2003 Crown Vic Misfiring after acceleration

When the vehicle stays in overdrive because the switch on the brake pedal is out of adjustment, at low speed engine is being lugged down and that's why it shakes like that. If your vehicle has an overdrive button to turn it off and on, when your coming to a stop, turn the OD off and see the difference. Get the overdrive switch on the brake lever adjusted or replaced.

The plug wires on this model year and prone to burn through, replace them all, do one at a time and always put them back in the factory wire looms they run through, that is very important, replace any you may break. Use high qyuailty oplug wuires foractory parts are preferred..

Compression check may tell you something.

Idle air control valve. And/or gunked up throttle body, pcv port at throttle where mating to intake manifold.

For this types of problem,there are few help inks to troubleshoot the problem.Click the link below to go through the troubleshooting procedure to resolve the issues :----Idles rough and quits when gas pedal is pressed less? http://technoanswers.blogspot.in/2012/01/1999-ford-f-150-idles-rough-and-quits.html-----------van idles rough? http://howtobyme.blogspot.in/2012/01/2004-ford-freestar-van-idles-rough.html
--------------runs lean and idles rough? http://technoanswers.blogspot.in/2012/02/ford-runs-lean-and-idles-rough.html
-----------Car still runs Rough after tune up? http://howtobyme.blogspot.com/2011/12/car-still-runs-rough-after-tune-up.html
------------Idle flair is noticed on car? Rough idle? car will not idle? Erratic idle speed? http://technoanswers.blogspot.in/2012/02/idle-flair-is-noticed-on-car-rough-idle.html
----------High rpm in neutral? Inconsistant high RPM in neutral? http://technoanswers.blogspot.in/2012/02/high-rpm-in-neutral-inconsistant-high.html
------------Engine Backfires? http://technoanswers.blogspot.in/2012/02/jeep-backfires.html----------- Nissan stalls and bucks on Acceleration?

http://technoanswers.blogspot.in/2012/02/nissan-pathfinder-stalls-and-bucks-on.html

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Nissan Pathfinder Backfires? http://technoanswers.blogspot.in/2012/02/nissan-pathfinder-backfires.html
---------How to adjust rpm? http://schematicsdiagram.blogspot.com/2011/12/how-to-adjust-rpm-on-2009-dodge-charger.html
------------Engine cuts out at 3000 RPM? http://schematicsdiagram.blogspot.com/2011/12/engine-cuts-out-at-3000-rpm.html
----------This will help.Thanks.

running rough means it is misfiring.does it run smoothly without load or at idle?If it does then better check you fuel pressure as the engine needs more fuel under load.

Do you know if the plugs were changed, a bad or broken plug will also cause rough idle and slow acceleration?

i am trying to install an aftermarket temperature guage with capillary tube into my 1988 crown victoria ltd 5.0 efi. where does the capillary tube mount?

change the egr vavle !!!!!!!!

This sounds like a normal condition.What happens is the cold start emission reduction component monitor(software program in the computer) is running.
Cold Start Emission Reduction Component Monitor
The Cold Start Emission Reduction Component Monitor was introduced for the 2006 MY on vehicles that meet the
LEV-II emission standards. The monitor works by validating the operation of the components of the system
required to achieve the cold start emission reduction strategy, namely retarded spark timing and elevated idle
airflow.
When the CSER strategy is enabled, the idle air control system will request a higher idle rpm, elevating engine
airflow. While this CSER elevated airflow is requested, the low airflow test compares the measured idle airflow from
the MAF sensor to the commanded idle airflow from the idle air control strategy.