02 impala codes 403, 405, 440

[SmilinJack]

I am working on a friends car with these codes. 3.4 liter. Where do I start?! Could a plugged cat cause any of these codes? I know there was a recall on cats for these cars. Had a 303 code, changed plugs and wires and code cleared. Any help is appreciated. She has limited income so going off replacing things at will is a no go. Car idles rough but still gets it upon hard acceleration. Has 170,000 miles.
Thanks for any advise.

[IffyG]

Off the top of my head, P0440 is most likely a problem with the gas cap (commonly not tightened or its just worn out). Can't help you with the others though.

[98ss]

Sounds like the egr is stuck slightly open. Have you tried cleaning that out?

[buzzstpoint]

P0303 Cylinder 3 Misfire Detected
P0403 Exhaust Gas Recirculation Circuit Malfunction
P0405 Exhaust Gas Recirculation Sensor A Circuit Low
P0440 Evaporative Emission Control System Malfunction


At this point, since you replaced the plugs and wires. I would clear the codes and see what comes back.

[SmilinJack]

Thank you for the quick replies. Upon further investigation, the egr is frozen partially open, and the electrical plug on the valve itself is in rough shape. Since a new egr is outrageous in price, I am trying the local salvage yards. Also there seems to be oil in the anti-freeze. Maybe intake gasket?
I disconnected the positive cable for ten minutes then rechecked codes. Still the same four. Cylinder 3 still has misfire. I tested the coil and it was ok. The 303 code came back after about ten miles on new plugs and wires.

[98ss]

Do you have access to a compression tester? If so, pull the front three plugs and do the compression test. If you have any questions about ihow to do a compression test, I would be happy to answer them.