Replace o2 front and still backfire with code po171

Question

I had no check engine light on but had codes ran anywas and got po171 so I changed the front o2 sensor and it's still backfiring a few months back had a tune up I was wondering what it could be thanks

Answer 1

P0171 Fuel trim lean bank 1

What you have is a lean misfire,The 02 sensor are just reporting the condition, what you need check fuel pressure , the specification at idle should be at 49 psi. Recheck the sparkplug wire condition and the cap and rotor ,replace if necessary