1999 Tahoe MAP Sensor Causing Fast Idle

The 1999 Chevy Tahoe was offered with a 5.7-liter eight-cylinder engine with an automatic transmission and four-wheel-drive for all three trim levels. The MAP sensor relays a voltage signal to the ECM that denominates the amount of vacuum of pressure in the intake manifold. The ECM uses this information in part to adjust engine controls for optimal performance and emissions output. A faulty MAP sensor may relay the wrong voltage to the ECM, causing it to increase idle speed. The MAP sensor on the 5.7-liter is on the left side of the intake manifold directly above the EVAP canister purge solenoid.

Instructions

1

Lift the vehicle hood and support it with the hood prop rod. Disconnect the negative battery cable with the battery wrench.

2

Lift up on the wiring harness tab and pull the wiring harness away from the MAP sensor plug. Lift up on the MAP sensor with a slight rocking motion to remove it from the intake manifold. Do not attempt to pry the MAP sensor out of position, which may damage the intake manifold. Remove the MAP sensor grommet from the intake manifold with the small pick tool.

3

Push the new grommet (included with a new MAP sensor) into the intake manifold hole. Set the MAP sensor into place and gently push down on it to seat it properly.

4

Place a small amount of dielectric grease into the wiring harness plug. Slide the wiring harness into the MAP sensor plug; the tab will click into place when properly installed.

5

Connect the negative battery cable to the battery and tighten the terminal with the battery wrench. Shut the vehicle hood.