2000 Duratec misfires

My dad as a 2000 Duratec Taurus with 45K miles. Over the last year, he has had some issues with it misfiring. It was intermittent and unpredictable when it would happen. I think the first time it was just cyl 5. He brought it in and checked out the injectors, pcm etc. They changed the plugs and it seemed to work. The a couple months go by and then cyl 4 did the same thing. He brought it a different place, they did the same thing and it went a way. Now it is cyl 4, 5, and 6. He also had the cat converters on it replaced about a month ago. So obviously the misfire is causing gas to dump into the cats and mess them up. I am thinking it a wiring issues. Ideas?

What about ignition coil?

I think the dealership tried swapping the COPS but it had the same results.

I have a 2003 crown vic police interceptor its showing misfire on 2 4 and 5 . I have changed plugs coils and pcm. Still no results sell it before you spend too much money like I did.

drivebymashing said:

I have a 2003 crown vic police interceptor its showing misfire on 2 4 and 5 . I have changed plugs coils and pcm. Still no results sell it before you spend too much money like I did.

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I spent months chasing an intermittent misfire on my '98 CVPI... Mine was on 8 and 4. I replaced all 8 coils, plugs, all 8 injectors, etc, etc. Sometimes it would run perfect, other times terrible. One odd thing I learned--a failing IAC can actually cause a misfire condition at partial throttle (not just idle). First place you go for a misfire is the ignition system. Then the fuel system. If everything checks out there, it could be a mechanical problem... My car had so many codes and problems when I bought it I hardly knew where to start lol. I eliminated them one by one, but the misfire hung around forever. I finally started to wonder if I had a sticky lash adjuster... Not wanted to pull the heads apart on a car I spent $300 on, I put half a can of Seafoam in the crankcase. Now, normally I'm pretty much opposed to putting anything but oil in there, but it worked...the engine smoothed out and the misfire went away. Well, at least until the oil buildup on the #8 plug brought it back lol.
Anyway, it could be other things too...like an intermittent bad injector connection. Not sure how hard it is to get a NOID light in there, but it will tell you if the injector is getting a signal. Can be used on COPS connectors too. On a side note, from my research into OBDII systems, if the computer detects a misfire on any given cylinder for long enough, it will shut down the injector on that cylinder in order to prevent raw fuel from cooking the converter... If you do repairs on the ignition or fuel system to fix a misfire, it's not a bad idea to disconnect the battery for 10 minutes to clear out the PCM to make sure the computer isn't making adjustments based on old information that included the misfire...