3.8 stalls & surges

[mochie53]

95 Bonne stalls while idling or driving. RPM drops, stumbles,and stalls. Ocassionally will recover and race (3000 RPM) before settling down. After stalling, takes a few trys to get stabilized, each time motor runs longer.
Measured fuel pressure - OK. Problem also occurs with gas cap off.
Removed fuel tank, drained, changed pump & sock + filter. No TROUBLE codes. Also replaced pressure regulator. Occurs with any fuel level or engine thermal condition. When it runs, it runs fine. Manifold vacuum is good.

After stalling, can bleed air out of pressure regulator. Connected a clear hose to regulator return and see a stream of air bubbles. Is this normal ?
Where could air be coming from ?

If air is not the cause, suspect an ignition problem.

Comments appreciated.

[jkinney]

Your pump should flow a fairly good stream of fuel, have you double checked your fuel line connections, and did you put the new pump in, or did someone else? The pump may not have been engaged onto the tube properly. Your getting air from somewhere, and if you follow the fuel lines, you should be able to detect a small leak somewhere if that is the cause. I first suspected the regulator, (returning more fuel to the tank than it should) but you said you replaced it as well.

[mochie53]

I replaced the pump myself. Subsequently got a MAF sensor or ciircuit leaan error. Bought a new one and waited for engine to act up before changing the MAF. No improvement after change. I think this may be a symptom and not the problem. I'm wondering if I have a vacuum leak because the car will intially fire quickly, rev up and stall. Each successuve attempt the engine runs longer until it will settle down to an uneven idle. Can sometimes stall by stepping on the brake. Also replaced plugs, wires and O2 sensor (long overdue) and crank sensor (read numeerous posts about it causing problems). Going to try injector "O" rings next. Mechanic scanned car when its running and components look OK. Thanks.

[Bruski]

Try the fuel pump pressure regulator. I had a problem with stalling and surging with my '99 and that fixed it.