# Grand Marquis Driving Me Crazy! **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [January 8, 2009, 4:33am UTC](https://community.cartalk.com/t/grand-marquis-driving-me-crazy/24572 "2009-01-08T04:33:46Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![Spookypenguin](https://avatars.discourse-cdn.com/v4/letter/s/b2d939/32.png) [@Spookypenguin](https://community.cartalk.com/u/Spookypenguin)\ **Post date:** [January 8, 2009, 4:33am UTC](https://community.cartalk.com/t/grand-marquis-driving-me-crazy/24572/1 "2009-01-08T04:33:46Z")
1994 Misses/Backfires Okay, to start out I have a 1994 Grand Marquis with 115k that misses/backfires At 100k it had a slight miss when cold so I replaced the plugs/wires with generic autozone set (the miss was a little better) At about 112k I replaced the MAF sensor and the car ran beautifully for about 2 months and now runs horribly, I have already tried another MAF sensor and that is not the problem I have also replaced the air filter, thermostat, and the DPFE sensor (and here is where it gets weird) My car had a December of 1993 build date and I had to use the DPFE sensor from a 1993 since the 1994 was totally different from the one on my car This car misses/sputters/backfires/chugs whenever I put it under load, rather I am accelerating from a stop or accelerating to pass and it doesn’t matter if it’s warm, cold, hot, lukewarm, whatever I am at my wits end, my gas mileage is now terrible and I am afraid to pull into traffic with all of the hesitation/sputtering misfiring…PLEASE HELP! I am at my wits end ---
**Author:** ![hellokit](https://avatars.discourse-cdn.com/v4/letter/h/6a8cbe/32.png) [@hellokit](https://community.cartalk.com/u/hellokit)\ **Post date:** [January 8, 2009, 5:10am UTC](https://community.cartalk.com/t/grand-marquis-driving-me-crazy/24572/2 "2009-01-08T05:10:21Z")
Knowing the trouble codes can help a lot to find what’s wrong. This article should help: [http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c152801e49dc](http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c152801e49dc) ---
**Author:** ![ok4450](https://avatars.discourse-cdn.com/v4/letter/o/e9bcb4/32.png) [@ok4450](https://community.cartalk.com/u/ok4450)\ **Post date:** [January 8, 2009, 5:39am UTC](https://community.cartalk.com/t/grand-marquis-driving-me-crazy/24572/3 "2009-01-08T05:39:57Z")
I agree with Hellokit completely. His advice should be the first step. The only thing I will add is that if you use an analog VOM or simple code reader it would be a good idea to read the directions closely and become familiar with the process first. It’s not difficult at all; just a bit confusing at first if you’ve never done it. (And if you hear the engine RPMs run up during a KEY ON/ENGINE RUNNING test this is entirely normal. They’ll drop back when it’s through testing.) ---
**Author:** ![jrgrimes](https://avatars.discourse-cdn.com/v4/letter/j/c77e96/32.png) [@jrgrimes](https://community.cartalk.com/u/jrgrimes)\ **Post date:** [January 8, 2009, 6:58am UTC](https://community.cartalk.com/t/grand-marquis-driving-me-crazy/24572/4 "2009-01-08T06:58:02Z")
you could have cloged cats ---
**Author:** ![Spookypenguin](https://avatars.discourse-cdn.com/v4/letter/s/b2d939/32.png) [@Spookypenguin](https://community.cartalk.com/u/Spookypenguin)\ **Post date:** [January 8, 2009, 6:03pm UTC](https://community.cartalk.com/t/grand-marquis-driving-me-crazy/24572/5 "2009-01-08T18:03:14Z")
Any way to test the catalytic converters, heat shields are off on one side and half off on the other ---
**Author:** ![ok4450](https://avatars.discourse-cdn.com/v4/letter/o/e9bcb4/32.png) [@ok4450](https://community.cartalk.com/u/ok4450)\ **Post date:** [January 9, 2009, 1:12am UTC](https://community.cartalk.com/t/grand-marquis-driving-me-crazy/24572/6 "2009-01-09T01:12:50Z")
The easiest way to check for clogged cats is with a vacuum gauge. If you’re unsure about the use of a vac. gauge post back and I’ll tell you what to look for. Sometimes the instructions with a new gauge can be misleading or incomplete when testing for this condition. ---
**Author:** ![Caddyman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/caddyman/32/23_2.png) [@Caddyman](https://community.cartalk.com/u/Caddyman)\ **Post date:** [January 9, 2009, 3:06am UTC](https://community.cartalk.com/t/grand-marquis-driving-me-crazy/24572/7 "2009-01-09T03:06:02Z")
All of this miss-firing should cause the CEL (check engine light) to come on…Has the light ever come on?? It sounds like a bad coil. You have two I think, one on the front of each bank of cylinders…other things to check for: Low fuel pressure, EGR valve stuck open when accelerating, dirty injectors… ---
**Author:** ![tardis](https://avatars.discourse-cdn.com/v4/letter/t/f0a364/32.png) [@tardis](https://community.cartalk.com/u/tardis)\ **Post date:** [January 9, 2009, 3:21am UTC](https://community.cartalk.com/t/grand-marquis-driving-me-crazy/24572/8 "2009-01-09T03:21:27Z")
There are two coil packs, each with two coils - four coils total, but only two assemblies to replace. ---
**Author:** ![Spookypenguin](https://avatars.discourse-cdn.com/v4/letter/s/b2d939/32.png) [@Spookypenguin](https://community.cartalk.com/u/Spookypenguin)\ **Post date:** [January 9, 2009, 3:51am UTC](https://community.cartalk.com/t/grand-marquis-driving-me-crazy/24572/9 "2009-01-09T03:51:02Z")
Thanks for the suggestions, I am going to have Autozone run the codes tomorrow, the only code that previously showed up was low voltage to the egr ---
**Author:** ![hellokit](https://avatars.discourse-cdn.com/v4/letter/h/6a8cbe/32.png) [@hellokit](https://community.cartalk.com/u/hellokit)\ **Post date:** [January 9, 2009, 4:43am UTC](https://community.cartalk.com/t/grand-marquis-driving-me-crazy/24572/10 "2009-01-09T04:43:43Z")
Your car has OBD I. Auto Zone may test cars which have OBD II. They, usually, won’t do OBD I. They may have an OBD I Ford tester you can buy; or, you could use the ignition key method of pulling the code (through flashes). Anyhow, bring the codes here for cussin’ and discussin’.