Reply to "The spark plugs in my new Pantera (5253) are running black. I am seeking advice concerning how to proceed."

@4vandproud The exhaust on the car is not original. At some point a set of Speedforce Racing 180 degree stainless headers were installed in the car along with a completely customized exhaust that doesn’t use the original exits. The O2 sensor was simply removed and never put back in the car so the EFI had absolutely no idea what the O2 levels in the exhaust have been. In reading the configuration of the ECU, it appears they just stuck it in Open Loop mode and left it.

This last weekend, I had the appropriate bung welded back into the exhaust and wired up the appropriate sensor for the car, and re-enabled Closes Loop mode in the ECU. However, I have no idea how long the car has been run between the time the sensor was removed and when I put it back into the car. What I do know is that prior to installing the sensor and enabling closed loop mode, the exhaust had probably enough unburnt fuel in it to ignite the exhaust at the tailpipes.

With the brand new NGK 24300 O2 sensor back in the car and closed loop enabled , I’m seeing it run much better at idle and it doesn’t smell as badly of gas as it did before. But I’m pretty sure the damage is done to the plugs as I still get a fuel smell in the exhaust and the car wants to misfire and lurch under light load. I have no idea why someone would remove the O2 sensor  from an EFI system.

I have owned the car for three weeks now, so everything currently wrong with the car is basically how I bought it. I even had to level out a large dent in the floor pan on the drivers side that caused the seat to tilt towards the center of the car at a pretty steep angle because someone thought that the floor pan was a great lift point for a floor jack.

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