Strange problem with 3400...
 

My daughters 1999 Alero started acting funny a couple of days ago, and I cannot figure it out. Started when, after driving a few miles at 55 mph, would sputter, shake, and not go over 30 mph...she'd hit the brakes and would be fine. Then it went to sputtering, dying, and restarting, before doing it again a few miles later. I drove it yesterday, and after a few miles sputtered, died, took a while to restart, went 500 feet, and did it all over again. Finally got it close to home, it fired back up, and ran fine for a mile, until I got home. Towed it to a friends shop, he idled it for 3 hours waiting for it to do something, but it ran fine. I'm leaning towards the fuel pump going bad, but he said it could also be the ICM going out. I would think if it was the ICM it would act up on idle more so than the fuel pump. Either way my daughter is scared to drive it, and I am at a loss...any ideas out there?

Could be a lot of things..... but if it's the fuel pump, you would have to monitor fuel pressure on the road driving to catch it in the act.

A bad TPS can cause a failure mode that has some of the symptoms you describe. That would probably set a code in the computer (PCM).

I'm trying to remember if a bad transmission solenoid could cause the symptoms. If the car runs fine till it warms up, and seems to "reset" for a short time if you hit the brakes, then possibly.

Scanning the car when it acts up is essential at this point. Could be a bad sensor, connector plug for a sensor, etc. I think a clogged CAT converter could cause it, but I've never had that problem with mine, so I don't know the symptoms that well...

In addition to what AleroB888 wrote, I'm also wondering if there is a bad ground someplace.

I doubt it's the ICM.

When my ICM went bad, all I had to do was touch one spark plug wire and the car stalled instantly, it also misfired a lot and coming home from Michigan I got 41 MPG :eek:

Could try cleaning the MAF. Mine did all sorta funky things before I replaced it. I did get a P0101 code though

Just out of curiosity, when was the fuel filter replaced?

Make any headway on this yet?

The geek way to check your fuel pump is to use an oscilloscope. Normal wave patterns indicates a good pump. Crazy waves = bad.