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Intermittent stall problem with warm engine has progressed to inability to maintain idle after start. At this point I don't have the nerve to take the car down the street (91 9ktCD Auto).
O2 sensor read rich today (.4v -.9) on analog VM as opposed to three days ago when it was .1v-.4v). Plugs are 1k miles old and look normal. Introduced myself to local mechanic referred to me by another Saab owner and he suggested AIC replacement. CPS seems to be reporting as tach bounce is present on crank.
Once started (not easy) I feel the need to save the idle by revving to 2500 RPMs. Sometimes it works and I drop it down to idle. The idle will hold, then die suddenly. Other times I lose control of the throttle as the engine revs and chokes until dead.
My understanding (as limited as it might be) is:
1. The Throttle Position Sensor is an on/off reader that indicates full throttle/not full throttle condition. Should not effect engine start-up or idle.
2. The O2 sensor doesn't have any say until the engine is warm, and if it fails, the ECU will use a default value and not kill the ignition.
3. The Crank Position Sensor sends timing information and rarely fails. If it does, the tach won't bounce during extended start attempts. Mine is bouncing.
4. The intake temperature sensor sends a varying curve of voltage based on temps, but the ECU will substitute a standard value if no signal is present (an unlikely ignition culprit).
5. The Air Mass Meter is a prime suspect as it controls most of the fuel calls before the O2 sensor takes over.
6. The AIC valve/motor doesn't seem to do much more than offer an alternate path for air to the intake when more is needed, but obviously needs to function well to maintain a steady idle.
I've cleaned the throttlebody and the AIC recently and am getting ready to take it to a mechanic for the first time. But first I'd like your input.
My inclination is to get boneyard AMM and AIC, put them in one at a time and see what helps. I may be in denial. but the DI Cassette looks brand new
and I don't think it is the culprit as the engine fires fine when it does run.
posted by 68.198.101...
, Fri, 8 Aug 2003 04:55:57, Fri, 8 Aug 2003 11:25:41
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