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Thread: 2005 Envoy I6 Tuning issues

  1. #1
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    2005 Envoy I6 Tuning issues

    Hello, everyone. I'm having some issues with a 2005 Envoy 4.2 I6. Initially I was trying to find a throttle opening rate adjustment in the tuner software. Chad has told me that they are looking into whether or not that feature can be added. Currently the Envoy is VERY sluggish off the line with throttle response times of about 1.5 seconds.

    I'm also having some other issues. In lieu of retyping everything, I have copied an email that I sent to tech support below. Please read through it and if you have any insight whatsoever...to any of the issues...please share it with me. Thank you!

    "Thank you for your help and yes, my "view" is set to advanced. I've attached a copy of the stock tune file.

    I'm having another issue also. I tried raising the idle speed to 700 rpm vs. the stock speed of 613 rpm. When I do this, the engine surges. In park, at idle or when shifting into a gear (such as reverse), the engine will suddenly shoot up to around 1500 rpm (sometimes higher) and hang out there for a while. Then, all of a sudden, it will drop back to the approx. 700 rpm...this all happens with absolutely no throttle input from me. A few moments later, the cycle repeats. I even tried a calibration where Idle speed was the ONLY parameter that I changed from stock and the issue persists. I've attached a VCM Scanner log file that shows the events. In this tune I also have the base timing at idle reduced, fyi, because this engine detonates badly in gear at idle...weird I know. Anyways, you will see the surging while in neutral and then at 6:10:30 I shift into reverse and 20 seconds later I shift back into neutral and the rpm's skyrocket. This does not occur with the stock tune.

    This engine has 228,000 miles. New cylinder head about 3 yrs ago and a new OEM throttle body about 1.5 yrs ago (dealer installed due to high idle complaint, issue still remains, vehicle will idle itself all the way into 2nd gear (20 mph) with a tps% of 20%, then once it shifts into 2nd gear the tps% drops to about 9% and the truck slows down just enough to drop into 1st gear where the tps% jumps back up to 20% thus repeating the cycle) and the above all happens with the stock tune.

    I'm truly at a loss with this thing... I don't know if the MAP sensor could be driving these changes or if it's the throttle body or maybe the ECM that is commanding such strange operation. Any insight that you can provide would be much appreciated.

    One more thing regarding the "special functions" on the VCM Scanner software. So far the only items that actually function are the spark retard and the A/C clutch on/off command. None of the other special functions actually function. Maybe it's because I'm using a trial version. I was also hoping that I could do more advanced things such as activate the VVT and perhaps see the data that ECM is commanding such as commanded idle speed, VVT status, timing etc. That way I could determine what is actually being requested and not just seeing the results. Basically I'm wanting the functionality of a high dollar scan tool for a lot less money. haha...seriously though, are these options possible with your software? Seems like it should be readily available since the program is already communicating with the ECM but I'm not a software engineer...although I did work 10 yrs as an application engineer for Cummins, Inc. and we had a similar program called Insite that we used but it was a bit limited in functionality. We had to use CalTerm to make serious engine changes but I digress."

    Envoy log 3 mod 1 tps up and down on its own.hpl
    Envoy Stock - 700 rpm.hpt
    Envoy Stock.hpt

  2. #2
    Senior Tuner cobaltssoverbooster's Avatar
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    why is your timing advance always negative?
    2000 Ford Mustang - Top Sportsman

  3. #3
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    I had backed off the base timing in order to combat a severe detonation issue while idling in gear (reverse or drive). However, even when I tried a tune with the stock timing...where the only change that I made was to idle rpm...the surging problem still occurred.

  4. #4
    Senior Tuner cobaltssoverbooster's Avatar
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    in your scan file i see ignition is like -4 and as rpm increases it goes to like -16. its almost as if the channel isnt reporting correctly.
    if it is true then thats a fairly decent issue. idle advance for an ecotec is somewhere between 14-18* advance depending on what the motor desires.

    my 2.0 lnf idled at 18* and my cousins lsj idled at 16*
    im just really finding it odd that your scanner shows a constant negative, as if the channel was reading inverted signs.
    2000 Ford Mustang - Top Sportsman