Odd Misfire
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Joined: Nov 2017
Posts: 46
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Odd Misfire
2005 F-150 XLT 5.4L Triton
When is cool out and engine cold:
When started it will run very smooth for a few minutes. It will suddenly begin to miss. Will throw code for either 4 or 8 and sometimes both. Once running temp gets to same point each time (half a graduation before mid-range om gauge) it will smooth out again.
I have noticed that if I sit in truck and maintain 1000 rpm, until gauge covers first graduation, it will not begin to miss.
I am thinking plugs and MAYBE coils.
It seems to me at a certain point, the plugs foul due to increased richness and possibly (hopefully) cold spark.
Does this sound sensible?
When is cool out and engine cold:
When started it will run very smooth for a few minutes. It will suddenly begin to miss. Will throw code for either 4 or 8 and sometimes both. Once running temp gets to same point each time (half a graduation before mid-range om gauge) it will smooth out again.
I have noticed that if I sit in truck and maintain 1000 rpm, until gauge covers first graduation, it will not begin to miss.
I am thinking plugs and MAYBE coils.
It seems to me at a certain point, the plugs foul due to increased richness and possibly (hopefully) cold spark.
Does this sound sensible?
Thread Starter
Member
Joined: Nov 2017
Posts: 46
Likes: 1
That was on my mind when I wrote... 156K and unsure of plugs. I find it believable that maybe previous owner could have changed out plugs 1-3 and 5-7 and decided to skip back plugs due to breakage and difficulty to get to.
