Changed spark plugs = MISFIRE - Ranger-Forums - The Ultimate Ford Ranger Resource


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  #1  
Old 09-26-2010
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Icon8 Changed spark plugs = MISFIRE

Okay here's the story, I changed my plugs this weekend, those were still the original ones, with 53k on em, I changed the old ones (AGSF-24N-6H) by the ones the dealer sold me (AGSF-24N-8G). Note that I also removed that.... silencer thing in the airbox at the same time.

The truck was running fine before, but now i get occasionnal misfires, sometimes it's worse, sometimes I can barely feel it. At some point it was so horrible, the CEL was blinking.

I think it could be 3 or 4 things....
-these are'nt the right plugs (6H/8G)
-the gap is too great (Note that I assumed it was okay, I just compared with old ones, and to my eye, it looked correct)
-I didnt put ..... you know that grease that I'm suppose to put on the connection wire/plug
-Could it be linked to the silencer that I removed ?? (that one is less probable)

What are your toughts guys ! It gets really annoying.
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Old 09-26-2010
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a blinking cel is not a good thing. im thanking you got the wrong plugs. by any chance did you compair the lenths of the old plugs to the new. the threaded end?
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Old 09-26-2010
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Well I compared real quick when i saw the number was different, but they looked exactly the same.
Note that the cel only blinked for....1 min, when it misfired so much ! I pulled over, let it idle for a moment while i was takin a look under the hood, got back on the road..... and the cel is off since that moment.
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Old 09-26-2010
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Check for unseated boots or cracked plug insulators. Both are common problems after a plug change.
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Old 09-26-2010
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Yeah I guess I'll have to take em out and have a look at them..... while there I should probably check the gap..... anyones knows what it should be ?? I'll also try putting some grease in there. Hope it'll solve the problem.
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Old 09-27-2010
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I replaced my stock plugs with E 3's and found that the #1 plug wire didn't seat to the plug. The plugs are the same length but the seat is higher on the E3 so the plug sits lower in the plug well. Hold them side by side and you'll see what I'm talking about. The boot wont go far enough down the well so I had to trim it down. Not what I wanted to do but it worked.
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Old 09-27-2010
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the intermittent nature of it makes me suspect the connections and wires way more than the plugs.

btw, if you're getting misfires you could check the new plugs and see if one is cruddier looking than the others
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Old 09-27-2010
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I'll have a look at this when I get some time thi weekend. But your problem with the E3s is'nt applying to my case, as I replaced them with motorcraft ones. I'm planning on taking them out, see what they look like, Gap them correctly (still need to know the right gap, and buy that gapping tool), put some stuff for the connection, then road test it ! Hope that solves it.
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Old 09-27-2010
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The gap is .44 for the Motorcraft plug, the E'3's can't be adjusted. I noticed it starts quicker and runs a bit smoother with the a/c on. 2 mpg's better when I kept up with it. I get that way too, I'll do 4 things and then take it for a ride and find its worse then before.....
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Old 09-27-2010
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2mpg is good for a spark plug change...... were your old ones still good ?? or they were... overdue.....
By that I mean.... could you have got the same gain by changing for new motorcrafts ?
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Old 09-27-2010
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Quote:
Originally Posted by Wilbrod View Post
2mpg is good for a spark plug change...... were your old ones still good ?? or they were... overdue.....
By that I mean.... could you have got the same gain by changing for new motorcrafts ?
I did them this year, 22,000 mile (29,000 miles now) because I felt a rough idle with the a/c and the lack of pick up too. They looked clean to me when I took them out but the electrode seemed to be worn down. I never seen what the looked like new but the electrode was real thin.
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Old 09-28-2010
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I changed my plugs at 78,000 miles (ford recommends 100,000) and i was surprised that they were not bad at all.
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Old 09-28-2010
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lol if you did not compare the lingth you could be in a world of ****, you actually can punch a hole through a piston lmao. Sorry not to scare you haha. Just run a basic spark test, should tell you. Just dont touch the wires while its running.....lol.
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Old 09-28-2010
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Quote:
Originally Posted by [email protected] View Post
I never seen what the looked like new but the electrode was real thin.
A thin center electrode means it's a Fine Wire Platinum plug. Rangers have come from the factory with FWPs for the past few years and now they are also the recommended replacement for several years before that.
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  #15  
Old 10-15-2010
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Running fine

Okay just a little update..... I did nothing on the truck.... and it's running fine now, no misfires(that I can feel), and I get about the same mileage as before changing...
.. I'll have a look if the problem gets back.
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