2000 v8 3.9 with P0420 code and more need help!!

v8mustang289v8mustang289 Member Posts: 2
I have 3 codes total. P0420: Bank 1 Cat Efficiency Low, P0307: Multiple Cylinder Misfire and P1285: Cylinder Head Over Temp.
I hade a coil go out.. no supprise, and didnt fix it right away. I then had a second coil go out so I had them both replaced as well as the plugs. They were cylinders #5 & #7. Replacing these did not solve the misfire. Upon further inspection taking the coils back off i have found that the plugs are not firing at all. What could be causing this? Could it be a timing sensor? how do i test for that?


  • akirbyakirby Member Posts: 8,062
    I think you probably have other COPs that are bad and driving it with the misfire ruined the catalytic converter. I would replace all of the COPs, check for leaky valve cover gaskets and then recheck the converter. Might as well change the fuel filter as well. The other possibility is a bad fuel pump.
  • chollybchollyb Member Posts: 5
    If I'm not mistaken, the cylinder number designations changed after 2000. If you are using the newer arrangement as your guide, you may actually be changing the wrong COP's (I know you didn't wanna hear that). I think that #5 and #7 by the old way are actually #6 and #8 now... You can check with your dealer to find out.
  • cfrey81cfrey81 Member Posts: 2
    I too have '00 V8. I have had that 420 code being thrown since I pretty much got the car in '05. Comes and goes...never really had issues relating to that as far as i know. BUT, in past few months been having bad misfiring as well, only threw a code for cylinder 2 but it has gotten BAD now and just cant afford a dealership fix this time. I changed the egr valve being that it was cheep and easy to fix, also I have almost 210K on my car. I bought it with 38K. It runs better but still misfires, just not as bad. I have plugs and 1 cop, but would rather wait to see if the problem will pan out being that the car has a "learning" curve with the driver.... You can look for hairline cracks in the sealant on top of the cops, moisture can get in there and fry the cop. Not too much advice here cuz I usually take to dealer, but not this time... Have you fixed the problem yet tho? I JUST changed my egr valve about 2 hrs ago. Let us all bow our heads and pray :D
  • v8mustang289v8mustang289 Member Posts: 2
    I tore into the front end of the engine and found that a tensioner on the larger timing belt on the drivers side was broke, replaced it and that helped a bit but since the timing chain is stretched it didn't fix it completely. But at least o now know what the problem is!
  • blazinbyeblazinbye Member Posts: 1
    My son has a 2000 3.9 Lincoln LS that has a rod knock. I have purchased a 2003 3.9 motor for him. I was told when I purchased it that they were compatible except for the intake. Now I am told by others that they aren't. Can anyone tell me if I can use the 2003 engine in the 2000? If so what do I have to change?
  • msgtusmcmsgtusmc Member Posts: 4
    Ask same question @ following link, several have performed same task:
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