Questions and Answers

Ford Mustang GT Getting Misfire Codes Q. Vince, I have a 1998 Ford Mustang GT, 4.6 liter V-8 with an automatic transmission. I store the car in the winter months and this spring when I brought it out of storage it runs rough. I've had it out of storage for about two months and have been driving it regularly. When I'm on a flat stretch of road it seems to very obviously jerk at about 35 mph 45 mph and 50 to 55 mph.

As I'm accelerating to get up to the posted speed, the car jerks as though I am shifting, the car is an automatic. Could this be a problem with the transmission. Do you advise to have the transmission flushed as some garages advertise? I've never had it done on any vehicle.

A recent test when connected to a computer said that is was misfiring on 4 and 7. The Ford garage that has serviced the car for five years said that the computer was bad. The Power Control Module, it was replaced. The car continues to run rough.

I appreciate your help.
Tiffany

A. If the PCM says it's Miss-firing on 4 and 7, that is a reliable report.

Since 4 and 7 are on the same coil, I would start looking there for the problem. Wipe the ignition coil towers with a clean cloth dampened with soap and water. Remove any soap film and dry with compressed air. Inspect the ignition coil for cracks, carbon tracking or dirt. What you can also do is swap the coils left and right and if the misfire moves with the coils, then the bad coil is confirmed.

If the problem remains, then it is either bad spark plug wires, bad spark plugs or a bad Crankshaft Position Sensor (CKP) or pulse ring. In addition, it's not uncommon for the wiring from the CKP to the main harness to get damaged.

I do not recommend engine or transmission flushes. They are unnecessary, risky and not recommended by any vehicle manufacturer in the world.