This is a “just curious” question since it’s ultimately someone else’s problem. Drove a rental Ford Focus on a long business trip (190 or so miles one way) recently. Way up, no issues. Way back, noticed a slight but perceptible surging on cruise control.
Approximately 60 miles from home, the car “stalled”. A wrench light came on, the tach read about 2000, and nothing I did gave the car any power. Pulled over, restarted the car, no funny lights.
Figured it was a cruise control glitch and started driving without cruise control. Then noticed the same surging as before. About thirty miles from home, it crapped out again–same symptoms. This time both the wrench symbol and the check engine light came on (check engine did not flash).
Turned off and restarted the car–check engine light stayed on. At this point just wanted to get home. Drove in the slow lane, so I could pull over if it happened again. Sure enough, it did, about 10 miles from home, this time on the upgrade of an overpass near an exit.
Restarted it again, and drove home without further incident, but with the check engine light on the whole way.
So, I’m curious to know what could cause those symptoms on a late model Ford Focus.
Generally speaking, it’s a problem with the throttle-by-wire system. Once the PCM detects a problem, it goes into limited (meaning almost none) power mode. This is a safety feature to make sure the car doesn’t accelerate when you don’t want it to. Either the PCM is getting non-agreeing signals from the redundant pedal position sensors, or the sensor on the throttle valve indicate that it isn’t in the position that it is supposed to be. Sometimes, on some Ford models, this happens because of EMI noise from a defective COP (Coil-On-Plug).
Thanks. I guess that’s better than the infamous Toyota problem. I hope Enterprise fixes this before they send the car back into service.
Scrabbler