Hello i am usually on the diesel forum here but my sisters mountaineer (4.6) is throwing a code of misfire for no 6 cylinder.
recently no 3 spark plug blew out of the head and we have fixed that and replaced that coil and all 8 plugs.
now she has that codee. so i just put a new coil on no.6 and light was right back on.
any ideas on what to do next?
also anyone verify i have the right cylinder? here is what i think they are.
firewall
4 8
3 7
2 6
1 5
radiator.
thanks for any help

 

You have the correct cylinder, and your diagram is accurate. You should start by pulling the spark plug and inspecting it. While you have the plug out, you could check the compression on the cylinder to make sure it isn't abnormally low. You could also swap the spark plug with another one, assuming you don't see something obviously wrong with it. You might also swap the coil with yet another cylinder, then see if the code remains on cylinder #6, follows the spark plug, or follows the coil. If it follows one of the parts, I think that's pretty self explanatory. If it remains on the cylinder then you likely either have a compression issue or a fuel injector issue.

-Rod

 

so a misfire could also mean an injector? I assumed it was just a spark issue

 

If the cylinder is not getting the proper air fuel ratio, it's not going to fire reliably = misfire. Yes, a fuel injector that is allowing too much fuel or one that is not allowing enough fuel can also cause a misfire, as could a vacuum leak that is allowing in too much unmetered air.

-Rod

 

ok so tonight i swapped no6 coil with no 5 coil to see if the problem followed the coil, now got 3 codes no 6 misfire no 1 misfire and randon and multiple cylinder misfires. could this be a bad fuel filter?? or where else may i look?

 

It could be a fuel issue, and if you're going to shotgun a part, a routine maintenance item such as a fuel filter is not a bad place to start. However, I'd rather see you check the fuel pressure at the fuel rail with a fuel pressure gauge to determine if the pressure is within spec.

You mention you now get three codes but mentioned four. Please confirm the code numbers, are they P0301, P0306, and P0300?

-Rod

 

they all said p0301 but a different description

 

any number on what fuel pressure should be at?
key on
running?

 

301 is missfire #1 cylinder. 306 would be for #6. What is your "random" code ? FUel pressure is about 40 psi. Shut motor off and it should maintain that pressure for an hour.. I doubt it is fuel related. 90% of the time, it is coil or possibly the plug.

 

yes im sorry it was 306. gonna put a different plug in it, they were new, im wondering if there are bad wires to the coil at this point. tried 2 dif coils and there so far same issue