Check firing order on the coil pack, I get it wrong almost every time I do a 4.0l or 3.0l
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 11:08 AM.