cars also cause these symptoms.

Seen the ign module on those cars also cause these symptoms.

K, he told me Tue. morn., that it had started idling rough again. As rechecking things, he said he put noid back on & getting weak light on all injectors. Gonna try a couple of more thing later in the day, but kinda leaning towards ICM now after some of the things I have learned last few days, especially about the ICM on that motor. Thanks

Back pressure.....

On exaust system ?

Yes.....