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IACV - how do you adjust it?

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  • IACV - how do you adjust it?

    So I got in the garage and tried to get the car to run.

    The car stumbles really bad at idle. If I give it some gas it responds quite well.

    I replaced the IACV during this winters build up. I never adjusted the screw. How should I go about doing this?

    Is it just trial and error? Open it up a bit, turn it over. Not good enough, open up the screw a bit more?

  • #2
    I waited until the engine is all warmed up and adjust it by turning the screw that you can see in between the intake runner. I set mine to about 850.

    Must be nice to have a brand new IACV.

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    • #3
      A search on freshalloy gave me this: "To correctly adjusting the idle, disconnect the Throttle Position Sensor, start up the engine. If it stalls right away, turn the idling adjusting screw counter-clockwise until you can get the motor running at about 750rpm. You also might wanna rev it to about 2,000rpm a few times and let it come back to idle to see if it will stay at 750rpm. If it does, shut off the engine and connect the TPS. Done."

      Going to give that a try tomorrow.

      FRSport sells new SR IACV's. "ONLY" $175.

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      • #4
        I know it's not what you want to hear, but there's a procedure listed in the FSM for it.
        Originally posted by SoSideways
        I don't care what color they are as long as they are LONG AND HARD.
        '04 G35 Sedan 6MT- The DD
        '96 240SX- The Track Toy

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        • #5
          Mine hits whatever I set the target idle to at that water temp in the ECU. I opened it more after adding HKS cams to reduce the duty cycle at idle, but other than that it's pretty tolerant to a wide range of "settings."

          I think your bad idle might be due to a vacuum leak.
          '18 Chevrolet Volt - Electric fun hatch for DD duty!


          DefSport Koni Sleeve and Spring Perch Buy!!!
          http://www.nissanroadracing.com/showthread.php?t=5902

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          • #6
            A vacuum leak is certainly one of the possibilities that came to mind.

            An evening of hunting this down is what I'm facing. Hopefully it'll be a quick fix.

            I cracked opened my FSM on how to adjust the IACV, the steps were written if you had Consult on hand. I was in the EF&EC section. I'll take a closer look in a bit.

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            • #7
              Originally posted by Bumnah View Post
              A search on freshalloy gave me this: "To correctly adjusting the idle, disconnect the Throttle Position Sensor, start up the engine. If it stalls right away, turn the idling adjusting screw counter-clockwise until you can get the motor running at about 750rpm. You also might wanna rev it to about 2,000rpm a few times and let it come back to idle to see if it will stay at 750rpm. If it does, shut off the engine and connect the TPS. Done."

              Going to give that a try tomorrow.

              FRSport sells new SR IACV's. "ONLY" $175.

              I did the whole revving and disconnecting the TPS while I was setting my timing, I didn't know I had to to that for the idle as well.

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              • #8
                I'm thinking the IACV more than vacuum right now, primarily because it stumbles over itself so much that nearly stalls out. When I give it gas, it sometimes holds the rpms at 3k for a few seconds.

                Plus simply adjusting a screw to solve my problem is much easier than hunting down vacuum leaks.

                On a side note, going with this new IACV' I received the updated IACV with a metal adjusting screw instead of the oem plastic adjuster. I stripped that plastic adjuster in less than a 1/4 turn.

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                • #9
                  The deal with disconnecting the TPS is that it puts the ECU in idle adjust mode. This is the same mode that you'd be engaging with the Consult. In this mode it locks to the base timing angle so that you can easily set it. It also cuts off the IACV. So with the IACV, you just need to open the screw enough that it'll idle at a speed just under the target idle speed (usually 700rpms or so). That way the ECU controlled part of the IACV can add the rest of the air to hit the target.

                  So back out the IACV screw a lot. If it still stumbles you've got a vac leak. (technically, improper timing and fuel could also do this). Vac leak = dead lean = lean misfire = stumble.
                  She's built like a Steakhouse, but she handles like a Bistro.

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                  • #10
                    Chris briefly touched on this, but if your timing (had my distributor off) is to low the car won't idle to well. I just dealt with this 3 weeks ago and spent way to much time cranking on the IACV adjuster.
                    -Monty

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                    • #11
                      Originally posted by Bumnah View Post
                      I cracked opened my FSM on how to adjust the IACV, the steps were written if you had Consult on hand. I was in the EF&EC section. I'll take a closer look in a bit.
                      The section for doing it without Consult is usually right after the Consult section. keep flipping pages.
                      Originally posted by SoSideways
                      I don't care what color they are as long as they are LONG AND HARD.
                      '04 G35 Sedan 6MT- The DD
                      '96 240SX- The Track Toy

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                      • #12
                        How do i do it with consult? I just got consult usb cable actually...
                        "hexa-dodecahedron-triple-threaded-super-eleventy-way-adjustment-spec" dampers. -Def

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                        • #13
                          So I made some head way on the car.

                          01. My motor was not grounded. The cable that goes to the manifold wasn't connected to the manifold. So I had to ground out the. I put on a mini skirt shaved my legs, and went to the local audio installation shops to sweet talk someone there to give me one of their throw away cables from an amp install or something. Sure enough, the sight of a big Indian man in a mini skirt scared them into giving me what i wanted for free.

                          Grounding the motor def. helped.

                          Finally got the car to warm up enough to where it would idle on it's own for a moment. Ran in front of the car and kept it alive by manually controlling the tb.

                          I see smoking coming out of the #3 fuel injector. It looks not to be seated properly. I'm going to play with it tonight and see where I get with that. That injector gave me issues during install as well.

                          On a positive note, I haven't seen a single drop of fluid from any where. All oil and coolant points I opened, I reinstalled properly. So far so good...

                          Hopefully I make it to the event on Friday. It would sure suck to miss that.

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                          • #14
                            Glad the ground solved the problem (mostly).

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