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Mercury Grand Marquis Repair Questions and Answers

Question:  1996 Mercury Grand Marquis mileage: 162,000. I have recently replaced all of the oxygen sensors, fuel pump, fuel filter and fuel regulator and the car still has no acceleration power on the highway.  I also discovered the reset button is stuck on the emergency fuel shut off switch located in the left side of my trunk.  I need to know if it is possible to bypass or disconnect this shut off switch and if so, how.  If this is not possible, where can I purchase a new switch?  I live in Fargo, ND.  I look forward to hearing from you.  Thank you in advance for your time and your cooperation 

Answer:  Your lack of acceleration is probably caused by a partially plugged catalytic converter not the switch.  As for the fuel cutoff switch you mentioned its function is to stop the fuel pump if an accident occurs.  Obviously this switch should never be disconnected or bypassed.  If you feel it is “stuck,” the part is available from the manufacturer of your vehicle. 

Question: 1990 Mercury Grand Marquis  mileage: 90,000. This is my head-ach. It started one day when I passed a car and the engine started to miss. I tested the spark and the #2 cyl had no spark. I then tested for spark at the cap to eliminate the plug and wire and had no spark coming out of the #2 tower, but if I raise the throttle, it will get a very weak spark. Just to let you know I have replaced cap, rotor, coil, module and pick-up. The real problem is if I shut the engine off and restart the miss goes away and I can make it miss again by flooring it under a load. When the miss is there it's always #2 no spark and with the spark tester on #2 I can get it to spark by unplugging the timing spout connector and when I plug it back in it will lose spark again. If I leave the spout connector out it won't miss or with spout in and restart engine as long as I don't floor it under a load. I bought a wire diagram book from Ford factory and the circuit# is 324 which is a yellow with light green stripe. It goes from TIF module to the spout and from the spout to pin 36 at the EEC module. Pin #36 on the EEC description says transmission overdrive switch to heat module. I don't know what the heat module is and 324 circuit seems to end at the EEC. I was wondering if it is part of the EEC and if the EEC is what is bad?

Answer: You have a strange problem. The only thing we can think of in view of the testing you have done would be to try replacing the EEC with a known good unit.

Question: 1990 Mercury Grand Marquis GS  mileage: 91,000. When air-conditioner is on and the car is running at 60 MPH, the air-conditioner blows very cold. In traffic with stop and go it starts blowing hot. Have replaced compressor, clutch, dryer, condenser and also installed inline filter. When in traffic, temperature gauge climbs and then the air-conditioner will blow hot. Is there a limitor switch or something that cuts the air-conditioner out when the temperature gauge gets to a certain point? Any ides of how I can fix the problem. I live in AZ and it's very hot here.

Answer: Check the cooling system, particularly the radiator to make sure it is not partially plugged. Additionally, check the radiator fan for proper operation. If the engine temperature is running way above normal, some of the heat is transferred to the air-conditioning condenser, which causes the air-conditioner to lose efficiency. As for your question about a "limitor" switch, there is a high-pressure switch in the air-conditioning system that cuts the compressor out when the pressure gets too high.

Question: 1995 Mercury Grand Marquis  mileage: 124,000   ABS system activates below 45mph with no warning lights and no error codes. Dealer could find no problem with sensors or sensor rings. Ford TSB says to check for poor or corroded connections which dealer says can take several hours of trial and error to track down. I know that one or both of the front rotors is warped, could this cause one of the sensors to give a false output at lower speeds? I am not convinced about the poor connection theory as that usually leads to erratic or sporadic problems and this problem seems to be speed related.

Answer:  You may have a faulty ABS computer. We would obtain a known good computer and substitute it for the one in the car first to eliminate the computer factor. If the computer proves not to be the problem, the connectors would need to be checked for corrosion or high resistance. Warped routers would not cause the problem you described.

Question: 1996 Mercury Grand Marquis mileage: 42,000. Every several hundred miles or so (between code clearing), the check engine light will come on. The codes are 0171 and 0174 indicating a lean condition. Gas mileage is also down about 10%. I have replaced the fuel filter, fuel pressure regulator (fuel pressure is 31 psi with vacuum and 42 psi without) and EGR valve. I have also tuned the car replacing plugs, plug wires and air filter. Any ideas as to what is triggering the codes?

Answer: Try replacing the oxygen sensors.

