Is your surge a stutter (drop) or a rise in RPM, what does tach say?

Is it steady (jumps from one level to another and stays there) or is it jumpy (RPMs are sputtery in the new range)?

How long does a surge last if you touch nothing?

Do you have a functioning engine idle control knob to raise idle up/down? (try it).

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Cheers!
Scott McPhee

1987 300D