I would look closely for a vacuum leak. When my 88 GL behaved similary,
I discoverd the hose from the crankcase vent tower to the AFM had a hole
in it on the underside where it could not e seen easily. I replaced that
short section of hose and the problem was cured.

Regards,

John Rodgers
88 GL Driver
Rick Koller wrote:

>Greetings All,
>    I have been struggling with diagnosing a high idle/stumble/stalling
>problem all day today..
>Situation: '91 carat automatic, the idle is stuck at about 1300-1500 rpms
>no change from cold to hot engine.
>recent plugs, cap, rotor. Van was running normally. Then suddenly lack of
>power, along with stumbling/stalling and high idle when not moving. Van
>can be driven but at a gradual pace, any heavy gas pedal application
>results in above symptons.
>What have I done:
>I have spare working fuel injection components and in the attempt to fix
>the van quickly, I switched potential trouble parts
>temp sensor II (new),
>idle control module ( tried several that I have including one off my other
>working van)
>idle control valve ( again several )
>throttle position switch, ( cleaned and adjusted the backup that I know
>works )
>switched ECU's
>switched AFM's
>unplugged O2 sensor when the van engine was cold or warm no difference in
>the idle
>checked Hall sensor voltage and it was right at specs ( 5 volts )
>Checked timing and it was in specs 40 degrees BFTDC @ 3000 rpms
>Van starts right up when cold, had some trouble initially restarting it
>when it was hot but this seems to have stopped.
>Any ideas out there? Bad ground somewhere perhaps, don't seem to hear any
>vacuum leaks, have pulled off varios vacuum lines. The one from the fuel
>pressur regulator had some effect of raising rpms.
>Thanks
>Rick Koller
>
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