99 Malibu Stalls as low rpm acceleration

[marcuslayton]

Howdy All -

99 2.4 Malibu - 150k miles

Had it into the shop as I wasn't able to find the issue - apparently neither was the shop. Ideas?

Engine cuts on requested acceleration: While in the 500-3000rpm range occasionally depressing the accelerator results in an immediate decrease of engine power – almost like the engine turns off, one can watch the rpm fall – after an intermittent time then surges to an expected acceleration - or will straight stall. Occurs more frequently when engine is fully warm.

And what i think is an associated problem:

Surging during acceleration: While accelerating engine will hesitate at a random rpm (normally from 2000-3000rpm, anything higher is normally consistent) for an intermittent time then surges to an expected rpm. Occurs more frequently when engine is fully warm.

Attempts to corredt it has included:

Fuel injector cleaner
New fuel filter
New spark plugs (boots are only 3 months old)
New air filter
Front o2 sensor
Control Chip

Any ideas? Long time reader - first time poster.

[Speedy_1234]

What About the check engine or the service vehicle soon lights are they on?

[taillight]

Check fuel pressure.

[marcuslayton]

speedy - he checked and there is nothing showing. the only thing that the check engine light has shown for is the o2 sensor - which he replaced

the mecanic did check the fuel pressure and he said came back fine - he all but gave up on it after seeing it twice

:/

[red89vette75601]

I am having the same problem with an 2001 V6. I do not have a service engine light on.
I have replaced :
1 Coil
plug wire
spark plugs
fuel filter

[taillight]

Tape a fuel pressure guage to the window and take it for a ride. when the engine dies, what is the pressure ?

[marcuslayton]

Alrighty - i took it to a different shop. I told him what was up (suspect fule pressue sensor / fuel pump) and this was his response - i didn't even check the fuel pressure - it wouldn't cause your car to act like it wasn't getting anythin and die on you - it would result in a stumble or fail at more regular times.

He ended up looking at the vacum hoses and there was one that needed to be replaced - the one right before the map sensor. There were 2 cracks in it - so i would push the gas - air would be misread / it would read that it had way too much air as it was just coming in from the outside / cut off the air which resulted in nothing but fuel in the engine = engine dies.

Hope that helps you all.

[eewizard]

I have the exact same vehicle and recently had the same problem. The vacuum line (only a couple of inches long) on the map sensor was dry rotted and split just like your vacuum line problem. After I replaced it the car ran great again without stalling anymore. The problem with the vacuum line never caused any codes. Also can be faulty map sensor or idle air control valve. Either of these can be faulty and cause the same type of problems and do not always show codes.