Car Problem Reports

Mercury Grand Marquis Problem With Idle Air Bypass Valve May Cause Engine Performance Problems

Mercury Grand Marquis Problem
9 Reports
Me Too

Model Years Affected: 1990, 1991, 1999, 2000

Average Mileage: 119,525 mi (75,000 mi - 151,100 mi)


If you experience difficulty starting the engine when cold, stalling at idle, or hesitations during acceleration, it may be the idle air bypass valve. This valve helps the vehicle idle steady when the accelerator pedal is not pressed.

  •  Rookie

    it starts up and than it shuts off but starts back up. can anyone help me with this problem.

    Flag This
  • Visitor, , 103,000 mi

    Engine turns over, but cuts off when I put it into gear. I have to sit with my foot on the gas pedal to keep it going. Usually, after 10-15 minutes - and several attempts - it will continue running when I take my foot off the gas pedal...then, I can go and it will keep running. Once in a while (1 in every 10-15 times) when I start it, it will immediately just run like it's supposed to.

    Flag This
  •  Rookie

    When accelerating between 1st and 2nd gear, there is a lengthy shift time, also I notice when pressing slightly harder on gas pedal while already in travel, it is not responsive as a v-8 should be with quick acceleration. It seems as either gas is not traveling through the gas pump at the required rate, or after getting my intake replaced, that possibly one of the (pistons/cylinders) could be bad, or may have a compression leak. No smoke or stalls and no problems starting when cold. Thanks!

    Flag This
  • Visitor, , 151,100 mi

    Cold starts difficult (long crank and had to throttle engine to keep idle going.)

    Flag This
Ask a Question