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theGreatDane

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So i have a 1999 Ranger Supercab, 4x4 with a 4.0 and a 5 speed. A few months ago it started stuttering when cold, when i would accelerate, but would go away after 5 or so minutes of driving, and often less than that when i would floor it.

Yesterday, however, it started stuttering more often, and after starting it up last night, the stutter did not go away, and was accompanied by a rattle (like a can full of marbles being shaken) at above 3k rpm. It now stutters in all rpms, has the rattle, idles really rough, the exaust smells gassy, and the check engine light has come on. When i pulled the codes, i found a P0306 code (cylinder 6 misfire).

I just replaced the plugs and wires about 2000 miles (2 months ago). When i pulled the #6 cylinder plug, it looked normal, and the gap was good (.052). I do not even know where to start, and do not want to just start replacing things wildly hoping they help.

What should i do?!?!?!?! :dunno:
 


RangerSVT

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What plugs did you get? If you got Bosch plugs or anything besides double platinums, that's your problem. I bought regular platinums for my truck once trying to save money. I got about 3k miles then started misfiring. Swapped to dp's, ran great for another 35k miles til I pulled the motor for a V8 swap...

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theGreatDane

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i dont remember what kind they were, i know they were the middle grade ones that they offered me at auto zone. not the standard ones, but the next step up.
 

RangerSVT

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They will probably regular platinums you need to get double platinum. Look on the floods if you see one 'p', then its regular platinums, if there is 'pp', then its double platinums. If its any type of Bosch plug, replace it. Ford and Bosch plugs don't play well together

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theGreatDane

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alright i just picked some double platinums up, and will see if that works. awesome truck by the way too.
 

theGreatDane

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i pulled the plugs, and they were autolight double platinums. however, the #6 was dirty? i replaced the #6 plug, and it now runs great. any ideas as to why the plug was dirty?
 

pillen140

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I thought you pulled the plug and it looked fine?
 

RangerSVT

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Thanks, but what truck you talking about? LOL...
On the dirty plug, what do you mean by dirty? You might want to have your injector cleaned or replaced. A new fuel filter would help too. There is nothing else in the cylinder but air and fuel. Dirty air is ruled out since its only one cylinder, so its either bad fuel/contaminated fuel, or you have oil getting into the cylinder. A bad valve seal or broken piston oil ring could also be the cause if its oil thats on the plug...


SVT
 

theGreatDane

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SVT it's awesome. but the threads on my plug were dirty (combo of oil and dirt it's what it looked like)
 

RangerSVT

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If it was on the threads and not the tip, then it probably was getting a bad ground causing the rough idle/misfiring of that cylinder. As long as the oil was not on the tip I'd say you have nothing to worry about...

SVT
 

fords4me

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Hello. Not sure if you found your problem, but on the later 4.0 pushrod motors they have an issue with the heads cracking between the intake
and exhaust valve and as the engine cools the crack will expand and seep coolant into the combustion chamber. When you go to start it cold, it will miss for roughly a minute give or take until it can burn off the coolant and eventually foul the plug. I had a 2000 Ranger do it, a buddy had a 2000 Explorer do it, and my wifes friend had a 99 Explorer also do it. You can keep changing the plug and it will be fine for a while, I limped mine for about a year until I could afford to replace the head.
 

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