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4.0L OHV & SOHC V6 Tech General discussion of 4.0L OHV and SOHC V6 Ford Ranger engines.

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Old 01-20-2016
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Location: Littlestown, PA
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Icon4 Need Help Out of ideas!

I own a 2004 ranger Edge 4.0 4x4 with 223,000 miles on it which ran great, Until I replaced the plugs and wires.
I replaced the plugs w/ Autolite 5144 DP and gapped them to 0.54 as recommended. Now the truck will not stay running. I have checked the wires, reset the PCM, and rechecked the gap with no progress.

The plugs that I removed were badly worn having gaps of 0.75 and higher.
4 of the plugs were 5144's and 2 were Motorcraft OEM, they may have been originals.
At this point I am out of ideas as I have never ran across this in 40 plus years of work.
Any suggestions would be greatly appreciated.

Thanks, Chuck
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Old 01-20-2016
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Check firing order on the coil pack, I get it wrong almost every time I do a 4.0l or 3.0l

3 4
2 6
1 5

that 5 6 4 gets me every time, or the wires get mixed at 2 cylinders, reversed, so trace each one.
If you have checked it 5 times already check it a 6th time.

Ford uses a Waste Spark system, so coil pack only has 3 coils inside and the spark plugs fire in Pairs, one spark is "wasted" on the exhaust stroke, hence the name Waste spark system.
To wire 2 spark plugs to one coil requires Series wiring.
So one spark plug fires from center to tip, the other one fires from tip to center, reverse spark.
Pairs are on the coil, 3-4, 2-6, 1-5

Because of this Ford often installed Platinum tip on one bank and Platinum center on the other bank, cheaper than double platinum.
So you will often find two different spark plugs used, but bank to bank not next to each other.

Other reason to mention this is that you shouldn't use single platinum plugs, double platinum will last longer, or just use regular copper, single is a waste of money because one bank will wear out just as fast as regular copper.
You got DP which is good

Other thing to check is the PCV hoses, they wear out under the elbows so they "look good", when running new wires they could have been moved and are now leaking worse.
These vacuum hoses from early 2000's often lasted about 10 years and then started to get brittle and crack.

Last edited by RonD; 01-20-2016 at 12:08 PM.
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Old 01-23-2016
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Location: Overland Park
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RonD you probably know better than anyone else, are these engines actually spec'd for platinum plugs? Not saying double plats would be much different at all, but I seem to remember hearing somewhere that the engine was designed for iridium.
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Old 01-23-2016
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Platinum is what Ford installed.

Motorcraft if you can find them, Autolite is next best, anything else is fine, but will wear out faster.

My 4.0l OHV "eats" other brands, they don't break or anything just get worn out faster.
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Old 01-23-2016
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are these the original spark plug wires
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