2000 Ranger XLT 4x4 4.0L ~ 87K miles

my #3 plug keeps going bad... lots of crud on threads, used my cheap scope camera to look around the valve cover and around the plug, no oil leak.

thought it was the beginning of head gasket issue ? but i have no coolant loss, oil looks fine ( don't notice a loss of oil but i change it by time vs by mileage )

I just get a little miss or idle seems a bit off - change #3 and all is fine. if i wait long enough i will get a #3 misfire code. happens about 6 months to a year..

ideas ?

Thanks,
Tim

 

Welcome to the forum

Head gasket issue would show "steam cleaned" spark plug tip

Could be fuel injector issue, sticking open now and then causing Richer fuel mix, and that blackish residue on spark plug.
I would also check what #1 and #2 spark plugs look like, see if they show lean burn

You might try using an OHM meter on the 3 injectors on that Bank of the engine, to see if #3 is out of spec with the other 2

If you have a Smart phone, a good long term investment is a Bluetooth OBD2 reader, $20-$40, get extension cable with it.
These plug into the OBD2 port on ANY vehicle sold in the US/Canada from 1995 and up.
The Live data from the engine can then be seen on a smartphone, or tablet, with an APP using Bluetooth.
Also reads codes
If you had a leaky #3 injector Bank 1(passenger side) would show negative STFT(short term fuel trims) while driving

Long term investment because this will probably not be the last vehicle you will own.

Also I find on my 4.0l OHV that a can of Seafoam in the gas tank once a year keeps my idle smoother and fuel system working better, 1994 4.0l OHV, 400K, with original fuel pump and injectors, knock on wood, lol

17 year old vehicle with only 87k means it sat alot, about 5,000 miles a year, so could have some clogging in fuel system, and engine seals dry out when an engine sits.
Could be intake valve guide seals dried out and cracked, this causes a bit of oil to leak down the valve stem and it is burned with gasoline causing the blackish residue on the tip.
#3 is at a back of the engine which is where the oil collects in the valve cover when driving, so is most likely place for failing valve guide seal to show up

No real way to check for this, especially since it isn't that bad of a leak if thats what it is.
On your next oil change, assuming you do it yourself
Just after refilling the oil Bank 1 valve cover(where oil filler is) will be full of oil so #3 intake seal will be covered with oil, angle of engine causes this.
Disconnect 4 wire connector on coil pack, so a No Start
Pull off the large air tube on the front of the intake manifold, cover opening with your hand or ??
Crank engine a few times, hand over intake increases vacuum in intake while cranking
Check spark plugs #5 and #6, looking for oil residue on #6

 

Thx for the reply ron, all of the other 5 plugs look fine. i will look into a bluetooth device, i have the cheap meter from harbor freight but it has limited functionality...

Tim

is there a bluetooth device you'd recommend or what to look for in a device ?

 

BAFX units generally get good reviews, $25

Torque Lite is a FREE APP but Torque Pro is worth the $5

Review of both are seen here: www.youtube.com/watch?v=PTxxrURUpFA

The OBD2 ports on all vehicles have the 12volts needed to power the device, so no batteries needed
But access to the OBD2 port can be limited, I find the BAFX fits into most but on some vehicles you have to remove cover panels to plug it in, so an extra step.
Thats where the $8 extension cable comes in, it will fit in pretty much any exposed OBD2 port and then you can plug in the reader to other end of the cable

 

seafoam states high concentration can be used for cleaning, so i used 2 bottles at fill up so we'll see how that goes.

BAFX OBD2 ordered, so i'll read up on how to use torque pro.

Thanks for the tips Ron.

Tim