High Idle on a 1985 Grand Marquis


Asked by Jan 15, 2017 at 08:48 PM about the 1985 Mercury Grand Marquis

Question type: Maintenance & Repair

So , I just bought a 1985 Grand Marquis from someone and it won't idle down.
I was wondering does anyone happen to know why or has had that problem

3 Answers


Most common cause is vacuum leak, I believe you also have a vacuum advance on the distributor, that can also cause an idle to remain high.

1 of 1 people found this helpful.

Also, check that the automatic choke is opening up. If not, be sure you have power to the choke with the engine running. If you have power to the choke but it's not opening, replace the choke thermostat. If the choke is opening be sure the fast idle can isn't stuck or adjusted wrong. That'll give you a high idle all the time as well. The vacuum advance vacuum hose should be connected to carburetor vacuum, not intake manifold vacuum. There is a difference. Intake manifold vacuum is highest at idle while carburetor vacuum is lowest at idle. HTH. -Jim


*- fast idle CAM. Sorry! -Jim

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