high idle need help please

Asked by Jun 16, 2016 at 11:29 PM about the 1991 Lincoln Mark VII LSC

Question type: Maintenance & Repair

my lincoln has developed a very high idle. starts fairly normal maybe a touch high on idle. as it warms up the idle just keeps climbing. settling at around 3000rpm. i replaced bad ground wire. replaced idle air control valve. replaced map sensor. still rpm is between 1800 rpm as it warms then climbs back to 3000 rpm. now if we disconnect the vacuum line to the map sensor and let it loudly leak air the idle drops to 800 rpm with a rough idle. any clues? i am stumped...

2 Answers

21,485

clean throttle plates, check for codes, iat sensor or maf sensor could be

throttle body has been cleaned thoroughly. iat is from my understanding idle air control valve and it has been replaced with new. my year does not have a mass air flow sensor but it does have a map sensor. it is also new but i am starting to think defective. or it is getting a incorrect signal? what controls the map sensor? if i unplug the vacuum to map sensor it does idle down. but if i unplug the wires while running it dies.

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