Hi everyone I am new to this forum and I hope you guys can help me out. I have a 2000 Ford Contour (v6) that just recently started acting up. In park it will idle very rough (and lower rpm than normal) and if you tap the gas pedal the rpm's will shoot up to 2000 and hold for about 6 seconds then slowly drop back down to a very rough idle. The SES came on so I used a code reader to check the codes, I got 5 of them.
p1131 and p1151(both oxygen sensor codes) OBD Trouble Code: P1151 Lack of HO2S-21 Switch, Sensor Indicates Lean
p0171 OBD-II Trouble Code: P0171 System Too Lean (Bank 1)
p0174 OBD-II Trouble Code: P0174 System Too Lean (Bank 2)
p0420 (Cat Convt.) P0420 Error Code: Catalyst System Efficiency Below Threshold (Bank 1)
It seems that the oxygen sensors are detecting a lean condition( could also be trying to over-correct for a rich condition). I checked for vacuum leaks and there are none, I also replaced the Mass airflow sensor, no luck. All of the fuses are good. Last I checked the fuel pressure, it was in spec pressure wise (36-40 lb at idle) but the needle was twitching rapidly, is that maybe a sign that the fuel pressure regulator could be the culprit? With 5 different codes there are a lot of things it could be, so I dont want to throw a bunch of unnecessary parts at it. I'm hoping you guys can give me a little guidance on what I should do next. Do you think it could be the Idle control valve? Perhaps the oxygen sensors or EGR valve? Maybe something completely different. Thanks in advance, Dustin.