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    #1

    Running Rich or O2 Sensor?

    Hey guys, new around here. I have a question on my 5.0. I'm coming up with a code 42 when the car is running. The code goes away after the car is run for at least 10 minutes and will only come back after it is shut off and turned on again. When it is restarted on a hot start it will run a little rough sometimes at first but most of the time it runs perfect, but 10 minutes running and the code is gone.

    What do you guys think?

    Thanks.
    1986 T-Bird 5.0
    DD '13 VW Jetta S

    Past Panthers: '94 GM, '99 CV, '11 CV
    Tags: None
    #2
    The coolant temp. sensor could be out of range (signaling the ECM of a lower than actual engine temp.) Also, check the fuel pressure regulator diaphram and vacuum hose for a leak into the intake manifold.

    Comment

      #3
      You also may want to check the air charge temperature sensor. They can get covered in gunk and sometimes a cleaning will help.

      Comment

        #4
        That's interesting. I'm definitely going to check the FPR, but I'll also try pulling the sensors and cleaning them. They wouldn't set off their own codes, or only if they were not working at all?

        Thanks, any possibilities like these will be a great help.
        1986 T-Bird 5.0
        DD '13 VW Jetta S

        Past Panthers: '94 GM, '99 CV, '11 CV

        Comment

          #5
          most of the time when you get codes about the engine running lean or rich, it actually is. The sensors seldom code when they are bad, the motor usually just runs shitty or eats gas with no obvious explanation.

          If you're pulling the oxygen sensors, replace them. Cleaning won't help, and by the time you get them out you will not wish to do it again.
          86 Lincoln Town Car (Galactica).
          5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

          91 Lincoln Mark VII LSC grandpa spec white and cranberry

          1984 Lincoln Continental TurboDiesel - rolls coal

          Originally posted by phayzer5
          I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

          Comment

            #6
            Originally posted by gadget73 View Post
            most of the time when you get codes about the engine running lean or rich, it actually is. The sensors seldom code when they are bad, the motor usually just runs shitty or eats gas with no obvious explanation.

            If you're pulling the oxygen sensors, replace them. Cleaning won't help, and by the time you get them out you will not wish to do it again.
            I was referring to cleaning the ACT/ECT sensors, if I go through the trouble to take the O2's out, new ones are going in. Lol

            Code 42 is only the passenger side O2 so I'm thinking that replacing that O2 may be my first step since they're fairly cheap. My confusion is, if it really wasnt working correctly, why would the code go away after driving for a little while?
            1986 T-Bird 5.0
            DD '13 VW Jetta S

            Past Panthers: '94 GM, '99 CV, '11 CV

            Comment

              #7
              Because it's not running lean/rich. It's throwing the code cause that's what it's doing. The ECM is getrting the signal from the sensor saying 'I'm running rich/lean'. In other words, the sensor is operating correctly.

              Also if it's lean/rich on one side, look at the injectors on that side. There might be a problem with one of them.


              '93 T-bird
              '03 Silverado ECSB

              Missed:
              '88 Mark VII
              '86 CV

              Comment

                #8
                key on engine off code? the car should be warm when you check the codes. no codes when warm is good.
                Give a man a fish and he will be fed for a day. Teach a man to fish and he will promptly forget that he once did not know, and proceed to call anyone who asks, a n00b and flame them on the boards for being stupid.

                Comment

                  #9
                  Originally posted by cld783 View Post
                  key on engine off code? the car should be warm when you check the codes. no codes when warm is good.
                  The 42 I get is KOER and it's when warm. The strange thing is that the service light is on only for the first 10 minutes of driving. Even if I drive for an hour, shut it off and start it up immediately, the light will be back for the first 10 minutes of the drive cycle.

                  I guess I'll start with testing fuel pressure and then work through the sensors.
                  1986 T-Bird 5.0
                  DD '13 VW Jetta S

                  Past Panthers: '94 GM, '99 CV, '11 CV

                  Comment

                    #10
                    the CEL behavior does make me think its temperature sensor related. 42 is an oxy sensor code though. What do you get for stored codes? Few thing actually set that light off.
                    86 Lincoln Town Car (Galactica).
                    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

                    91 Lincoln Mark VII LSC grandpa spec white and cranberry

                    1984 Lincoln Continental TurboDiesel - rolls coal

                    Originally posted by phayzer5
                    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

                    Comment

                      #11
                      No stored codes. No codes KOEO, only the KOER 42. BTW, this on a T-Bird, not a Vic but it's the same non-HO 5.0 as the Panthers.
                      1986 T-Bird 5.0
                      DD '13 VW Jetta S

                      Past Panthers: '94 GM, '99 CV, '11 CV

                      Comment

                        #12
                        hm, thats odd. if the CEL comes on, it should be storing a code.

                        and yeah, 5.0 EEC IV is effectively all the same as far as codes go. Same controls and sensors and whatnot. It only got different in later years with the 3 digit codes.
                        86 Lincoln Town Car (Galactica).
                        5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

                        91 Lincoln Mark VII LSC grandpa spec white and cranberry

                        1984 Lincoln Continental TurboDiesel - rolls coal

                        Originally posted by phayzer5
                        I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

                        Comment

                          #13
                          I would test the coolant temp and air charge temp sensors to make sure they're actually working. I know when the ECT on my 88 was caked in crap and not sensing for crap the car ran like crap. It would start running right later on, but initially it was crappy.

                          Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
                          rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
                          Originally posted by gadget73
                          ... and it should all work like magic and unicorns and stuff.
                          Originally posted by dmccaig
                          Overhead, some poor bastards are flying in airplanes.

                          Comment

                            #14
                            Really no stored codes? Does that mean you got an 11? Because if it didn't give you anything, you did it wrong.

                            Ground the self test wire. Turn key on. If there are really no codes it should give you blink--blink-----blink--blink----------blink-----------blink--blink-----blink--blink.
                            That's an 11-11 for the current self test (it repeats the codes), then the separator pulse to change from current codes to memory codes, and then another 11-11.
                            Originally posted by gadget73
                            There is nothing more permanent than a temporary fix.
                            91 Mercury CP, Lopo 302, AOD, 3.08LSD. 3g upgrade, Moog wagon coils up front, cc819s in the back. KYB GR-2 police shocks. Energy suspension control arm bushings. Smog deleted.
                            93 F-150 XLT, 302, ZF 5-spd from 1-ton, 4wd.
                            Daily--07 Civic Coupe. Bone stock with 25k miles
                            Wife--14 Subaru Outback. 6-speed.
                            95 Subaru Legacy Wagon--red--STOLEN 1/6/13

                            Comment

                              #15
                              Originally posted by 91waggin View Post
                              Really no stored codes? Does that mean you got an 11? Because if it didn't give you anything, you did it wrong.
                              I'm using an Innova Ford Code scanner and when I do the KOEO test it gives me an 11. I will definitely look at the ECT and ACT sensors when I get a chance this weekend. I have to also pick up a fuel pressure gauge so I can check on that too.

                              Its really weird because the car runs great 99% of the time, doesn't smell rich(other than cold start) and the service light is gone after 10 minutes of driving every time.
                              1986 T-Bird 5.0
                              DD '13 VW Jetta S

                              Past Panthers: '94 GM, '99 CV, '11 CV

                              Comment

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