P0303 GMC 2002 Envoy - starts good and runs great cold, 2 minutes later misfire occurs HELP

Question

after 600 miles on a 800 mile return home. 2002 envoy was misfiring terribly. made it home.

next day, started up with no symptoms of misfire. 3 miles down the road engine started misfire Bad.

Went to Auto Zone and got a P0303 code.

Everything runs super GREAT when cold.

Sensor? Plug?

Help

Answer 1

P0300 Random misfire

P0303 Misfire number 3 cylinder

What you need to check is a common problem,with the fuel pressure regulator , if this fuel regulator rupture it will put extra fuel into the intake manifold, and will cause misfire number 3 cylinder and also random misfire, The location of fuel regulator is at number 3 cylinder, when it idle rough, pull the vacuum hose of the fuel regulator if fuel comes out of the regulator a replacement will be required and so will a oil change,