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Thread: LQ4 lean on start up.

  1. #11
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    Okay, I guess your wideband is working.

    I don't know why your fueling would be so far out. If you have the equipment, you could check your fuel pressure at the rail. The only other thing I could suggest is for you to tune your idle using your fuel trims and then see if the next cold start goes lean.

  2. #12
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    Quote Originally Posted by statesman View Post
    Okay, I guess your wideband is working.

    I don't know why your fueling would be so far out. You could check your fuel pressure at the rail if you have the equipment. The only other thing I could suggest is for you to tune your idle using your fuel trims and then see if the next cold start goes lean.
    I checked the fuel rail pressure without a vacuum and got 58PSI. I ran the car yesterday, and warm starts worked flawlessly, idling at 15 AFR. So, once the vehicle warms, the problem goes. The problem is in the open loop until the closed loop kicks in. LTFTs add up to 25% to sustain around 15 AFR when idling. I used a stock VE+MAF table and added 20%. Could my VE and MAF be that far out?

    I do have a CALC Vet log taken at idle. I will see what that table is trying to add.

  3. #13
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    Quote Originally Posted by pormgb View Post
    I used a stock VE+MAF table and added 20%. Could my VE and MAF be that far out?
    That's highly unlikely. If you have a stock MAF sensor, then the stock MAF curve should be fairly close. I would adjust the IFR table until you get reasonably good fueling with the stock MAF curve.

  4. #14
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    Quote Originally Posted by statesman View Post
    That's highly unlikely. If you have a stock MAF sensor, the stock MAF curve should be close. I would adjust the IFR table until you get reasonably good fueling with the stock MAF curve.
    I removed 5% from the IFR table, and the startup AFRs improved. When the motor starts, it's around 13AFR, then creeps up to around 17 (with IFR changes). The first cold start idles very low, around 500rpm, until the motor begins to warm up, and restarts are perfect. Even with the IFR changes, the LTFTs are around +25%. I also removed the vacuum reference from the FPR, so there is a constant 58 PSI.

  5. #15
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    Quote Originally Posted by pormgb View Post
    I removed 5% from the IFR table, and the startup AFRs improved. When the motor starts, it's around 13AFR, then creeps up to around 17 (with IFR changes).
    Take another 4% or 5% out of the IFR table. You're still a bit too lean now.


    Quote Originally Posted by pormgb View Post
    I also removed the vacuum reference from the FPR, so there is a constant 58 PSI.
    If you do that, you'll have to slope your IFR table. Don't drive the car until you do that.... or if you like the flat IFR table, then reconnect the vacuum reference.

  6. #16
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    Quote Originally Posted by statesman View Post
    Take another 4% or 5% out of the IFR table. You're still a bit too lean now.




    If you do that, you'll have to slope your IFR table. Don't drive the car until you do that.... or if you like the flat IFR table, then reconnect the vacuum reference.
    The IFR is sloped, and here is what I have prior to removing another 5%.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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