Are the threads the same compared to the older plugs? Damaged threads in a cylinder head can be very difficult to repair. I couldn't find any particular brand of spark plug, just that number. So, I am not sure what the OEM manufacturer spark plug is. But if the engine will run, getting the cylinder heads to heat up can help with plug installation because the heat causes the cylinder heads to expand. That may help some.
These are the wiring diagrams for all 4 Oxygen sensors, the 1st diagram is the same as the 2nd. The 2nd is just the OEM manufacturer diagram.
The Bank 1 sensor 1 and Bank 2 sensor 1 are the front Oxygen sensors that are before the Catalytic Converters, just down from the exhaust manifolds. Both Sensors number 2 are after the Converters.
With your multimeter on dc volts, if you back probe the oxygen sensor connectors (starting with the front sensors) with some T pins or small enough pins to slide down the wire into the back of the connectors so you can get a reading of the sensors voltages with them plugged in and engine running.
The Bank 1 sensor 1, purple wire is the Signal wire, and the other meter lead on a Ground location, the front sensors should have a voltage reading fluctuating from around 0.2 volts to 0.8 volts. So around a 0 to 1volt swing. If either of the front sensors are not fluctuating with these voltage readings with the engine warm, that's an issue. The Bank 1, 2 sensor 2's reading should be a steady voltage, usually around 0.5 to 0.7 volts. If either of the rear sensors have a voltage level that is stuck low, around 0.1 volts or even 0 volts. These types of readings will cause the ECM to see a lean exhaust when it might not be a lean exhaust. If the rear oxygen sensors are fluctuating the same as the front sensors, that is a sign that the Catalytic Converters have failed. From what you are describing, it does sound like a restricted exhaust. The converters fail for a number of reasons, but when they do, you will get spark plugs covered in soot. The engine will not be able to take in air because the exhaust cannot escape. You might also hear a hissing noise. Unbolting and dropping the front the Converters can reveal the issue if you don't have a way to do a back pressure test. Even dropping the front of one of the converters you will notice a huge difference in power right away. It will be loud, but when the exhaust can escape, the engine can breathe again.
Sorry for the long post.
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Saturday, March 25th, 2023 AT 8:18 PM