I have a 1994 Mustang GT, 5.0 liter engine, automatic transmission. It runs well, but it has some kind of strange, sporadic, reoccurring problem - at times the engine rpm will escalate and the transmission suffers as a result - slamming me into another gear or, worse yet, leaving me with little power. It happens after the car is warmed up and has been running a while. I have tried to get service centers to diagnose it for me, but they contend that they don’t see/feel the problem (you sometimes have to drive it a while) or if they do see it, they are not exactly sure what it is and advise I take it somewhere else. I had the transmission rebuilt about 3 years ago. It seemed to help the problem, but it did not go away completely. And now it seems to be back. Does anyone know what this is?
An old friend of mine told me of a similar problem but he had a Dodge Intrepid. It took the Dealer some time to finally figure out that it was the ignition coil causing the whole problem.
The problem might be with a defective Idle Air Control motor. These have been known to go wacky on Fords and cause the engine speed to go out of control.
Had the same problem on my 89GT with 102k but with a manual trans. Check and clean the Mass Airflow Sensor, The Idle Air Controller, and the Throttle Body…problem fixed. Car would start up fine then for no rhyme or reason the RPM’s would jump to 2400and do 70mph in 5th gear by itself.and when it felt like it. If I would kill the engine then restart would be fine for a while then repeat the process. When I pulled the MAF there was a piece of dirt/lint on one of the 2 fine wires. These wires are fragile so be cautious because if you break them its time for a new MAF.
The IAC motor was all carboned up so cleaned that and the throttle body. Its been 3000 miles and no problems. This problem did not trigger the CEL.