I`ve been working on a 93 pontiac lemans that has me baffled. It is sputtering through the exhaust, and sounds like it is missing on one cylinder.
So far I have replaced the cap,rotor,plugs,wires,fuel filter,fuel pump and pickup screen.(basic normal tune up parts)
I`m getting a lean O2 reading on the diagnostic,(hence the new fuel pump) but no other codes have shown up.
I`m also getting a backfire through the intake under acceleration. it does sound very much like it is running out of fuel, but it has better than 1/2 a tank.
I have checked compression, and all cylinders are within specs (159-175psi) I have even put air pressure to each cylinder,and turned the engine over by hand until the valves closed to be sure that I had no burnt valves.
Any thoughts?