ysummers

My check engine light started flashing - misfire on the 4th cylinder.
Replaced the plugs an wires, did a head job - still flashes when going above 30mph any ideas? I live in Bethel Alaska so I can't just go have the codes read. Need help I love my truck and don't want to give it up!

tech2

clogged cat convertor? remove the pre cat 02s from the exhaust stream. it will allow the exhaust to bypass the convertor. if the misfire conditon is gone...replace the cat.

ysummers

Are you talking about the catalytic converter and O2 sensors?

tech2

yes
catalytic convertors and bank 1 sensor 1 and bank 2 sensor 1 02

ysummers

Thank you! I'll give those a shot!

LeBron

When remove, are you talking about unscrewing it or unplugging leaving them in?

tech2

unscrewing them.

if the cats are clogged and exhaust gases can't exit the combustion chamber....removing the 02 sensor lets the gases flow out the 02 sensor hole.

LeBron

Well I tried it, it's still misfiring, and engine light flashing over 30mph.. I've also already changed plugs, coils, and MAF sensor.. not sure what else to do..

tech2

what make model year and engine?

LeBron

It's 2006chevy avalanche 5.3 flex