Hello everyone i really need your help. I have a 2000 4.6 2wd f 150 ext cab. I started to have a misfire problem on cylinder 8 every so often usually in the mornings or if there was moisture in the air. It gradually got worse over time and when I got it read it had gone to cylinders 5,7, and 8 with the misfire codes which said misfire cylinder whichever primary/secondary circuit misfire and it has now gone to cylinder 2 as well. I replaced all the coils and the plugs with autolite platinum plugs and new coils for this motor and the problem has not changed. It came right back after I cleared the codes does anyone know what possible causes I could check out please this is driving me insane and help is much appreciated!!!!

 

Please list the codes you are seeing?
Good luck.

 

The codes that the scanner brought up were po352 po355 po357 and po358. I assumed that the last number of the code coincided with the cylinder because 352 was cylinder 2, 305 was cylinder 5 and so forth.

 

You not interpreting the code correctly.
This is why you are not solving your issue.
The codes are telling you the harness or the PCM drivers are in trouble, not the coils or plugs.
Check the 'harness' plugup first.
Since the codes are varying it could be the harness or plug connector.
If you see them good then the PCM is suspect.
The way to test is use an ohm meter reading looking back toward the PCM
coil drivers.
You need to see about 10,000 ohms+/- on each coil lead.
No short or opens referenced to ground.
If the PCM is faulty it has to be replaced and programmed along with 2 ignition keys because the coding between the PCM and PATS will not be the same.
Good luck.

 

Ok thank you I wasnt sure what the codes meant but I guess you could see how I thought that and I am by no means an expert thats why I've finally joined this forum. I keep hearing pcm from different sources and was really hoping it wasnt that. Now one other thing...when it started at first it would do this for a few miles and run badly then all the sudden just clear up and run perfectly fine. Then it wouldnt start running bad again until those mornings once in a while or a wet day. Then one day it never cleared up and the engine light would flash everytime I got into it going down the road. Thoughts on this??

 

Also where is the harness or plug connector I need to check located?

 

One other thing that might be important is this was originally a florida truck. I bought it there and drove it there for three months while I was there an no problem and I brought it back to where I live in southern indiana around marengo if you know where that is and it drove fine for months then started acting up

 

It seems like a harness plug issue.
Follow the coil and injector harness back behind the top of the motor on the passenger side and look for a plugup.
It could even be the main PCM plug in the back of the PCM.
That is located low behind the battery area where the PCM projects through the firewall from inside the cab.. A large long connector held in place by a bolt. It has many leads.
Cold temps cause things to shrink and clearances to open up.
Good luck.

 

Thank you for all of your input and help first of all bluegrass 7. Would the connection issue also explain it being constant now though? Even after being driven all day it feels like its running on 4 cylinders I mean it is awful and im still making payments on this stupid thing I dont mean to hate on the truck but I am past the point of fed up with it. Its been a daily driver ever since 6000 miles and its getting ready to rollover the 200k mark and I drove it back from Clearwater florida 1100 miles without a problem and for months after then as soon as fall started coming around with cool temps and moist air this happens I hate to just get rid of the truck but thats the point im at if I dont figure this out soon. Ive been all over this site and there are many that have had these horrendous misfire nightmares and I ask is this thing even worth the headache or the money anymore?

 

I understand your frustration.
Understand that the prolonged use of the truck with these conditions can melt the cat converters under the conditions where un ignited fuel passing to hot converters burns fuel in them.
This can result in temperatures well in excess of 1000 degrees on a prolong basis while running.
The substrate material melts, blocks the flow path, causes loss of power and causes the need to replace the cats at considerable extra cost due to the secondary effects of misfire at the motor.
The relative health of the cats can be looked at with a Scanner at the rear Ox sensor movements in voltage values.
If they get bad enough you will see codes 420/421 indicating they are no longer performing at acceptable level.
At this point it becomes an Emissions issue for inspection.
At this point you may be better off going to a dealer for final repairs or trading up for whatever you can deal.
Aftermarket cats are about $300 per side.
Replacement and labor on a PCM plus programming can get into the $600 plus range depending on the dealer charges.
Just to give you a feel for the possible repairs.
Hope is that you find a harness issue and everything else is still good.
I can't help you any further from this point.
Good luck.