20 Most Recent 1985 Mercury Grand Marquis Questions & Answers

Do you have any codes? Did you change an air filter?

I think that over the course of 6 years that the transmission would have changed.

Your alternator is bad that recharge the battery as you drive

You may have a defective turn signal switch, all these circuits run through the switch and on occasion I have repaired a Ford or Two with this same symptom when I was working for a dealer in the middle 80's.

Most likely the switch is bad

Drive it to Autozone or Oreillys and get a free scan of your motor. It can tell you what is wrong and save you money guessing.
It probably needs points and plugs to begin with.
There is a idle control part that works after the engine heats up. It is on the drivers side of the carburetor. It will help to be properly adjusted to prevent stalling. Try these few things and see if they help.

Since you have replaced some of the ignition parts, have you checked fuel pressure and the fuel pump relay ? Do you know what you are loosing when the engine dies ?

Does the fuel pump turn on when you turn your ignition key forward? You should be able to hear the hum of the pump. It will only hum for a second or two. If it does turn on then it is also recomended that the fuel filter be changed because debris gets into the filter when you change the pump.

looks like : And it is mounted on the distributor.

Here'a link to your vacuum diagram Doug.

Some of the vehicles had a Master fusible link close to the battery. When batteries were changed, the link wire could be crushed and instead of breaking the connection, would ground out.Relays. The ignition Relay and other power Relays could stick ON and stay ON when the key is off. Sometimes people clean the dash on their car and the rear window defroster switch is broken and stays on without a light showing that it is on. Bad ignition switches can stay ON despite being turned off.The safest way to do electrical checks is without power and using an Ohmmeter. The Positive and Negative wires are always separate until they connect to do a job. This provides continuity which is an Ohmmeters realm. There are things like your open door Dome light switch, take out the fuse or bulb. Sometimes the radio keeps continuous power for the clock. The PCM may need to be depowered. Once all the constant ON's are depowered, you should be able to hook the Ohmmeter to the 2 removed battery cable ends and have ZERO Ohms on the meter. If you have Ohms, the positive and negative wires are connected somewhere. This is your short.Get a wiring diagram off the Web or your owners manual and sketch your fuse panel. Systematically pull fuses. When the fuse is removed from the short, the Ohms will drop. This means some helper will need to watch the Ohmmeter as fuses are pulled one by one.Match the fuse position to any charts you have, or leave that fuse out and start your vehicle if you can. Anything that does not work is your problem circuit/component.. Then trace that circuit.Hope this is helpful. Its not heavy work. Tiny fuses, methodological, systematic work.

Could be a relay or the ignition module among other things.You will need to troubleshoot it to see if you are dealing with an ignition issue or fuel issue to proceed.

sounds like the cold start fast idle thermostat is defective.