3 sparkplugs look fine...4th is dark and smells like gas...picture...

[85GTKid]

What would cause 3 plugs to look the same and the 4th to be dark and moist smelling like gas?

 

[88stangmangt]

fouled up......................like it is geting bad spark.............what do you have them gapped at???? check out your wires......................do you have a inline spark tester? (it's a cheap tool you put between the dizzy cap and the wires and it will blink if you have spark)........

 

[87'GTstang]

fouled up......................like it is geting bad spark.............what do you have them gapped at???? check out your wires......................do you have a inline spark tester? (it's a cheap tool you put between the dizzy cap and the wires and it will blink if you have spark)........

I agree. Any fuel that is "left over" unburned un a combustion chamber that basically burns all fuel until there is no more to burn, and you can walk away with fuel still in there, then it isn't burning.

Definitely check for spark as 88stangmangt said. Another cool tool you can use is from sears and all you do is lay it against a spark plug wire and it will light up if it sense a magnetic field. Again, also check for spark gap. It sounds as if anything you have too little of a gap. Good luck

 

[MustangMuscle86]

Possibly detonation in that cylinder from running rich.

 

[dastang2]

it is fuel injected, because if it is, i bet your fuel injector is stuck open like it did on my 3.8 once.

 

[85GTKid]

it is fuel injected, because if it is, i bet your fuel injector is stuck open like it did on my 3.8 once.

carb...

 

[dastang2]

do a compression check, you could have a bad valve or seal as well.

 

[2slo93]

i have this exact same problem...i replaced my valve stem seals and that helped a little. Odds are that you have either a bad valve stem seal or guide. what cylinder heads do u have?

 

[85GTKid]

i have this exact same problem...i replaced my valve stem seals and that helped a little. Odds are that you have either a bad valve stem seal or guide. what cylinder heads do u have?

E7's with lower miles...hmm. Well we swapped the plug and will see if it wasnt a bad wire conecction or bad plug first.

 

[87'GTstang]

i have this exact same problem...i replaced my valve stem seals and that helped a little. Odds are that you have either a bad valve stem seal or guide. what cylinder heads do u have?

All valve stem seals do is "wipe" the oil off of the valve so it doesn't get in the combustion chamber. If it is worn valve guides then that wouldn't really cause a fouled plug or explain unburned gasoline. If you have a lot of slop and play then the entie cylinder head is due for an overhaul. It has to be not enough air or not enough spark. There is no reason as to why 1 out of 8 cylinders is acting like that beacuse it is carb. If it were EFI then you could narrow it down because each cylinder has its own spark AND fuel injector for these cars. Still check those spark plugs or even further make sure the contact for that cylinder inside the distributor isn't worn out so bad that a poor connection is made.

Also how poorly does the engine idle and revv to higher rpms?

 

[2slo93]

the reason it would smell like gas is because the oil has foweled the plug making it not fire completely hence leaving UNBRUNED GAS! However i do beleive their is a problem with carbed 302's having problems getting sufficient air to the 4 and 8 cylinders. do you have an aftermarket intake?

 

[87'GTstang]

the reason it would smell like gas is because the oil has foweled the plug making it not fire completely hence leaving UNBRUNED GAS! However i do beleive their is a problem with carbed 302's having problems getting sufficient air to the 4 and 8 cylinders. do you have an aftermarket intake?

Point taken. That would lead me to my next question then, is there excessive oil consumption on the vehicle or is the coloration of the exhaust blackish?

 

[85GTKid]

the reason it would smell like gas is because the oil has foweled the plug making it not fire completely hence leaving UNBRUNED GAS! However i do beleive their is a problem with carbed 302's having problems getting sufficient air to the 4 and 8 cylinders. do you have an aftermarket intake?

The plug in question is the #4 plug. I have an edelbrock performer intake. The exhaust doesnt really have a color that i have noticed. and no there is little to no oil consumption. Also, engine seems to rev and idle fine. It does have an exhaust leak though that is either near the #4 cylinder or at the header-h pipe flange.

 

[87'GTstang]

The plug in question is the #4 plug. I have an edelbrock performer intake. The exhaust doesnt really have a color that i have noticed. and no there is little to no oil consumption. Also, engine seems to rev and idle fine. It does have an exhaust leak though that is either near the #4 cylinder or at the header-h pipe flange.

Then how is the overall power, but more so, how is your gas mileage?

 

[88stangmangt]

I agree. Any fuel that is "left over" unburned un a combustion chamber that basically burns all fuel until there is no more to burn, and you can walk away with fuel still in there, then it isn't burning.

Definitely check for spark as 88stangmangt said. Another cool tool you can use is from sears and all you do is lay it against a spark plug wire and it will light up if it sense a magnetic field. Again, also check for spark gap. It sounds as if anything you have too little of a gap. Good luck

got that one too.............

 

[BullittStangV8]

ahhh reminds me of the plug out of my 65's 289...Compression tested the same cylinder as the bad plug...0. Nice. Ended up being a bent valve, fused the piston to the cylinder head..Mine was obvious though as there was only 3 fires from the left bank, and 4 from the right. It was amazing that it was still running enough to limp home...Im sure yours is nothing as serious.
Mike

 

[TT91]

Possibly detonation in that cylinder from running rich.

Detonation is caused from running lean, not rich. Having one spark plug covered in fuel isnt bad. What do you think happens the fuel from the injector as it gets shot into the cylinder and the spark plus doesnt fire cuz you just killed power....it sits there. very simple. If all of your plugs were wet, then that would be an issue

 

[85GTKid]

Then how is the overall power, but more so, how is your gas mileage?

Power is good and mileage is crappy but good for my stang.