Q: Engine won't rev past 2500 rpm?

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I've checked for leaks, found none, cleaned & replaced MAS sensor, same problem. Replaced throttle body, no change. Replaced, throttle motor relay, no change. What is next?

My car has 175000 miles.
My car has an automatic transmission.

Hi, thanks for writing in. You may have been on the right track with the throttle body. I went down this road with an XK that was going into limp-home mode and not allowing the engine to rev up. In that case, the throttle body was the answer, but it didn’t solve the problem until I disconnected the battery for about thirty seconds, then hooked it back up. The car performs a kind of re-boot where the ECU and the throttle body have a little handshake (you can hear it when you turn on the switch making a little zip,zip sound) and the ECU learns the values of the new throttle body.

Disconnecting the battery is no small thing, you will also have to re-initialize a number of other features, radio code, window motors, possibly the door locks, but doing this re-boot may put you back in business.

Here at YourMechanic, we can have a technician come to your home or office to inspect and diagnose this issue for you, and make or suggest the necessary repairs.

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