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Thread: Stock Staying in "CL - Normal" at WOT

  1. #1
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    Stock Staying in "CL - Normal" at WOT

    I have a 2006 Silverado 2500HD LQ4 6.0L. I found this problem when trouble shooting my lean condition at WOT which was the fuel filter so I had to replace the fuel pump assembly.

    The system will still go into OL when it is in DFCO or during a cold start. But I can not get it to go into OL at WOT so it is not doing the Power Enrichment either. Here are some of the Specs from the data log which from what I gather they all point to say it should go into OL

    @WOT 4473rpm
    Manifold Absolute Pressure 96.0KPA
    Mass Air Flow 233.95g/sec
    Throttle Position 100%
    Manifold Vacuum 0.39psi
    Intake Air Temp 64deg
    Coolant Temp 199deg
    Calculated Load 91%
    Fuel Trim Cell 15
    Delivered Engine Torque 349ftlb
    Dynamic Cylinder Air 0.79g/cyl

    Fuel System Status CL - Normal
    Air Fuel Ratio Commanded 14.68


    The truck is stock and the tune on my LQ9 Jeep YJ goes in OL just fine so I compared the Tunes and do not find differences in any place that would cause this.

    Any ideas? Thanks

  2. #2
    Trucks have a PE delay if RPM is below 5500. How long are you holding WOT?

  3. #3
    Senior Tuner LSxpwrdZ's Avatar
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    This is normal on most v8 trucks.... this is why they pick up so much from only a tune in my experience! It's funny to, when you richen it up under load it actually ends up getting greater fuel economy because your not putting the engine under nearly as much strain because the engine generates more power/torque and requires the engine to not work as hard.
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    Your right the delay is set to 5500rpm and the truck has shifted by 5450 or so. The funny thing is that my Jeep LQ9 is also set to 5500rpm but it goes OL - accel/decel as soon as I stomp it which in a log I have up it is at 1977rpm 78%TPS and 33%load, this snap shot is as I am stomping down on it and it just switched from CL - Normal.

    This makes my question as to why the LQ9 goes OL and richens to my commanded 13:1 so easy but the truck wont. Also I dont understand why GM would want the thing running 14.68:1 under heavy load and throttle....

  5. #5
    Senior Tuner Higgs Boson's Avatar
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    You sure it's OL and not just the OLFA table commanding richer?

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    I am sure. I dialed these in with the wideband on the EQ ratio vs. RPM. And I am logging the "Fuel system status" which is where I am getting the OL status. I would have thought it would also tell me when it went into Power Enrichment.

    It does act like the LQ9 program does not care about the Delay RPM since it is set at 5500rpm like the LQ4 but ignores it. I do know that it cares about the MAP threshold though because I have disabled it before to tune the VE table.

    This is why I dont get that the LQ4 does not play the same way.

  7. #7
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    If it is indeed not going into open loop at WOT,put 0 under all tabs under power enrichment pe enable.That is common with a few 06 Os's
    Do that and report back
    Last edited by vortec; 11-05-2010 at 05:51 AM.

  8. #8
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    Thanks vortec
    It is going into OL PE mode now. It does take about 95% throttle or more to get it to change states though. I would think GM would make an updated OS for these vehicles to fix a problem like this as I would think that it could cause damage by not richening up at WOT.

    So I am guessing that this is the fix for vehicles like mine? I do get better torque now as I can feel it plus the "delivered Engine Torque" has gone from like 365 to 394 now. These are more comparison numbers as I know it is not accurate and they were not pulled from 3rd gear

    I figure My lQ9 is at about 410 torque with headers, exhaust, and a tune and that is about what the hp tuner log shows. All I have done to this LQ4 is adjust timing a little but AFR is still the stock way rich PE mode. 0-60 with this 3/4ton is now 9sec and my jeep LQ9 being lighter and a tad more power is just under 6sec
    Last edited by Dominatorstang; 11-05-2010 at 07:55 PM.

  9. #9
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    Adjust your PE Enable TPS table. The 05 file I have its 90% across the board.
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  10. #10
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    that makes sense then as mine are the same. I wonder why my LQ9 goes into PE even before the set 5500rpm delay and at 78%TPS or maybe even lower TPS but that is what i got from my log. The LQ9 settings are also set at 90%

  11. #11
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    Good to see it worked for you.I see people chasing this often.

  12. #12
    Senior Tuner Frost's Avatar
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    The delays are non-functional in car cals and work in the truck cals. That is the difference that you guys have seen.
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  13. #13
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    Correct
    Quote Originally Posted by Frost View Post
    The delays are non-functional in car cals and work in the truck cals. That is the difference that you guys have seen.
    Last edited by vortec; 11-06-2010 at 01:23 AM.

  14. #14
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    I am with you guys then, my LQ9 programming is from a 02 escalade so SUV's and cars ignore most of the settings on PE but they must still use the MAP value delay as I have disabled PE with this for tuning. And trucks use all of the delays listed.

    So I wonder if i should just 0 out everything except the MAP and MAP hyst, to try and make it work more like the cars
    Last edited by Dominatorstang; 11-06-2010 at 12:30 PM.