Engine revving while on park (P) and neutral (N)

1989 NISSAN X-TRAIL
184,619 MILES • 4WD • AUTOMATIC
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WAGALU1234
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I have the t30 engine and it is revving or engine sound is increasing rapidly while moving to park or at neutral after a ride.

I have just replaced my engine head gasket and replaced thermostats, water pump and temperature sensor.

What would be the possible problem or fix for this?

Your kind assistance will be highly appreciated.

Kenny Rapea.
Nov 12, 2017 at 2:48 AM
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HARRY P
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Since this is not a US market car, I do not have any access to specific information about it. Personally, I would bet on a vacuum leak, or intake manifold gasket leak. Also, if it has an idle air control valve, that could be bad as well.

To check the intake manifold gasket (as well as vacuum lines), start the engine. Then simply spray some carburetor cleaner around the intake and vacuum lines. A sudden change in idle speed indicates a leak. https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge - look at this guide, it has some good information too.

To test the idle air control valve, check this guide: https://www.2carpros.com/articles/how-a-idle-air-control-valve-works

Youtube video on testing the IAC valve - https://www.youtube.com/watch?v=GEGItKeg970

Start there and let us know what you find.
Nov 12, 2017 at 9:57 AM