Cylinder 6 misfire and EGR code

Hey yall,
New member, but I've already read through the forums to solve a few issues.
I just bought my first ranger and think I may have ended up with a lemon. When I test drove it I thought it just had a vacuum leak. Not much power and a rough idle. I found the leak and got it fixed but still have the same symptoms. So I thought it may have be one of the cat converters stopped up. Had the muffler shop run the codes before they reeplaced one and it is showing a misfire and cylinder 6, and a code for the EGR. I replaced the plugs and wires ( went with motorcraft after using this forum again) but still the same thing. Ran seafoam hrough the fuel tank and vacuum lines thinking maybe the misfire was a bad injector, and the EGR maybe just the line. No success there eithe.r I just pulled the plug outta 6, and also 5 to compare it to, but I don't really know what I'm looking at. My father in law says the EGR is fine and the misfire is the cause of the bad idle. So I figured Id upload these pictures of the plugs and maybe yall could help me on where I need to go next.
I have a huge interest in trucks and am starting school to be a mechanic in the fall, but for now I'm ignorant as all hell.
Thanks,
Jake

The number 6 plug is on the left in the pictures.
http://m1275.photobucket.com/albums/jakemcguire77/

Post the actual code #. the egr is most likely the DPFE.

MISFIRE COULD BE COMPRESSION, injector, coil.

Pictures aren't that good of the spark plug ends.
Google: spark plug condition pictures

Then you can do the comparison.

Missing on a specific cylinder could be the spark plug, the spark plug wire, or the coil.
A timing light can be handy to see if spark at #6 is regular, so see if coil is firing intermittently, also swap plug wires with #5(both ends )
Google: How to Check an Ignition Coil Pack the easy way

It could also be the injector for that cylinder, usually there is enough fuel/air in the intake for a good idle even if one injector is not working or is partially plugged, so if missing is only under load it could be the injector.
A stuck open injector would give you a "rich" code most likely.
And a vacuum leak near the #6 cylinder could cause only it to miss.

And it could be the compression on that cylinder, compression test would be helpful to ID that problem, test all 3 cylinders on that bank, all should be within 10% of each other.
So if you got 150psi, 160psi and 155psi, that would be fine, if #6 was 120psi that would show a problem.

Could even be oil fouling of that spark plug, this shows on the spark plug tip, it could come from a bad oil ring on the piston but more likely it is a leaking valve guide seal.
Under the valve cover and inside the intake valve's spring is a rubber seal around the valve stem, this prevents oil vapor from being sucked into the intake.
The intake almost always has a negative pressure(vacuum), the intake valve's stem passes thru this to the head, so if the rubber seal has a leak oil vapor is pulled in and sits on the top of that valve and is pulled into that cylinder during the intake stroke.
Leaking intake valve guide seals can be ID by coasting down a hill, in gear, with throttle plate closed and engine RPMs high the vacuum in the intake gets quite high, pulling oil vapor in thru any leaking seals, when you step on the throttle watch the exhaust, a puff of blue smoke means oil was pulled in, no smoke means seals are good.


The EGR system is only used under load, it is used to cool the cylinders to prevent pinging(pre-ignition), it also helps lower emissions.
An open EGR valve, not closed all the way, would cause rough idle.
EGR valve can be removed, cleaned and checked, just put a vacuum line on it and use your mouth to suck it open and watch it close when vacuum is released.
Yes the EGRs DPFE module is a common fail point.

Oops, forgot to mention in that post I also replaced the coil pack. And that's how the father in law checked it last night. So next move should be checking compression, can I rent one of those gauges from a parts store? And what's the actual name for those things?
Thanks for the replies by the way.

Yes, you can rent a compression tester, that is what it is called.
You can buy them as well, $20-$40.

Gauge should have a "quick connect" fitting, should also have a flexible hose, 8" minimum length, with a dual thread to fit the two most popular spark plug hole sizes, 14mm and 18mm

The reason for the quick connect is that it makes it much easier to screw in the hose and then unscrew the hose without the gauge attached, before and after the test.
The hose needs to be tight in the spark plug hole but just finger tight, you don't need to use a wrench.
Remove all spark plugs and then test each cylinder by turning engine over at least 4 compression strokes, you will hear the engine slow each time the test cylinder hits the compression stroke, then zero out gauge and repeat on that cylinder before moving to next cylinder.
WRITE IT DOWN, you will not remember, lol.
The gauge will have a schrader valve(or button) to release pressure and zero out the gauge.

Many like to disable the fuel injectors during testing, this prevents raw fuel from "washing" the cylinders, up to you, there should be an EFI fuse in the engine compartment power box, pull it out.
But remember if you do this or your next post will be about a "no start after compression test???", lol.
My personal view is that this is not necessary since all spark plugs are removed.