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Q: What would make all three plugs on bank to foul out?

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Truck has a new crate motor with actual miles of only 3500 new plugs wires sensors etc. The truck just started misfiring at cruising speed. It is showing misfire on number two cylinder, I pulled plugs checked all the wires wires are fine. Question is all the plugs on bank to our fouled but all the plugs on bank one look perfect. The truck cranks up fine and holds feel pressure at 55–60. It starts miss firing wants the engine is warmed up and I start cruising down the road. also I checked the EGR valve and did not really see anything wrong with it. I also checked for vacuum leaks and could find none. Thanks for any help or info you might have for me. I also replaced all three CO2 sensors about two weeks after motor was put in .

My car has 156000 miles.
My car has an automatic transmission.

From what you’ve described, you’ll need to have the fuel pressure tested to make sure it holds after tuning the key off. If the pressure drops then you may have a leaking fuel pressure regulator. If pressure is okay then test the O2 sensors to make sure they are working and not shorted out. If you need some help with these checks, consider YourMechanic, as one of our mobile experts can come to your home to diagnose the misfiree and help you make the necessary repairs.

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