I need help...my Bonneville keeps stalling. It first started while idling. It acts as if it is running out of gas. Then it started to do it while driving on the highway. I'll be passing a car and it just stalls. It will sometimes start back up but then idles really low and stalls. I have tried to give it gas while this is happening but it doesn't help. After the car sits for about a minute it will start and run fine. It is an intermitent problem, howver it is happening more often in the last few days. I have done a full tune up, the fuel pump and O2 senser was replaced just before I bought the car from my brother-in-law. No engine cades are set either. It is really frustrating me since I know my way around cars. I'm ready to pull the fuel pump out and check for a bare wire or something. I need help fast.

the only thing I can think of is maybe an intake manifold problem, or your removed MAF screen is causing problems.

Mine was doing the same thing. Um... I changed the MAT sensor.... but on your car that would through a code, although it wouldnt show in a SES light. I had slight problems after that but then after cleaning the fuel system very thoroughly with several fuel system cleaners (chevron techron) and buying gas at only conoco and phillips 66 stations it stopped doing it. Maybe your just buying gas at a shitty place?

I have a similar stalling problem... actually, I talked to several folks that have 3800 engines with the same issue. It seems to be very heat related. When the ambient temp gets above 95 degrees, and you're in stop/go traffic, you can almost bet that when you accelerate out, it will hesitate... uneven acceleration. Worst case, just starve for gas. Very similar sensation to the "right turn out-of-gas" problem described elsewhere in this forum. Let it cool down a little, and it will go again, just like nothing ever happened. The dealer "can't reproduce the issue"... read: they don't want to drive it enough to make it act up.

Save your bucks on the fuel pump. Several folks have tried that... no joy.
Fuel filter? no, that'* new
Plugs and wires? no, they are new
MAF screen and throttle body? I doubt it... they look clean
No codes are thrown...

So... I'd like to find the cause of the problem when it happens. Any advise? Hang a fuel pressure guage after the fuel pressure regulator to see there'* a pressure drop? Is there any input or output to the ignition module that could be monitored while driving? How about vacuum? Somewhere I read that the vacuum will fall during acceleration if the CAT convertor is trying to plug up.

Signed... bewildered.

Thanks for the reply. I have monitored the fuel pressure and found that it drops just before the engine stalls. The fuel pump is new, I just replaced the pressure regulator and filter, and blew air through all of the lines to make sure they are clear of obstructions. I then made a small circuit board wired with LED'*. I soldered each LED to a seperate leg on the fuel pump relay. When power is suplied to a leg the LED will light. This allowed me to tell when the computer sent signal to turn the fuel pump on to prime, when the signal left the relay and when ground and power are suplied to the relay. This also allowed me to tell when signal was leaving the relay to run the fuel pump while driving. I was concerned that the low oil switch might be malfunctioning and turning the fuel pump off. This quickly told me that wasn't the case since the relay was receiving power from the computer and the wiring diagram shows it must pass through this switch first. While monitoring the car I could see that the fuel pressure would drop, the car would stall and all circuits where reciving power and signal to run. I then replaced the relay even though I tested it to work properly. This still did not correct the issue.

I then had a revelation...could the aftermarket security system be malfunctioning and cutting the fuel pump off. The system is a Clifford Advant 4. It was already on the car when I bought it and I didn't know anything about it. After some investigation I found the system has a remote wireless fuel pump cut off. This could be malfunctioning and turning my fuel pump off intermittently. This must be between the relay and my fuel pump wiring connector. I am going to trace the wires tonight and see if I can find it and disable it. I'll let you know if I get this issue resolved.

Well, I have completed an expensive experiment.

Driving around with scan tool attached, and monitoring fuel pressure, the stalling problem evidenced as low fuel pressure. No codes. And current still flowing to the fuel pump as expected.

So, we pulled the fuel pump. The pickup screen was sucked in.... and there was a large amount of rust in the tank. I think the tank internal baffle helped to keep the bad stuff pooled around the fuel pickup. The fuel delivery wasn't enough of a problem until the fuel heated up significantly, then a vapor lock condition happened. Stall city.

So, new fuel pump and pickup screen, new fuel filter, and also a new tank...

So far, so good.... no stalling. But we'll see ....

How did you monitor the fuel pressure while driving? I took my tank out and checked the pickup screen. It is new and clean and the pump is new and the fuel filter is new. My stalling happens after I start the car and put it in gear. Then it stalls. It will then stall immediatly agian about three or four times. After that it will then run fine. I did find out though that it will stall while idling if the AC is on and idling for about one minute. After the inital stalling it will not stall agian if the AC is not on.

My alternator puts out 12.75 volts at idle in gear with the lights and AC on. This is not by the guge but by an voltmeter. I do notice the volts come up slow when the car starts and when it stalls the volts never climb past 12. I took the alternator off the car and had it tested at Advance Auto. It rated just over 14 volts. My book shows it should be 14 to 15 volts. I'm not sure if this has anything to do with the stalling. I didn't want to replace it if it is good. The cheapest I found was $90. Maybe someone has more input about the alternators and if their guage also climbs slowly at first.

Thanks for your help. I have to go to China for 10 days for work. I don't think I will be able to get this fixed before the trip. I guess it will still be waiting when I return.