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95 Cobra running lean/wont pass inspection

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  • 95 Cobra running lean/wont pass inspection

    My car is having trouble passing emissions in TX. I could use some guidance from the collective wisdom here....

    Most recent inspecting report from this past week indicates a well running car minus a failure at high speed test for NOx. Prior to this test I have replaced (all since april) plugs, wires, cap/rotor. All oem spec parts from O'reillys, no performance parts. I recently installed new flowmaster 2.5" mini cats as well. maybe 150mi on the cats. Using a friends Matco Monitor 4000 Enhanced scanner, I retrieved the following codes last night after driving home approx 30mi hwy in 107+ temp.

    KOEO
    564- Fan control circuit failure KOEO ( I do hear both fan speeds come on during the test though...)
    181- Fuel system at rich adaptive limit at part throttle, system lean B1
    186- Injector pulse width higher than expected (with BARO sensor) (BARO=barametric psi?)
    189- Fuel system at rich adaptive limit part throttle, system lean B2
    KOER-PASS and Cylinder Balance Test PASS

    After some google fueld semi professional amateur guestadiagnostics, I replace my O2 sensors with NTK sensors as a place to start.

    Drove home tonight, same mileage, approx 90* temp and pulled the following codes.
    KOEO
    564 2x
    SEPARATOR 10
    Keep alive memory codes
    181 2x

    I then ran the fast codes option on the scanner and came up no codes. Re ran the slow code option and got a KAM codes PASS...which I thought was strange...
    KOER codes were
    172- Lack of heated Oxygen Sensor (HO2s-1) switches, indicates lean B1
    136- Lack of heated Oxygen Senosr (HO2s-2) switch during KOER, indicates lean B2
    CBT PASS

    I will clear the codes in the morning and go drive the car since I have not cleared the codes since installing the O2 sensors.

    I know high NOx is caused by high combustion cylinder temps, and I clearly have a lean eng condition, but I'm not sure how to correctly identify the exact cause.

    1995 Cobra #404
    1994 Cobra #1968 **traded**
    1991 LX Hatch 5.0-Sold

  • #2
    And this is the reason my 94 still sits lol. Hope you get this figured out.

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    • #3
      Friend has a 95... same problem until he replaced the cats. He went round and round with that issue for well over a year.
      WH

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      • #4
        What is the cutoff time frame for emissions? 25 years?

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        • #5
          Yep. 25yrs. Car has brand new cats on it
          1995 Cobra #404
          1994 Cobra #1968 **traded**
          1991 LX Hatch 5.0-Sold

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          • #6
            do a smoke test on the Vacuum system

            A car that old I'm sure has started to pull vacuum from somewhere it aint supposed too...My last car was running lean from a vacuum leak at the brake booster

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            • #7
              I will smoke test the car Monday
              1995 Cobra #404
              1994 Cobra #1968 **traded**
              1991 LX Hatch 5.0-Sold

              Comment


              • #8
                With two banks reading lean, you have a global condition. Either vacuum leaks or fuel pressure. Knowing the 5.0L, you're on the right track with vacuum.

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                • #9
                  Originally posted by TX_Snake View Post
                  Yep. 25yrs. Car has brand new cats on it
                  Did you see them put on yourself? Or did you buy it from a guy that told you it has new cats? (that was friend's story lol)

                  Also he didn't start having this problem till he put headers on it
                  WH

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                  • #10
                    Make sure you have your factory timing set correctly with the spout disconnected. If you have the timing off just a little you will fail everytime. I've been down this road a few times. It's why I will only buy cars that are 25 yrs old or have OBDII. It's way easier to pass with OBDII.

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                    • #11
                      Brand new Flowmaster 2.5" cats welded into my O/R H pipe. I was checking timing today but cant read any of the marks, I need a paint pen so I can mark the balancer. I am pretty sure timing is good though. I more than likely have a vac leak, which a smoke test should prove out, or I have a fuel psi issue, which I will also check for tomorrow. Either of those can cause a lean condition.
                      1995 Cobra #404
                      1994 Cobra #1968 **traded**
                      1991 LX Hatch 5.0-Sold

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                      • #12
                        Finally found the root of my problems. The MAF sensor had a low voltage output, indicating it was not functioning correctly. R/R the MAF sensor and reset timing to 10* from the 18* it was set at and now the car runs crisper, pulls harder ,and passed the test.
                        1995 Cobra #404
                        1994 Cobra #1968 **traded**
                        1991 LX Hatch 5.0-Sold

                        Comment


                        • #13
                          Originally posted by TX_Snake View Post
                          Finally found the root of my problems. The MAF sensor had a low voltage output, indicating it was not functioning correctly. R/R the MAF sensor and reset timing to 10* from the 18* it was set at and now the car runs crisper, pulls harder ,and passed the test.
                          Congrats!!! And happy it wasn't too awful.

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                          • #14
                            Good to hear!

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