Question about Chevrolet Cavalier

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I have an 04 cavalier. Code P0172 mechanic changed upstream 02 senor. light came back on. Brought back to mechanic he changed the downstream, light came back on. I changed fuel filter, spark plugs, oil change from gm (light went out on the day it went in) yesterday changed the fpr light stayed off most of the day then back on today. Ran a test Fuel system 1 CL Fuel system 2 cl - fault Calc load 43.53 ECT (F) 186 STFT B1 -5.47 LTFT B1 -17.97 MAP in HG 13.29 Eng Rpm 2357 Veh speed 43 Spark Adv 32.00 IAT (F) 51 TPS % 16.86 Emission status red C EV Flashing on OBD 2 innova reader Also used a different one earlier and it said the catalyst was not ready and the evap system not ready ( Key turned car not on) I have had it at the mechanic. I am just very confused.

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  • Jeremy W.
    Jeremy W. Mar 19, 2011

    What engine?

    Whats the fuel pressure at?

  • asantoro07 Mar 20, 2011

    Engine is a 2.2L Ecotec 69,500 Km

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1 Answer

Think your guy changed O2 Sensors ,
but didn't consider that your sensors PO172
is rich,because it is correcting for a lean condition


I'am going to really guess here

The EVAP has leaks,but no codes set,
partially driving the system lean (Vacuum Leaks)

The Converter is sort of out there as
not working well either

I would smoke the EVAP System and everything else,
intake manifold etc

I think you will find this by MAYBE even just looking
for a bad hose leak

Is that data from your mechanics scanner ?
What is their theory ?

Bank 1 has a vacuum leak I think !! ??

Posted on Mar 19, 2011

  • Jeremy W.
    Jeremy W. Mar 20, 2011

    Than why are fuel trims lean?

  • asantoro07 Mar 20, 2011

    I have had it at the same mechanic now about 4x, today i took it to someone else. He suspects the catalytic converter. I can here the EVAP system and to me it sounds like there is a leak around it in that area. Also when the FPR vacum hose was taken of suction was very limited. It tonight didnt start great and it seems to lag in the start of acceleration I notice it in 5th gear more so.
    The codes were taken off an OBD 2 reader, I am not sure if my other post is on here regarding the exhaust today after mechanic test drove did smell like eggs a bit that is why he thinks could be a partial clog. I cleared the mil light tonight again and took the readings

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