Loss of acceleration on 1997 Geo Metro

Recently, my Geo has a tendency to loose acceleration at around 65 mph and doesn't pick back up until around 50-55. Motor doesn't stall but I depress accelerator and nothing happens. Is doing same thing when I let off accelerater suddenly and try and depress again; no acceleration until around 30-40 mph. What is causing this?

Asked by for the 1997 Geo Metro
THROTTLE POSITION SENSOR. I had the same problem on a 1998 chevrolet S-10
2 answers 5 comments
Is your car manual transmission or automatic? If it is manual transmission I wonder could the clutch be slipping. More likely a loss of power at higher speed particularly if you are driving on a long flat road and have the accelerator pressed down hard, if the car gradually looses power or flat out looses power its probably fuel starvation ( a blocked fuel filter or failing fuel pump). If a car looses power and gets jerky as you accelerate it could be a bad plug wire or other ignition fault. Hard to guess with out experiencing the problem first hand.
It is an automatic. Looses power suddenly but engine does not quit running. As if transmission is shifted into neutral but even engine won't 'rev-up' when accelerater is depressed.
If engine won't rev up when shifted into neutral, I would shy away from blaming the transmission and look at fuel loss or something switching off. If the computer looses an input signal it doesn't make accurate calculations for fuel and ignition spark controls, so you could have an electrical problem. Does the check engine light come on? I would plug in a scan tool and see if there are any stored trouble codes.
What do you do to get the car to run/drive normally again?
I have to allow vehicle to slow to around 30-40 mph before it picks back up again. I figure that if the problem is fuel filter block or fuel pump going out, the engine itself would either sputter and/ or die. The engine itself doesn't die at that point, just no pick-up until vehicle slows to between 30-40 mph no matter what I do. I never shift INTO neutral while driving but engine acts as if it is in neutral ie: NO acceleration.
I'd like to know what you find out to be the problem. Your car has OBD2 diagnostics it holds information in the computer if it sees a problem related to emissions or performance and a good scan tool allows you to read live sensor data as your drive. I would like to see air flow intake figures, whether the scantool sees engine RPM (ignition signal) when the car looses performance. Plugging in a scan tool and driving while the car mis-behaves is probably going to be the way to go.
Thank-you so very much for your imput! It is greatly appreciated.