Have an at operating temperature condition on an '87 carb'd LX auto where the vehicle will act as though the ignition switch is being shut off and back on in a fraction of a second when the engine reaches a shift point and the vacuum is at peak. Frequently there is a feel of a slight hesitation/stumbling during acceleration The vehicle runs perfect when cold, (under 165 deg), and idles fine at operating temp.

Have replaced a frequency control valve and anti-afterburn valve, (there are a number of these). Removed, cleaned and tested the EGR valve.

Am considering a replacement carb since some symptoms point to a defective power valve/circuit, (not the power piston), and is vacuum controlled.

Any thoughts - Anyone?

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