hello guys, a little history on the truck. i have changed plugs, wires, coil, fuel filter and the fuel pump. I deal with rough idle most of the time with fairly terrible gas mileage, but i am seeing that's normal. the truck left me stranded twice, so the fuel pump was the last thing we did and it hasn't left me since. before changing the fuel pump, i noticed what seems to have been a misfire around 3500 rpm under acceleration. i first noticed when we were pulling a trailer full of furniture to a family member across state and struggled to get up hills during the trip, always around the 3500 mark. when i changed the fuel pump, i was hoping that this would solve the issue at 3500 rpm, but it hasn't.
I'm 50 years old, so i don't rough house the truck but something is not right. i have also cleaned the MAF. I know its a lot of info, but i am looking for ideas other than plugs, wires, fuel pump, fuel filter and a coil.

Thanks

 

Spark plug gap is listed at 0.044" you may want to try 0.040"

Spark plug gaps are set for general use, so are an average.
For lower RPM and cold starts you want a wider gap, 0.049, "hotter" spark, but less recovery time for coil.
For higher RPM you want a narrower gap, more recovery time for the coil.

Long shot, but make sure spark plugs are gaped correctly, they don't come out of the box gaped correctly

Fuel injectors, you can test the OHMs on these, Ford uses low resistance injectors, so 11-16 OHMs.
A fuel injector is just a needle valve that is pulled open by an electro-magnet, a coil of wire, like a relay or solenoid, technically is IS a solenoid.

If the resistance changes in the injector it could cause an issue in rapid opening and closing situations, i.e. higher RPM
If you test the 6 injectors and 5 are 14ohms and one is 10ohms then that could be the problem.


Another long shot but a possibility is that the 2004-2006 Ranger 3.0ls had a head issue, the wrong size exhaust valve seats, or a bad batch of exhaust valve seats, were installed.
When cylinders got hot, like when pulling a load or going uphill, the bad exhaust valve seat would cause a loss of full compression in that cylinder so a soft misfire was noticed.
Many shops now offer an all electronic engine balance and compression test, and it does work fairly well.
Takes about 10-15minutes to do, you hook up laptop to cars computer and run the tests.

Because the computer can time the crank's spin using the CKP sensor it can detect how much it slows down during compression stroke(spark/fuel is disabled), this can calculate compression in each cylinder
And its pretty accurate, within 10psi of my mechanical compression test, and a whole lot faster, lol.
Balance test uses the same principle but engine is running, each normal firing cylinder adds power to the cranks spin, a soft or hard misfire doesn't add the same amount of spin, computer can see that time difference

 

never heard of over or under gapping the plugs...maybe I will try it

 

Racers use smaller gaps for better higher RPM performance
If you spend alot of time idling or in very cold weather, especially startups, then wider gap is better

I tend to stay within .005 but you can go as much as .010 over or under "average" stock gap

One other thing about Ford's Waste Spark system, 2 spark plugs fire at the same time
This type of system is the oldest spark system ever used so nothing new, your lawn mower uses waste spark, lol.

BUT......because the 2 spark plugs are wired in series one spark plug fires from center to tip(normal) and the other fires from tip to center(reverse).
Doesn't hurt performance but what does happen is that the tip on one spark plug wears out(normal) and the center on the other wears out(reverse).

You will notice that if you compare left and right bank spark plugs.

Point of this is that you DO NOT want to spend money on single platinum spark plugs
Because only the tip OR the center has the extra protection from wear.
Waste of money
So either use regular copper or Double platinum.

Many Fords came from factory with single platinum, BUT, platinum tips on one bank and platinum centers on the other bank, lol.
When you are talking thousands of spark plugs saving a few cents per spark plug matters, but for 6.........well you can decide

 

I put autolite platinum AP104's in it. I pulled them yesterday and tightened the gap up a little and I will see how it runs over a tank of fuel. I appreciate your suggestions RonD, the truck seems to have ran a little better today.