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What would cause your 1986 Pontiac Fiero 2.5 to jerk driving down the road like it is missing but it idles fine?


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September 13, 2011 5:55PM

If you have an automatic transmission, it is equiped with a "lock-up" torque converter. In normal operation, when you reach about 28-30 mph, the converter goes into lock up. The engine RPM will drop about 200 RPM if you maintain speed above 30 mph. But then a slight change in speed will cause the converter to unlock. Many mechanics solved the problem by disconnecting it. The trade off was a little less fuel milage, but the customer was happy. To test this out, drive at about 35 mph. While your foot is still on the gas touch the brake slightly with your left foot. you should feel the converter come out of lock up.

bad spark plug wires recommend you spray water and listen or if you do it at night you will see the plug wires break down the car will start missing when you spray them down