IACV/Air Regulator brand new but doesn’t open at the right time?

Discussion in 'Z32 Technical' started by tjleilo, Apr 10, 2019.

  1. tjleilo

    tjleilo New Member

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    I installed a new iacv and air regulator two months ago and it hasn’t seemed to do anything. Upon looking through Conzult my iacv is only 15% open at idle and the idle is low and the car shakes and runs rich, as I accelerate and give the car more gas the iacv opens more and opens to 49% and stays there. This doesn’t seem normal. My car seems to think that since the iacv is open that it has a vacuum leak as it richens the fuel mixture to compensate for this it seems like. Is this normal for the IACV to open at these times, if not, do you know how I would fix it?
     
  2. tjleilo

    tjleilo New Member

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    Update: The car runs lean at 2,100 rpm. It doesn’t fluctuate up or down it runs lean constantly if I reset the computer self learning. Indebted I reset the computer self learning it stays constantly at lean at 2,100 rpm.
     
  3. Martin Williams

    Martin Williams Active Member

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    How did you set the manual air screw on IACV? Did you disconnect the TPS when allowing computer to reset idle? Just check that you haven't mixed up the plugs for IACV and A/C compensation solenoids. The 300zx manual gives good procedure for setting up IACV
     
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  4. tjleilo

    tjleilo New Member

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    I disconnected the TPS and I also put the car in the idle adjust mode on conzult as well. I set it to be at 720rpm while I’m neutral as I have a non turbo auto.
    Thank you for your reply! I’ll look into that!
     
  5. Fists

    Fists Well-Known Member

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    The IACV should be drawing air from one of the intake pipes so it's all measured by the air flow meter, when installed properly it wont create a vacuum leak.

    Fuel mixtures should be rich when accelerating or going up hill and should go into open loop using the O2 sensors to keep mixtures about even when cruising.
     
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  6. tjleilo

    tjleilo New Member

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    Thanks! So while I give the car gas the idle air control valve should be open based on throttle position as well? When I’m at full open throttle or very aggressive acceleration the fuel mixture leans out a lot. I’m assuming this isn’t right and could be part of my performance problem...?
     
  7. rob260

    rob260 Moderator Staff Member

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    How did you determine that the original unit was faulty?
     
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  8. tjleilo

    tjleilo New Member

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    The old one was 25 years old and was rusted out on the inside, decided it was a good part to replace since I was having idling issues. When I looked inside there was so much rust and carbon build up. Replaced all of the hoses with silicone hoses too. The car leans out under heavy acceleration so I’m wondering if my pump has some play in this.
     
  9. rob260

    rob260 Moderator Staff Member

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    How lean is lean and what are you measuring with?
     
  10. tjleilo

    tjleilo New Member

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    I’m just measuring with ConZult based off of the short term trim and long term trim values and the alpha a/f it starts to drop to around 94% really quickly on just a very short pull from 104%. Ive had suspicions about my pump for a while. I’m new to using ConZult.
     
  11. tjleilo

    tjleilo New Member

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    When it “leans” out the car rattled and shakes pretty hard as well. I don’t have any vacuum leaks, fuel leaks, etc. Fuel injectors and spark plugs were just replaced to. Oxygen sensors have been checked.
     
  12. Fists

    Fists Well-Known Member

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    I'm not very familiar with the readings in conzult or how the trim works specifically but a lean reading at the O2 sensors can also be caused by an ignition mis-fire (spark plug, coil pack, igniter/ptu) because they just read the unburnt oxygen and have no idea whether the rest of the gas passing by is raw fuel or CO2.

    The fuel filter is also a possibility but it will be very dependent on engine load, the faster you're going/harder you're accelerating it will get worse but revving in neutral wont be effected much, spark plug and coilpack problems can also be load dependent. There is also a pre-filter on the fuel pump in the tank that can blocked up, sometimes the pre-filter can block intermittently as debris swirls around the tank and then settles to the bottom again once the pump turns off.

    Aside from all that the majority of people who say "I don't have any vacuum leaks" end up eventually realising they have a big ol' leak. The accordion hoses like to crack on the under side where you don't notice it and an incorrectly installed vented oil catch can or other PCV mods can lead to vac leaks.
     
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  13. tjleilo

    tjleilo New Member

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    Dang, good info! Thank you for taking the time out to help me, greatly appeeciated! I didn’t know of the filter in tank. I’m going on there soon to check out the fuel hoses and to see what condition they are in. Thank you again so much for all of your help! I bought some vacuum line the other day too so I’ll go back around and check.
    Thank you again for your help!
     

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