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  • AFR at idle

    hey guys., whats going on? what is the typical average afr at idle? im around 14.7 but smell a little rich. what do you guys read? thanx..

    alex
    Must Go Faster, Faster Untill The Thrill Of Speed Overcomes The Fear Of Death.

  • #2
    Its set by the throttle position switch signal to the ecu (I thought)
    Try not to be a Yahoo

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    • #3
      crowbar wrote: Its set by the throttle position switch signal to the ecu (I thought)
      The afr is set by the tps? Gonna go with no on that one bob. TPS is just one of many factors that go into the equation.

      Sup: Are you logging it at idle to get that? Does it stay consistent?
      http://z31performance.com/forum/viewtopic.php?f=5&t=147

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      • #4
        The throttle position switch IS the idle signal. The afr and also the timing are a function of it. That's why you disconnect it when setting the timing.

        Sup, have you set the timing with the TPS disconnected?
        Try not to be a Yahoo

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        • #5
          crowbar wrote: The throttle position switch IS the idle signal. The afr and also the timing are a function of it. That's why you disconnect it when setting the timing.

          Sup, have you set the timing with the TPS disconnected?
          Really, on what years all of them? We set the timing with everything hooked up...
          89' Turbo-R.I.P. (scrapped)
          87' NA all parts swapped from 89', Stance, 3.3 long block, hx35w, Injector Dynamics 1000cc, isky cams, pathfinder intake, front mount, megasquirt v3.57 w/MS3X
          07 Frontier XE <----(turd) daily

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          • #6
            crowbar wrote: That's why you disconnect it when setting the timing.
            What? Wouldn't disconnecting it open the circuit?
            I thought the circuit should be closed for timming set at idle.
            imagination is a virtue

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            • #7
              crowbar wrote: The throttle position switch IS the idle signal. The afr and also the timing are a function of it. That's why you disconnect it when setting the timing.

              Sup, have you set the timing with the TPS disconnected?
              please take your bad info to nissanforums or zcar or some other site where you wont waste our time. there are about 20 variables that affect AFR at any given engine speed.
              Nearly all men can stand adversity, but if you want to test a mans character make him a moderator.

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              • #8
                Well 'we' are not discussing 'any given engine speed'. We are discussing idle. And the AFR at idle to be specific.

                The idle switch condition is THE signal that tells the car it is at idle, and what AFR and timing to use.

                The technician only looks for O2 signals (mode 1) with the TPS attached. The field shop manual DOES differentiate between the AFR test at idle because it instructs that technician to disconnect the TPS before checking mode 2 afr. This is called out in the Mixture Ratio Feedback System Inspection in the EFEC chapter.

                In other words, the car when at idle, uses a different afr than when it is not at idle.

                I also believe when adjusting the MAF, the TPS is disconnected also.

                As far as the timing, many aftermarket manuals call out disconnecting the TPS. This may be incorrect. The FSM calls out disconnecting the idle up solenoid only before setting the timing (vg30e). If this actually moves the timing would be the issue.
                Try not to be a Yahoo

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                • #9
                  no, i did not set the timing with the tsp unplugged. and the ~14.5 afr is pretty steady. and no one answered my question yet :?
                  Must Go Faster, Faster Untill The Thrill Of Speed Overcomes The Fear Of Death.

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                  • #10
                    Could you open the TPS and get a reading at 'idle' also? Just out of curiousity.,
                    Try not to be a Yahoo

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                    • #11
                      You can Idle anywhere from 14.7 (stoic) to 18.0

                      I would think that the leaner you could go, the better... as long as it idles how you want it to.
                      86 hardtop shell, 93 SC300 engine, 95 soarer bellhousing, 91 supra transmission, 95 Q45 differential hubs and driver's side axle, 1992 300ZX turbo driver side axle and calipers, 2004 350Z Rotors, 87 300ZX front end/hood, 1999 Viper radiator, 1992 Mustang throttle body. Lots of glue and tape to keep it all together.

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                      • #12
                        Well, I just conducted a little test.
                        Car at operating temp
                        check timing at idle= +22
                        unplug tps, recheck timing =+22
                        replug tps, check timing =+22
                        imagination is a virtue

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                        • #13
                          Did that test generate a tps error code?
                          Try not to be a Yahoo

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                          • #14
                            I dont know. Hell, that reminds me I ought to reset it considering my cas went bad the other day. Its late and my car is too loud to be goofin around with right now. I dont want to bother the neighbors.
                            Go tinker with yours.
                            imagination is a virtue

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                            • #15
                              crowbar wrote: Well 'we' are not discussing 'any given engine speed'. We are discussing idle. And the AFR at idle to be specific.

                              The idle switch condition is THE signal that tells the car it is at idle, and what AFR and timing to use.

                              The technician only looks for O2 signals (mode 1) with the TPS attached. The field shop manual DOES differentiate between the AFR test at idle because it instructs that technician to disconnect the TPS before checking mode 2 afr. This is called out in the Mixture Ratio Feedback System Inspection in the EFEC chapter.

                              In other words, the car when at idle, uses a different afr than when it is not at idle.

                              I also believe when adjusting the MAF, the TPS is disconnected also.

                              As far as the timing, many aftermarket manuals call out disconnecting the TPS. This may be incorrect. The FSM calls out disconnecting the idle up solenoid only before setting the timing (vg30e). If this actually moves the timing would be the issue.
                              are you saying that you will see the same afr with 38psi of fuel pressure that you will with 100psi?

                              same afr if injectors are sticking?

                              same afr with 300 duration cam lobes?

                              i could go on...
                              Nearly all men can stand adversity, but if you want to test a mans character make him a moderator.

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