1991 Mercury Grand Marquis Stalls

1991 MERCURY MARQUIS
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NK972003
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  • 1 POST
I have a '91 Grand Marquis and when i turn on my car there are 1 or 2 surges in rpm and then it cuts out unless I hit the accelerator immediatly. After that it runs fine until I have to stop at a light or slow down and then it cuts out again. I had this problem before except it only happened when I ran the AC or heat but it would only surge and not cut out. ( by the way AC does not coo if that helps) I had a major tune up about a month ago and put in concentrated fuel treatment but it still happens.
Any help would be great.

Thanks,
Nikki
Dec 10, 2006 at 3:02 PM
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MERLIN2021
  • ✓Experienced Mechanic
  • 17,250 POSTS
surges are caused by vacuum leaks. Get a can of spray gumout, start the car, or have someone else do it and spray around vac hosoes and the corners of the intake manidold, when a change in RPM occurs you are in the right place. 5.0 engines have a problem with the aluminum intakes disolving at the corners! Also were the PCV plugs in at the back , top middle of the intake, the rubber bushing becomes brittle. This cauases oil and air leaks!
Mar 5, 2007 at 10:59 AM

Suggested Repair

With the engine running, spray carburetor cleaner around vacuum hoses and the intake manifold corners; an RPM change indicates the leak. Inspect the aluminum intake corners for erosion and the rear top-center PCV plugs and rubber bushings for brittleness that can cause air and oil leaks.

Conversation Summary

The owner of a 1991 Mercury Grand Marquis 5.0 reports one or two RPM surges at startup, followed by stalling unless the accelerator is applied immediately. It also stalls after slowing or stopping, previously surged only with the climate control on, and the AC does not cool. A recent tune-up and fuel treatment did not help. The expert attributes the surges to vacuum leaks, particularly dissolving aluminum intake corners and brittle PCV bushings.

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