my car also surges but only when i put the air conditioning on.. 91 z tpi350

Z Speed,

If your car is low on freon the low pressure switch will cause the AC to cycle off, and on. You can feel this when you are driving.

This may not occur while idleing with hood up, so with AC on idle the engine up to about 1500 RPM and see if the AC starts cycling.If it does check the freon.

Larry

thanks larry