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Thread: 1986 IROC with ZZ4 350

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    Fuel Injected! ZEDRATED's Avatar
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    1986 IROC with ZZ4 350

    So I am starting a new thread, I replaced my Accel 30lb injectors with a set of Bosch3's 24lb injectors and what I am finding is that when the car goes into closed loop it get's really lean. 17-19:1.
    It was doing the same thing with the 30lb injectors. I checked continuity from the O2 sensor connector to the computer and it was ok and I just replaced my 1 year old NGK O2 sensor with a Delco one and yet the same thing. I got all the little exhuast leaks fixed up as well, I made a copper gasket at work and used some aircraft grade gasket material. Worked like a charm:
    Do you guys think the 24lb injectors are big enough for my set up?
    350 ZZ4 with GM hot cam and TPIS miniram.
    Any ideas why the O2 sensor is making it go lean???
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    Last edited by ZEDRATED; 09-28-2013 at 12:02 AM.

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    Fuel Injected! JeepsAndGuns's Avatar
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    I am running those exact injectors in my AMC 401. I'm running them at 45 psi and have plenty of fuel. I had to reduce my fuel tables down a good bit when I went to MPFI from TBI.
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

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    What is your exact combination besides the miniram? Specs on that hotcam? What heads and cr? What does the exhaust system consist of? Those injectors should be enough. Accel anything is pretty much garbage. Good to get rid of their injectors. What wideband are you using? Does the zz4 have the 58cc l98 aluminum heads on it?
    Last edited by S10LS; 09-28-2013 at 02:58 AM.

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    LT4 hot cam: http://www.eecis.udel.edu/~davis/z28/buildup/cam/
    10:1 compression, aluminum heads, ZZ4 crate motor:http://www.chevroletperformance.com/...9712&engCat=sb
    hedman short headers with no cat and I'm using AEM AFR guage.
    Fuel pressure set to 44 psi. Maybe I need it higher?

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    So any reason why on idle my WBO2 sensor keeps going max lean?
    Could it possible be an ECM problem? The NBO2 sensor is brand new and continuity from the sensor to the computer is good?

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    Exhaust flow over the sensor. WB's dont do the greatest at idle.

    peace
    Hog

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    Quote Originally Posted by Hog View Post
    Exhaust flow over the sensor. WB's dont do the greatest at idle.

    peace
    Hog
    I have to disagree, when I burn a chip to stay in open loop the AFR is close to 14.7 on idle.
    Last edited by ZEDRATED; 10-11-2013 at 03:35 AM.

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    if it is staying 14.7 at idle where is it lean?

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    Sorry, my mistake. When I burn a chip to stay in open loop it stays near stoich near 14.7, as soon as it goes into closed loop when I enable it it then goes max lean.

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    Could the ECM have a problem?

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    I think what hog said is whats happening. most bins are 13.5 in open loop if your getting 14.7 even in open loop at idle your flow across the sensor is not enough to read 13.5 if that is what your bin is set at in open loop.

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    It kinda makes sense but it's not like it is going to 16 or 17 in closed loop, it gradually goes all the way and max's out the guage. Also, I can feel it hesitate when I give it some light throttle and run rought as opposed to when I burn a bin to stay in open loop so I don't think the gauge is lieing. Is there any other possibilities? I have a cousin with the exact same WBO2 sensor on his Subaru and he has no issues with a good reading on idle. I actually can't remember the exact number when I left it in open loop but I think was under 14.

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    it sounds like the afr is moving the same in open loop and closed loop idle like hog said lack of exhast flow, I don't know about the ecm that you have as far as adjusting the bin file, it sounds like the pump shot fuel increase is off , may be eagle mark or six shooter will be on here on a little while, they know about pump shots.

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    Quote Originally Posted by ZEDRATED View Post
    So I am starting a new thread, I replaced my Accel 30lb injectors with a set of Bosch3's 24lb injectors and what I am finding is that when the car goes into closed loop it get's really lean. 17-19:1.
    It was doing the same thing with the 30lb injectors.
    Did you install the Injector Offsets that came with new injectors?

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

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    John at FIC said to just use the stock numbers and it wouldn't affect it much or And to just change the constant to 24.
    I bought the injectors off him. He said he doesn't have correction for them and maybe they will be the same as ford's.
    Also, is 43.5 psi enough? I think I would need a little more pressure???

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