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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.

A: Hi, thanks for writing in. You may have bee...

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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