i took my car out the other day,and my check engine light started flashing at me,and the car was not running right...

checked the codes,and this is what i got.

po161
po300
po410
po420

i got to checking around,and noticed the egr on the back of the intake,the bolt was coming out,so i tightened it up. and i had a air leak at the pvc valve.and i have since fixed that also. question is now,where do i start trying to find this.... i know i need to check the usual spark plug wires,and spark plugs.
any help is appreciated.thanks alot.

 

The 161 is the downstream oxygen sensor on the passenger side. It shouldn't affect performance.

The 300 is the dreaded multiple misfire code. Could be any number of things. I'd start by inspecting plugs and wires.

 

P0161 is telling you the after-cat sensor on the passenger side has a faulty heater circuit. Could be the wire, the sensor of the fuse.

P0410 tells you the O2 sensors are not detecting flow into the exhaust manifolds from the AIR pump system, when the PCM cycles the pump and looks for the O2 sensors to go lean. Could be a faulty pump, faulty check valve or melted rubber hose.

P0420 is telling you there is inadequate oxygen storage in the driver's side catalytic converter. Could be the cat, could be the sensor or the harness wires.

Swap the two after-cat O2 sensors. See if the P0161 and P0420 codes stay where they are (wiring problem on the passenger side, wiring problem or dead cat on the driver's side). If the codes follow the sensors, you have one or two faulty sensors.

 

thanks alot guys, i really need to get a set of headers,and delete the egr,i been wanting to get a set of the lpp's, but they cant seem to keep any in stock....i have already deleted the air system,but i just capped off the tubes on the manifolds. and besides checking around the manifolds on the spark plug wires,where else is a likely place??? its pretty hard to see the path of travel under the alternator,and power steering crap... thanks again guys.