A while back (about 2k miles ago) I had a pair of codes on the Mountaineer (5.0L V8). One was for an EGR valve (which was replaced at the shop) and the other was 0308 which I was told was a problem with spark on the #8 cyclinder. The shop replaced the #8 spark plug which they told me was fouled. The codes were cleared and did not return for the interval. A few days ago it popped the CEL on again and the code is again 0308.

I have read that this might be due to bad plug wires or even a bad coil pack. Would that cause the plug to be fouled again? When it was looked at again (being only 2k old) it was fouled. Otherwise, what else can cause this? The exhaust from the tail pipe does not have any coolant smell and there is no sign of any smoking on it (oil or coolant based) that I can detect.

A little history on that #8 cylinder in case it is appropriate. Apparently when the previous owner had the plugs done that particular one was a problem as they broke it off in the block and had to take the engine appart to get it out (this is what I was told). That was a long time ago but I am not sure if it would relate so I added the info.

I have also read, on this board, that in some cases a 0308 code can indicate that I have a leak in the head gasket. I would expect that I would be loosing coolant (I can not see the level in the tank change) or maybe burning oil (which I do not think I am, but at 178k on the engine it does use some)?

What would y'all recommend my next course of action should be. I need to get this CEL out as the truck is due for inspection in about 2 months and they no longer pass them if there are emissions related problems on the vehicle (heck any CEL in New York State now causes you to fail... as does just clearing the computer and having pending codes).

Other things that I have noticed is a ticking sound during slow acceleration from a stand still. It is worse when it is cold and pretty much goes away once the engine is hot (though you can still hear it if you listen carefully). This sound is on the passenger side of the vehicle. Someone that is more knowledgeable than me thinks that it is an exhaust leak that I am hearing. I thought it sounded like an injector (as my old Chevy 3.1L made similar sounds when it got up there in miles), but even a good course of cleaners does not change the sound (which it did in my Chevy).

Right now I think I will have the plugs replaced (all of them, as I do not know how long it has been since that was done) as well as the plug wires.

thanks for any input/advice.
-John

 

John, with that many miles on it, I'd suspect oil fouling on the number 8 plug. It could be from a broken or worn piston oil control ring, or from worn valve seals on the number 8 cylinder.

For a quick and dirty fix, you can go up a couple heat ranges on the number 8 plug; that may reduce the fouling. The next step would be to pull the valve cover off and look at the valve seals.....