Transmission normally shifts gears upward the speedometer also malfunctioned

CRANDAL4

MEMBER
2004 FORD TAURUS
V8
FWD
AUTOMATIC
100,900 MILES

Last autumn my car began displaying hesitations/jerks when accelerating at the speeds which the transmission normally shifts gears upward. At the same time, the speedometer also malfunctioned. I took the car in to my dealership, and they replaced the vehicle's speed sensor, as well as the ignition coil assembly (not sure if this is the correct name, but it is the part listed on my work order). All seemed well for about a month, and then the hesitation and jerking began again - intermittently at first and now every time the car is driven. After 3 weeks of the problem reappearing, the speedometer began to malfunction today again.

The speedometer issues make me suspect this recurring problem is electrical in nature, but the jerking/hesitation when accelerating seems to be an issue with the transmission. Any thoughts on what could create both of these problems? Thanks!

1 Reply

JGAROFALO

MECHANIC
489 POSTS

Your problem sounds like the replacement sensor is also failing. A failed/failing sensor will make the transmission shift roughly because without this sensor, the computer has to schedule pressure and shift points based on data from the engine RPMs and input sensor. The speedometer is electronic, and is also driven by the speed sensor. The sensor is close to the exhaust, and could have been damaged by heat if the heat shield had been left off.