What is a fouled spark plug?NGK wrote:
A: A spark plug is considered fouled when the insulator nose at the firing tip becomes coated with a foreign substance such as fuel, oil or carbon. This coating makes it easier for the voltage to follow along the insulator nose, leach back down into the metal shell and ground out rather than bridging the gap and firing normally.
Many factors can contribute to spark plug fouling. The air-fuel ratio may be too rich as a result of incorrect carburetor adjustment or a poorly performing fuel injection system. Worn piston rings or valve seals may allow too much oil to leak into the combustion chamber, leading to oil fouling. The ignition system may not be performing properly. Prolonged idling or continuous low-speed driving may keep the spark plug from reaching its optimum operating temperature. Using too cold a spark plug can lead to the same problem. Finally, a dirty air cleaner can create a too-rich condition which can lead to fouling.
Fuel, oil and carbon fouling can all be the result of different causes but, once a spark plug is fouled, it will not provide adequate voltage to the firing tip and that cylinder will not fire properly. Therefore, it is recommended that a plug be replaced once it is fouled.
Lots of good pictures on this site
http://www.gnttype.org/techarea/engine/plugs.htmlAs Turtle says...you have intake manifold gasket issue and it will only get worse
VERY common on the 8.1L and that link I posted a few back links to a patented
sheetmetal cover. Back when my Suburban site was still active, several members
listed the same and that GM had a sheetmetal fix on later. Sorry, don't remember
if they were able to get one
Or as been saying...you have a stuck piston ring(s). Either or both compression
ring(s) and oil ring(s)
I've dealt with this most of my wrenching life and that goes back to late 50's
Before SMOG stuff...it was either stuck rings or worn valve guides leaking down
Rarity...head gasket leaking, but am not aware of head gasket issues with the 8.1L.
On my 7.4L and 5.7L GMT400's...yes intake gasket leak issues.
After SMOG stuff...add the PVC and EGR systems as culprits
Another, mainly GMT400, issue is with the OATs Coolant. If O2 has been allowed
in there...it will eat gasketing. Don't know if the 8.1L has coolant running
in the intake/manifold or not. But if this is the culprit, gasket change time...
