Stalls right after start up?

[lazer2463]

I have a 2004 GP 3800 that runs great other than it only stalls sometimes immediately after start up. Then just restart and press on the accelerator a little and it idles and runs fine. No problems other than that. Just put new plugs in and ran injector cleaner through fuel system twice.

Any ideas?

[CrazyHorst]

"A" possibility is...that the engine is not overfueling at startup like it should. Essentially the "cold metal" has a bad tendency to condense fuel vapors and allow the air-fuel ratio to go lean that can cause a stall.

The startup timer is a lookup-table based on intake air temp and engine coolant temp. Possibly one or more of those sensors is giving an erroneous reading.

Another possibility is that if you have an ETC "electronic throttle control" there is no IAC "idle air control" pintle. I don't know what the content is for 2004 Model Year. However one of the above is responsible for controlling air flow at idle and has a strategy to open rapidly as a "stall-saver". If either the throttle body or the IAC port gets coked up by PCV vapors (sometimes flow out ahead of the throttle plate if there is enough crankcase blowby usually in high rpm escapades) then this can profoundly affect the ability to control idle.

In the "right-after-startup" moment in time I suspect the ETC or IAC is quite active trying to get the engine started and quickly manage airflow so there is not a big overshoot or rpm "flare" and so it is probably sensitive to disturbances or any sticking.

If an ETC is used, I think it is a pretty "dumb" device other than gross failures. There is also a little extra engineering in there because of the safety-nature of the device and its affect on being able to control those 2-ton missiles.

[coolzzy]

extremly common problem with the newer gen of grand prix. Easy fix, you need to clean your throttle body/plate. you can remove it to do this, or clean it on the car. undo the clamp on the rubber hose that comes off your air cleaner box and connects to the top of the engine. Look inside and you will see a goldish circular butterfly. Use a screwdriver or similiar to push it open and hold it that way. Spray some carb cleaner and use a rag to clean all the black soot from the sides/top/bottom of the tube in which the valve sits. You can also clean it from the valve. Reassemble and voila, problem solved. I go my car for a steal cause the dealer thought it had engine problems, $2 can of carb cleaner later and all fixed.

[tblake]

I agree, give the throttle body a good cleaning. Make sure and use a new gasket when you put it back together or you will have a vacuum leak.

[BNaylor]

Originally Posted by CrazyHorst

If an ETC is used, I think it is a pretty "dumb" device other than gross failures. There is also a little extra engineering in there because of the safety-nature of the device and its affect on being able to control those 2-ton missiles.

If an ETC is used? The '04 and up use the "drive by wire" electronic throttle control system which is actually very reliable. What gross failures?

[doctorhrdware]

Remember the Air bus airplane that crashed. It had the same system as the drive by wire, but it is fly by wire. There was a backup which has the connections to the control surfaces. But both systems failed causing the plane to dive nose first into ocean.

[CrazyHorst]

I am saying the ETC is very reliable. However the potential exists for something screwy to happen by a condition far from normal, and it to get energized to WOT without intent or control of the user. Same thing could happen with a cable-throttle too...the cable could bind at WOT where it wouldn't release but the potential is remote.

I think there is some double redundancy (could be triple) to make sure that doesn't happen.

[lazer2463]

Thanks guys, I'll try cleaning the butterfly first and go from there.

[lazer2463]

Thanks Guys, so far so good on the starting......