Having problems with your Mercury Grand Marquis ?

My check engine light comes on after 70mph and stays on but it only happens when i hit 70mph

Posted / edited by AnonymousUser on : 25-05-2020

Answers :

If the light was flashing when it came on, then it means your engine is misfiring.
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\015\012A solid light can mean anything from a loose/faulty gas cap to a transmission issue.
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\015\012This\015\012light comes on when the computer detects a\015\012fault of some sort in its diagnostic tests. If it keeps detecting this\015\012issue, the light will remain on. If the light turns off, then it has\015\012detected that the issue may no longer be present.
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\015\012In\015\012order to find out what the exact reason was for your light, You need to\015\012have your car computer scanned to retrieve the code that\015\012the computer would have stored when the light triggered. Most garages\015\012will do this free of charge. The code will tell you what may have\015\012caused the light to initially turn on.
I would first tap the ECM codes and see exactly what has been stored. The computer is more than likely reading a high (+) or low (-) vacuum reading at the MAP sensor (manifold absolute pressure). If you have high milage on this vehicle you could pull the sensor and clean with throttle body cleaner. The other possible suspect would be the EGR valve which could be cleaned as well.
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