Starts up fine then begins to surge up and down. While driving it wants to stall but to keep it going you have to put it to the floor and then it begins to do it again pain in the butt to drive. Replaced fuel pump, replace spark plugs, alternator battery good, and tried another EGR can't figure it out
My car has 100000 miles.
My car has a manual transmission.
This may be a sign of a dirty or failing mass air flow sensor. The mass air flow sensor is a unit in the intake system that monitors air intake as it is mixed with fuel prior to being injected into the motor. When this fails, this can cause an imbalanced air/fuel load to be supplied to the motor which results in an over fueling or under fueling situation depending on the conditions. This is what causes the hesitation or loss of power you describe. This can also cause the engine to struggle to idle for the same reason.
This may also be related to a dirty or failing idle air control valve. The idle air control valve monitors the air intake as it is mixed with fuel prior to being injected into the engine. This valve is controlled by the vehicle's computer which will adjust idle speed based upon other measurements such as engine temperature, intake air temperature and electrical system load or voltage. When you accelerate, the engine RPM increases, and as you let off the gas, the RPM slowly returns to the normal idling speed. This is all done by the idle air control valve. When the engine RPM drops below the normal range of 750-800 RPM (for most cars), this may indicate a dirty or faulty idle air control valve. In cases where this valve is dirty or failing, your vehicle may stall instead of slowing to an idle after the release of the throttle.
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