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Thread: Stumped! Please help if you can

  1. #1
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    Stumped! Please help if you can

    Im working on doing a MAF/SD tune on a bit of a frankenstein car. Its a 68 Camaro with an 08 Escalade L92 engine. The cam is an unknown aftermarket piece that seems by idle characteristics to be fairly large and is equipped with a mechanical timing limiter. The intake manifold is off of a 10 camaro, and it has an LS2 MAF.

    Ive got the idle, and cruise portions of the MAF tuned just where I want them.. Im now working on the PE and such for WOT. I was getting a strange surge/cycling under WOT when I first started and it was really lean. I went ahead and put ALOT of fuel in the PE table to get it at least safe so I could back down to the AFR I wanted...

    Now the surge/cycling issue is huge. It makes a noticeable difference in sound, power/torque output and even seems to make the AFR's jump around..

    This cycling seems to affect EVERYTHING Im logging. Ive tried disabling the knock sensors (didnt make a difference) so I went ahead and disabled the Burst knock and it stopped showing knock retard on the logs but didnt seem to help with my issue.

    It if it werent for fuel responding to the PE changes, Id swear it was bouncing in and out of PE mode.

    Anyway, heres the files, please let me know if you can shed some light on this issue.

  2. #2
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    Ive had it suggested that there may be an incompatability with the hardware involved. i.e. Electronic pedal, Throttle body, and VCM... Im gathering part numbers off of the components but Im told by the owner that he 'thinks' the Throttle body is off of the same escalade that the engine and VCM were sourced from. But there's a possibility that the throttle body is off an LS3 car..

    The pedal on the other hand, Im just starting to dig under the dash
    Last edited by PST; 05-20-2011 at 09:18 AM.

  3. #3
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    FWIW, I went ahead and attempted lowering the values in the Engine > Airflow > Electronic Throttle > Desired Throttle Area tables and it seems to have made the problem more erratic. It did lower the peak throttle percent to 20% less than what I commanded in the tables, but almost looks like the bouncing off of full throttle got faster..

    To recap my problem... As soon as I go WOT, the readings of MAF, MAP, TPS, and Advance all start oscillating up and down.

    I have tried smoothing the timing tables, confirmed that it is not detonating, and now tried limiting the throttle opening percent. All to no avail.. Fuel is safe, and timing is very moderate. I cannot find any table in the software that will let me have any affect on this problem...

  4. #4
    Senior Tuner DSteck's Avatar
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    Try a throttle body and gas pedal from the same vehicle the pcm is from. Looks like the throttle body going nuts is driving the rest.

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  5. #5
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    Yeah, thats about were Im at with it... Looks like the GM pedal assembly isnt too costly, but making an escalade pedal work in a 68 camaro is gonna be fun.

    Thanks for your input though. It's nice to see someone else having a similar view based on the data presented.

  6. #6
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    So, the APP stuff is only showing the throttle going to 75%. However, its still commanding 97% via my ETC tables.

    All my APP data is stead, the ETC stuff bounces. We have an oe truck pedal on the way, but Im getting this strange feeling there is some sort of limiter coming into play. I think I have them all turned off completely at the moment.

    Could someone please review this tune file and let me know if they see ANYTHING that could be acting as a limiter and I have not already disabled?

    Its worth noting that this problem is only occuring on the dyno. If I put it on the road, the curves all look nice and smooth.

  7. #7
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    Holy crap! I found more stuff that seemed like it might be limiting me... Disabled them, made a pull and got a clean no nonsense pull out of it finally!

    Unfortunately, subsequent pulls did not go so smoothly :/

    Here's the log and the current tune file:

  8. #8
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    NOw for the subsequent pull log... Im seeing that my inputs are remaining steady... But for some reason my desired ETC starts to bounce, along with everything else. What Im seeing now though that Ive never seen before (because I want logging it) is that when the desired ETC position drops, "Spark TqMgt Type" switches from "None" to "Trans"...

    Im not seeing any other limiter there... Anyone have any ideas?

  9. #9
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    Seems this 'freak' of a car has a T42 TCM in place of what would be a T43 if it were ALL swapped from an 08 Escalade. Apparently this was done so that the car could run a 4L70 transmission instead of the 6L80.

    So when I look at the files with HpTuners, Im seeing E38 engine controls and T42 transmission controls. Somewhere in this mess is a torque limiter that is being requested by the T42 TCM that HpTuners is not allowing access to. What a nightmare :/

  10. #10
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    Has any one figured this out yet because i am having the same issues. and i have the same T42 Transmission