Hi Everyone,

My car is a 2011 Ford Fiesta SE Hatch, with 96k miles on it. I recently started getting engine lights, first had to replace Bank 2 Cat sensor, the the Bank 1, now I have an engine light that turns on and off pointing at the Cat Bank 1. I replaced both sensors, then I replaced the spark plugs and the wires with OEM ones.

Now I get a knocking sound like if the car was a diesel truck at idle, but again is random.

The car seems to drive like normal, haven't noticed any lag or sluggish at all, accelerates just fine. The one thing that is odd, is that it seems like I am getting better gas milage since the sensors started happening.

I'm planning on taking it to a mechanic so they can do a checkup and do maintenance on the car. Anything I should have them checked? replaced?

I also noticed a loud fan after I turn on the AC, I'm guessing that needs to be replaced or cleaned?

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Thank you!