Manifold Pressure Controlled fuel injection system - This sensor works as follows.
Idle - Minimum amount of fuel injected.
Full Throttle - Maximum amounts of fuel injected, as based upon a given RPM.
So, from idle to full throttle, vacuum decreases within intake manifold. High vacuum at idle, and low vacuum at full throttle.
Vacuum hose to this sensor must be fit for duty, and intake manifold must not be sucking extra air in the area where this sensor gets its vacuum. Extra air entering intake manifold where this sensor sucks will increase fuel amounts, which means a richer mixture.
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Auxiliary Air Valve (If equipped) - If one exists on this vehicle, it too must be operational...if it is not closing when reaching 95?F, then a higher idle will exist, unless someone twitched idle adjustment.
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Thermostat time switch - I assume this is hooked to cold start injector. All it does is provide enrichment fuel during cold temps, for some given period of time.
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Saw in the idle-below 1000 rpms - It could be related to fuel/air, electrical, defective engine valve, or uneven compression in all cylinders.
Considerations:
1. See if injector O-rings exist, and renew all of them, after testing them and cold-start spray patterns. Old o-rings tend to allow extra air into intake (I assume injectors are in intake manifold...never seen this setup).
2. Throttle Valve - If its shaft has free-play, it will suck air. All high mileage vehicles will have shaft free-play. A carburetor shop might be able to re-bush, but I would not be concerned at this point.
3. Throttle valve - It must be set to their spec...when done, this may assist in determining what is wrong. If someone has opened it wider, then extra air enters intake chamber, and this will increase fuel enrichment.
4. Throttle valve switch - Adjustment is done after throttle valve is set to spec.
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Needless to say, all vacuum hoses must be fit for duty, and air valve hose's hoses too.
Again, fuel pump pressure must be at spec...if possible, watch fuel pressure when engine is running.