I have a '93 Escort with about 155,000 miles on it and have two questions really. The first is a problem i've had since i got the car, at highway speeds or at least at 55mph the car bucks and will lose power till the speed drops under 50 and then picks up again. What would cause this to happen? The other is more recent, i'll be driving and the car will begin to lose power and if you floor it it will rev really hard and slowly speed up, i can usually fix it by putting the car in neutral and rev it to 6,000 rpm's and then put it back into drive. This is an automatic btw. What would cause this to happen?
Lack of power on 1993 Ford Escort
There are many things you need to check to these symptoms. First the condition of the ignition wires and the spark plug boots on the wires. Too high resistance in the wires, splits or holes in the boot will cause the jerking symptom. For the lack of power you need to make sure the fuel pressure and delivery volume are sufficient. Pressure should be between 28-42 psi, volume should be 1liter in about 40 seconds with engine idling. If fuel delivery is ok, you should check ignition coil pack output and current draw, (you will need a meter to test current draw). You can have bad oxygen, Throttle position, Mas Air Flow(MAF) sensors or the sensor grounds maybe poor. If the sensors and grounds are okay, exhaust restriction should be checked. You should pay to have the engine control module scanned for fault trouble codes. Good luck.
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With that many miles on it, you MIGHT look into the Catalytic converter. About 200,000 miles is prime time for those to go bad.