Spark Plug change interval
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Post Fiend
Joined: Jan 2000
Posts: 5,860
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From: Metro Detroit (Redford)
Spark Plug change interval
I am using the standard Motorcraft plugs and wondered how long folks run them in their 300 I6 engines. I have a '95. The book says 30,000 miles which I say is baloney. My last set ran about 22,000 miles and the electrodes were rounded off hard on one side. The set I am now running is at 10,000 miles and I am thinking to change them now or no later than 15,000 miles (Chilton's says 15,000 for the '87/'88 EFI). Guess I could just get off my lazy rear end and pull one to see, but thought I'd get some imput first. It's not running bad and the plugs, cap, and rotor are fairly new, but the thing takes about 2 seconds to crank over.
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INLINE SIX POWER!
'95 F150 XL300 Cubic Inches of Low RPM Truck Torque! And twin-I-beams too!
"Drive a stick young man! There'll be time for automatics when you're old and unable."
See my gallery, just created 9-02.
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Post Fiend
Joined: Jan 2000
Posts: 5,860
Likes: 4
From: Metro Detroit (Redford)
Spark Plug change interval
>bad and the plugs, cap, and rotor are fairly new, but the
>thing takes about 2 seconds to crank over.
Whoops (brain is skipping more cogs these days
). Not PLUGS, cap and rotor , but WIRES, cap and rotor are fairly new.
>thing takes about 2 seconds to crank over.
Whoops (brain is skipping more cogs these days
). Not PLUGS, cap and rotor , but WIRES, cap and rotor are fairly new.
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Joined: Dec 2001
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Spark Plug change interval
Hi TallPaul,
I've run every set around 50,000 miles. They do round off a little, with the greatest wear on the open side of the electrode (I put a new set in 2 weeks ago). I've been using the 99 cent Bosch plugs from Auto zone. They're hotter than I like and stay pure white on the porcelin.
I've run every set around 50,000 miles. They do round off a little, with the greatest wear on the open side of the electrode (I put a new set in 2 weeks ago). I've been using the 99 cent Bosch plugs from Auto zone. They're hotter than I like and stay pure white on the porcelin.
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Joined: Jul 2001
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Spark Plug change interval
I ran a set of autolite copper plugs for 30k miles. She was hurtin twards the end. When I pulled the plugs they were rounded and horrible looking, along with a cap and rotor that made me wonder how it ever ran in the first place. I put in some plats (can you believe advance auto didn't have any copper plugs for me?) and we'll see how they run. This is on a bone stock '89 F150 (oops, w/K&N panel filter woowoo).
-=Whittey=-
-=Whittey=-
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From: Southern MD
Spark Plug change interval
When I bought my '94 from the original owner with 65,000 miles, it ran great. I decided to change cap, rotor and wires at 69,000 miles before a long trip. It still had the original stuff in it. It dosen't run any better now than before, and gas milage hasn't changed.
Should have just left it alone 'til it gave me a problem...LOL
-------------------------
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'94 E-150 Conversion Van 4.9 / C-6 -- '89 Mustang LX 5.0
Should have just left it alone 'til it gave me a problem...LOL
-------------------------
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Post Fiend
Joined: Jan 2000
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From: Metro Detroit (Redford)
Spark Plug change interval
Well I pulled #4 last night. Looked pretty good. There was a slight rounding of the top of the electrode, some blackening down one side of the electrode, and light brown/grey deposits on one side of the electrode and insulator. The rest of the insulator was white. Guess I am good to 15K or so.
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Joined: Sep 2002
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From: USA
Spark Plug change interval
When I bought my '93 F150 with 4.9L it had 97,000 on the clock. One of the first things I did was change plugs. Just like someone else said, I was surprised it ran at all. They had to have been the original plugs. They must have been burnt to .060 or .070. Funny thing was the new plugs didn't seem to make any difference. Wonder if it has to do with low RPM and low compression?
So you can probably run them way past what you think. But it sure feels good knowing them new parts are in there. So with EFI, I think I'll go maybe 30,000 on these.
So you can probably run them way past what you think. But it sure feels good knowing them new parts are in there. So with EFI, I think I'll go maybe 30,000 on these.
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Post Fiend
Joined: Jan 2000
Posts: 5,860
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From: Metro Detroit (Redford)
Spark Plug change interval
Thanks, as noted above my last change was plugs with 22000 miles on them. I distinctly felt an improvement in performance from the new plugs. But now you have me thinking. Perhaps the new cap, rotor, and wires is helping these plugs last longer. The new wires are Motorcraft and run about 4000 ohms per linear foot (spec says no greater than 5000 per foot); whereas the wires that were in it were under 1000 ohms per foot. I wonder if the old wires (maybe a performance set) were cooking the electrodes with too much juice? If so, maybe these are good for 30,000.
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