1985 Mercury Grand Marquis LS from North America - Comments

24th Jan 2002, 16:21

I have a 1985 Mercury Grand Marquis and also have problems with my car stalling. Can you let me in on the secret?

23rd Apr 2003, 12:44

My 1985 Grand Marquis will not start. The fuel pump shut off switch is not getting power to it. I've looked for the fusible link without luck and the fuel filter, fuses, starter, and battery are all good. Anyone have any comments or know of manuals that would show a better schematic other than Chilton's. Not much luck with their book.

-Brian

28th Jun 2003, 03:39

Hi!

About 10 yrs ago I had an 85 GM LS. What a beauty!! That car an I had many adventures from Chicago to San Antonio. The best cruisers IMHO.

Anyway, I also had the stalling problem you guys are talking about. I fixed mine by replacing the electronic module beneath the distributor. A faulty device is very intermittent, you may loose power while the car is cold or hot. You'll need a special wrench to get it out.

I hope this advise helps you guys.

Omar.

24th Nov 2003, 13:03

Hey everybody. I own a 1985 Grand Marquis LS. I bought it with 19000 miles on it back in 1993. It sat in this guy's back yard. It now has 82000 miles and runs like a champ.

I just wanted to comment on the shutting off while idling thing. Consider the catalytic converters. Mine stopped up. I just replaced the exhaust from front to back duals.

The only problem I keep having after so many years is the climate control sensor in the dash goes bad. When it does, the A/C doesn't work right or the heat won't work. This makes the second one since 1993. A/C blows 39 degrees out the vents. Only drawback is the fuel economy. Mine gets 12-15. Always has. Drive it 60mph or 80mph.

1st Mar 2004, 12:24

I recently acquired a 1986 Grand Marquis, and immediately had the stalling problem. It actually stalled out as I was waving to someone so go figure. But after considering the age of the car, and the 66000 miles, I decided to take a look at the spark plugs, wires, and distributor cap. A combination of those was the cause. The distributor cap and rotor were probably the culprits. It's just a simple tune up, but not having it done is EASILY enough to cause it to stall out. That's my experience with the car anyway, hope it helps.

6th Sep 2010, 07:54

The stalling on the 1983-86 series Mercury Grand Marquis's is really due to the wrong advance on the distributor. Consider changing the timing to a slightly higher idle and advance the timing about 3 degrees from the factory spec.

Also, the comment about the cat converters is correct. They do get stopped up. A little gas treatment solves that problem over time. Using mid-grade fuel will help clean them as well.

I had a 1983 Colony Park and loved it. Right now I am selling a 1985 Grand Marquis Limited edition. In both cases, the idle had to be set as mentioned.

I hope that this helps.

3rd Jun 2014, 21:25

I have an 85 Grand Marquis with the 302 V8. You might want to have your throttle position sensor checked. It is located on the left side of the throttle body as you face the engine. Check to ensure that the wiring is in good shape and not cracked, heat damaged, or broken. A bad TPS can cause serious problems such as stalling, hesitation, and sluggish performance.

Check the air temperature sensor (located on the rear base plate of the throttle assembly). Ensure the plug is clean and firmly seated.

Have a mechanic check your fuel pressure. These vehicles run off electric fuel pumps. Standard pressure needs to be between 34 to 36 PSI. Anything lower can cause poor performance and stalling.

17th Jul 2014, 21:45

I just purchased an '85 two months ago... with 79K miles. Love the car. I was experiencing some stalling... and sudden jerking movements at highway speed. Drove me crazy... I thought it might be tranny-related, but my mechanic said that was fine. I did four things, and I'm not sure which helped, but I have no further issue and it runs like a top now:

1. Replaced the fuel filter.

2. Ran a couple containers of injector cleaner through.

3. Squirted some WD-40 on all the throttle linkages.

4. REALLY tightened down the wing-nut on the filter housing.

I actually think #4 did it. If there are any kind of air leaks, it will cause sputtering, coughing, and stalling here and there.

Hope this helps!

22nd Jul 2014, 04:38

The 302 (and other V8's) will hesitate if there are vacuum leaks.

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