Question:  1997 Mercury Grand Marquis 4.6 liter mileage: 48,000.  When replacing the engine coolant as suggested by the owners manual at 48000 miles, I simply drain the old coolant from the bottom plug from the radiator then add new coolant into radiator.  How much coolant and how much water should I add?

Answer:  The coolant to water ratio should be a mixture of 50% coolant and 50% water.

Question:  1984 Mercury Grand Marquis mileage: 150,000.  Refresh my memory a bit; forgot how to check if my alternator itself is ok.  Alternator currently in vehicle was rebuilt and boosted to 100 amps instead of the normal 65-70-amp type.  Your response would be greatly appreciated.  Thank you.

Answer:  Assuming the battery in your car is in good condition, you can check the alternator by having the engine on a fast idle with the headlights and the air-conditioner on.  The voltage across the battery should be 14 to 14 ½ volts.  Double check to see that the alternator belt is tensioned properly and in good condition.

Question:  1995 Mercury Grand Marquis  mileage: 75,000.  The hazard flasher and directional signal stop working. My owners guide tells me it is in the fuse box under the dashboard, but it is not.  Could you tell me where it is located?  Thank you

Answer:  Both components are on the passenger compartment fuse block located behind the left side of the dash.  It is tucked up under the dash so that it will not be kicked.

Question:  1987 Mercury Grand Marquis  mileage: 132,000.  I cannot pass emissions testing.  I first brought my car in and failed on HC and CO.  About a week later I tried again burning premium fuel and after adding some emission system cleaner.  I was still high on CO and HC.  So then, I changed the air filter spark plugs and ignition wires.  I then went back and tested again.  I added some rubbing alcohol to my fuel tank to try to get it to burn a bit cleaner.  My CO and HC jumped about 50% each.  I do not want to sink too much money into this car.  What should I do?  Oxygen Sensor?  Get the computer checked?

Answer:  After reading your question and test results, we would suggest installing a new catalytic converter, as we doubt yours in working properly.

Question:  1985 Mercury Grand Marquis  mileage: 136,000.  My heater starts to blow out hot air then after 20 minutes of use it all of a sudden changes to cool air.  Selecting different setting does not change the temperature except I can select and get very cold air.   This cool air stays that way until I shut the car off and restart it (the car) when it is cold.  Is there a temperature sensor that could shut this down?  Is there any relationship with this and the thermostat?  I suspect the valve that directs the flow of hot water is changing its settings but from what cause I’m not sure hope this is enough info.........I just bought the car and the previous owner replaced the air conditioning system (hoses, evaporator, seals)...I’m not used to cars with the integrated climate controls.

Answer:   It has been our experience that the system you have was poorly designed, functioning as it was designed – it is just the nature of the beast.  There is really not much you can do other than wearing a jacket and gloves on cold days.  You can try getting the system into the warm mode and then unplugging the fuse that controls the automatic system.

Answer:  Sounds like your stalling problems are probably caused by the carburetor flooding.  A carburetor looks like it is in order here.  Also, have a new float installed when the carburetor is apart.  

Question:  1995 Mercury Grand Marquis mileage: 145,000.  I had the Pittman Arm on my 1995 Mercury Grand marquis replaced.  After it was replaced, the car drifted to the left and the steering wheel was aligned in this position.  When I took it back to the dealership and told them that it was not like that before and they told me that changing the Pittman Arm would not create an alignment problem.   Therefore, they aligned the car.  Now it seems that I have a problem keeping the car straight.   I am continuously adjusting the steering wheel to keep the car straight.  As I drive down the interstate, all of a sudden, the car will go to the left or right which is somewhat scary.  Could an improperly installed Pittman Arm create this situation?  I have been told there is something called memory steer, could this also be the problem.  Thank you for your assistance.

Answer:    The problem you describe is probably caused by something in the steering lineage that is binding.  Locate and repair the binding component and that should fix your problem.

Question:  1973 Mercury Marquis mileage: 150,000.  My son and I rebuilt the C6 transmission.  Now we have reverse and no forward at all.  We checked the governor and replaced the vacuum shift module.  In addition, made sure the linkage was shifting the valve.   We even pulled the transmission and took it apart and put it back together again to made sure that we had not put something together wrong.  Everything is exactly as the manual said it should be.  HELP! Thank you for your help

Answer:  At this point, we are only guessing.  You might try adjusting the bands or you may have a sprag in backwards.

