1991 Chevrolet K1500, 4.3 V6. Plugs only have a few hundred miles on them but are Fowler. Two reasons, it’s t it burns oil due to bad valve guides. Second, vehicle was running rich due to a missing emissions component. I installed an oxygen sensor spacer this evening. Vehicle runs quieter, more power, and shifts smoother. If it was running rich due to the need for the O2 spacer, will the plugs eventually clean themselves up? I plan on running a heavy dose of Seafoam as well.
Will spark plugs clean up by driving.
- Thread starter otis24
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A spacer on the upstream O2 will cause primitive fuel injection to run leaner.
The plugs are Autolite Iridium. I will probably replace the #5 plug because it was fouled the worst.
Just unplug the O2 & run it in open loop, These old 1 wire, single bank feedback system's drop out of closed loop fueling anytime the engine is at idle more than a few seconds.
They might clean up IF you stopped the oil and fuel contamination. Since it's still burning oil they probably won't clean up.
They call them spacers but they are mini cats. this means the oxygen sensor sees less oxygen, and leans the mixture.
Yes they will and they will clean up fast too, if the air/fuel mixture is back to somewhat normal levels. Driving more aggressively and using higher RPM will also help. Unless your valve guide seals leak a lot and you have oil fouling and not fuel fouling.
I’ve been messing with carburetors all my life, and reading spark plugs is one of the checks you do to see if your carb is tuned correctly.
I’ve been messing with carburetors all my life, and reading spark plugs is one of the checks you do to see if your carb is tuned correctly.
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O2 sensors produce a voltage signal because of the differential of the exhaust and and air in the atmosphere.
They also need to be above a certain temperature to work good, otherwise they'll only put out a lean reading.
Yes, but cats remove oxygen from the echaust by combining it with fuel (hence the rich/lean cycles).
These trucks use a non heated O2 sensor, Anytime the sensor stops switching the ECM will drop out of closed loop & ignore feedback from the O2.
In the old days of weak points and coil ignitions, mis-tuned carburetors and leaded gasoline, spark plugs would often foul up in slow speed stop and go driving.
Getting out on the highway for a spirited run was called "An Italian Tune Up"
Getting out on the highway for a spirited run was called "An Italian Tune Up"
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When I was a teen,back in the day,we thought the 'Italian Tune Up'fixed all issues and should be done often,and if the tires chirped,you were doing it correctly. L.O.L.
I added two cans of Seafoam and 16 ounces of Marvel Mystery Oil to a full tank of gas (37 gallons) to help with the cleanup. I also added a can of Bar’s Leaks Engine Seal to the oil to help control the oil leaking past the valve guides. I’ve run this far a couple of days. I pulled the number 5 spark plug and changed it out. It was supposed to be the worst. Honestly it didn’t look too bad. Not sure what it looked like before.
Swap the dead plug into a good hole and good plug back into the dead cylinder. You can use a torch to burn the carbon off the plug. In my experience most fouled plugs, other than Champions, will clean up and run fine.
I was able to get my friend to scan the vehicle with his OBD1 scanner. Vehicle isn’t getting up to temperature. Tried a new radiator cap. No help. Next up is new thermostat. Vehicle is never getting out of open loop due to not reaching temperature and short trips.
