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Thread: Absolutely bizzare problem

  1. #1
    Potential Tuner
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    Jul 2019
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    Absolutely bizzare problem

    This one has me and my tuner scratching our heads, 2011 Z06 LS7 have mild cam Cam Motion stage one, MSD intake long tube tri Y headers, cats with rear O2 disconnected and Halltech killer bee. Car makes 568hp and 535T at the rear wheels runs great under full power, and runs fine on hot days, at night going home go from about 500' elevation and drop down to sea level and close to water and the temp goes outside temp drops to about 15C from say 20C the car goes lean on passenger side bank only as in 17-18-1. I have 2 wide bands in the car drivers side shows 14.5-15 passenger side goes to 18 and then off the gauge car starts running rough check engine light comes on and codes show multiple lean cylinder misfires. Shut off run codes clear check engine and it goes back to okay, so tried running it in open loop by disconnecting the O2 from the cats still does the same thing, checked for vacuum leaks at manifold with ether and nothing, pulls 18+ vacuum at part throttle in open loop. In closed loop mode with HP tuners scan hooked up something in the software is telling just the passenger bank to go lean in open loop it will go richer on acceleration only, shows 12-13 on the wide bands. Cruising around in open loop passenger side is 1-1.5 leaner than drivers side all the time except on startup then it runs 12-13-1 on both banks and tracks within .1 to .3 of each other then after the 2 minute initial start passenger side runs leaner 1-1.5 again. Tried 2 different sets of injectors, different MAP sensors, same thing. How is this possible. We have not done any virtual VE tuning yet those tables in HP tuners are blank.

    Is there some hidden part of the software that allows adjustments from bank to bank in the tune or is this a problem in the ECU itself.

    Another thought I had in the middle of the night is it something to do with EVAP purge as that goes into the intake at the front by the #2 cylinder intake trumpet
    Last edited by G8Pumpkin; 07-20-2019 at 01:45 PM.

  2. #2
    Tuner in Training 1278342005's Avatar
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    Have you tried switching upstream O2 sensors to see if it switches sides? It may have something to do with your O2 heaters. I've had 5th Gen Camaro's do something very similar for no reason. Switched o2 sides and it switched with it. Just because the O2 is sensing properly doesn't mean that if it gets into lower temperatures that it will continue to function properly. They have to work at a certain temp or they just don't work right. Just a thought.

  3. #3
    Drop it into open loop and see if it straightens out

  4. #4
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    Found the problem it is being caused by the EVAP system dumping fuel into the intake in front of the #2 cylinder intake Trumpet. Temporarily I have the EVAP venting outside the engine compartment until I come up with a more permanent solution, and myself and my tuner are about to go down the road of learning and tuning the VE tables. Also looked at the stock intake VS the MSD and there is a difference its not huge but it all adds up the stock passage goes side ways to the opening right behind the throttle blade VS the MSD going back towards #2 cylinder also the EVAP solenoid has failed again this is the second one in 2 years which is one of the reasons I was not looking closely in that area.

  5. #5
    Advanced Tuner IARLLC's Avatar
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    The intake manifold should not matter. Evap should never have fuel in it, only vapor.

    I have seen this happen on a 2010 Suburban a few years ago. Somebody forgot to hook up the vent tube inside the gas tank when changing a fuel pump so whenever it had a really full gas tank it would suck fuel up the vapor hose and dump it in the front of the intake manifold causing it to die at every stop for the first few stops after a fill-up. Once I hooked up the vapor hose inside the tank...only vapor in the evap system.

    Solenoid failing from raw fuel in it?