Question:  1995 Mercury Grand Marquis  mileage: 75,000.  Check engine light code 332? The EGR valve not opening.  Had this problem on another Mercury Marquis and dealer cleaned EGR with spray without removing and changed vacuum regulator.  How can I tell if it is the vacuum regulator or carbon blocking the EGR valve?

Answer:    The EGR valve is controlled by the vacuum control motor.  It has been the “weak link” in this system.  Check the EGR valve to see if it is plugged by manually raising the EGR valve with the engine idling.  If it is not plugged, raising the valve should almost kill the engine.

Question: 1984 Mercury Grand Marquis  mileage: 60,000.  My 72 year-old dad has tried for 2 weeks to remove the heater core from this car.   He has taken everything loose that he thought would do it, but is now stumped.  He says about all that is left is the rivets!  He's pretty sharp and this is the first time I have seen something really stump him!  He seems to think maybe there is something he's not seeing that needs to come loose.

Answer:  The rivets should not have to be removed to get access to the heater core.  However, if all the bolts are out, maybe the heater-duct is stuck on the rubber seal; that sometimes happens.

Question:  1984 Mercury Grand Marquis  mileage: 85,000.  My problem is the car stalls when you stop or slow down.  Any suggestions would be helpful.

Answer: If a major tune-up has not been done recently, this could be the cause of your problem.  Replace the spark plugs, plug wires, fuel and air filters, etc.   Also, replace the oxygen sensor.  In addition, service the fuel injection system.  Clean the carbon deposits from the throttle bore and idle passages.

Question:  1987 Mercury Grand Marquise mileage: 154,000.  Within the past 6 months, the car has had a stalling problem and rough Idle.   Than a month ago, it stalled and would start.   Try to jump it, wouldn't take a jump.  Had it hauled off to the garage.  They put a new battery in, did some adjusting to the Idle.  It work for a few days, Than it starting stalling again but, not bad, but, progress to worsen over the month to the point it would stall over and over again before catching. Once moving it wouldn't stall, unless it was in park. Took it back to the garage. This time they put a new throttle sensor or something on that line.   I picked up today, drove it for five minutes seem to be driving well, stop at a store.  Got back in and it wouldn't start.  Jump it, started up, shut off, no start.  Could there be a short somewhere, or starter.  We had a probable with one of the electric windows this past summer, couldn't get to come up.   Moved the wirer in the inside panel, window went up.  Could this be the problem?

Answer:   Here are some things to check.  Load test the battery.  Check that the battery cable connections are clean.  Check for 12 volts to starter solenoid with the key in the start position.   These things should be checked first then the ignition switch, starter and starter solenoid.  One of these may be faulty.  Also, check charging system.  Here is the procedure we use to isolate a battery drain.  Remove negative battery cable from the battery.  Using a 12-volt test light, hook one end to the negative battery post the other end to the negative battery cable you just disconnected.  The test light will glow or “light” if there is a drain.  If the “light or glow” is faint, that is probably normal draw for the clock or computer.  If the “light or glow” is bright, then there is a large drain.  That should be corrected.  Now start removing and replacing the fuses one by one until the light goes out; that one will be the circuit with the drain.  Remember to hold in the button in the door jam for the interior lights.

Question:  1990 Mercury Marquis  mileage: 160,000. Heat is on/off at no regular timing heater fan is in High and switch has no control of fan speed-- climate control--a/c-- have replaced thermostat, inline heat control on upper radiator hose, and heat sensor on intake manifold. Replaced water pump as well. Any advice?

Answer: Your solid-state fan speed control module may need replacing.

Question:  1990 Mercury grand Marquis mileage: 98,000. When riding in the car there is an odor of gasoline. The odor is worst when idling at a red light. Maybe the fuel pump is about to die?

Answer:  Get your car inspected immediately. Leaking gasoline is an extreme fire hazard. Especially have the seals on the fuel injectors checked.

Question:  1983 Mercury Marquis, 150,000 miles. Ignition Problem? Car will cut off for no apparent reason. We installed a new ignition coil. We loose our 12 Volts to our coil every now and then. We loose our ground occasionally. We think the problem is either the ignition switch or the main computer. It does this either hot or cold going down the road or sitting still. Thanks for your help.

Answer:  It is likely you have an ignition module going bad. Our second guess would be the ignition switch.

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