Hesitation on acceleration - Grand Marquis not so Grand any more



Hello everyone,

I have a 93 Murcury Grand Marquis with approximately 120,000 miles on it and recently it started to hesitate on acceleration. Here is the history of the problems and what I have been doing to try and resolve.

For about a year, when you start the car in the morning it would immediately stall. Then when you start it a second time it ran fine. As time progressed I would have to start it two then three times. But once it remained idling for about 15 tto 20 seconds it ran like a champ.

I changed the plugs and that seamed to resolve the starting problem but when I accellerated hard the check engine light woulf come on for a minute then disappear a little while after I leveled out.

I took the car on a trip 200 miles out and back. On the way back it started the hesitation. I would driving approximately 70 miles per hour, coast up on some traffic, when they moved over I had no acceleration. When I came off the highway it was hesitating extremely bad from a stop. It happens frequently but there isn’t a common thread I can find. It happens when it is cold, sometimes, and when it is hot, somethimes.

I went and changed the plugs, wires, fuel filter, and EGR but no luck. I tried to change the gap on the plugs and there is only a slight difference. I tried spraying the coils with a water bottle at night and didn’t see a light show. I guy from the parts store had me run some cleaner through the vacuum hose to try and clean out the intake side.

Some people mention getting the codes by using a paper clip to jump some connections but I cannot find the directions anywhere.

I know that was long winded but I wanted to give you all the facts.

Thank You for all those who took the time to read this and respond.


Niskayuna, NY


That vintage has problems with the EGR passages clogging up. I think that you might be on the right track with that, but the valve might not have been it. You may need to clear the EGR tube and passages out. Do you have some smoke from the exhaust upon idling for a short time? This is common for the valve seals for that vintage 4.6 l. This will also clog up the EGR passages. The other suggestion I have is a new fuel filter lately?

A common Chilton?s or other manual will tell how to jump the pins if that is appropriate for this car. Check your library if you don?t want to invest. I don?t recall when the switch to OBD II came. You might be able to find directions and the blink codes with a web search.

Your stalling may be caused by a faulty IAC (idle air control) valve. The diagnosis is usually IAC if a very little throttle will keep the engine running fine. If not, it is not the IAC.

A very good resource for you is www.crownvic.net. There is lots of knowledge there about these cars.


Change the distributor cap and rotor (if it has them). It’s possible that one, or two, ignition coils are your problem. There are two on your car ($48 each). Here are the instructions on how to test, and change (if need be) the ignition coil(s). Just click on it. http://www.autozone.com/servlet/UiBroker?ForwardPage=az/cds/en_us/0900823d/80/19/2d/88/0900823d80192d88.jsp. To read the trouble codes on some FORDS was a two step process. You would need a voltmeter (with a moving hand) and jumper a connection. The auto parts stores sell a code reader, which simplifiess the procedure, for $30 - $40.


Thank you both for your replies. I just tried changing the ignition coils and the IAC. No luck. I am just about to take it to a mechanic and or start looking for a truck.

I did notice one other symptom that may help the diagnosis. When I stomp on the accellerator, it sounds like it is goinf fast but no surge in speed. I am wondering if it is the fuel pump.