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Discussion Starter #1 (Edited)
At slight throttle, the car will idle up, then drop rpms. In the log, from steady idle, I'll move the pedal to ~23%. Throttle responds, but after a couple of seconds, will start to fall, even though I'm keeping the pedal at ~23%. Commanded throttle drops for no reason that I can determine. WTF???
 

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Would be interesting to see the throttle blade in action...if its staying open with your foot still on or not. Weird indeed.
 

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Discussion Starter #3
If I command more throttle (like 28%), it will respond and stay, so this behavior only happens between ~22-26% throttle, and it is pretty consistent and repeatable. Already replaced the throttle body/cleaned MAF/new air filter, with no change in behavior.
 

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Might check the peddle output with a meter and see if it is falling off.
 

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Thought about that, but if that was the case, throttle position would drop in the log, but it doesn't.
TPS and accelerator position are two different channels Cheebs
 

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Something is off with your PIDs you are logging. At idle your pedal PID should read 0.


Capture.PNG
 

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Sorry, meant pedal position, not throttle position.



Pedal position SAE is % of pedal sensor voltage, I believe, so 0V=0%.
But in your whole log your pedal % never goes to 0. Did you always have your foot on the gas?
 

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What are your mods? Just looked at the tune, why is your ETC scalar at 4936? Stock is 5060.
 

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Discussion Starter #11
What are your mods? Just looked at the tune, why is your ETC scalar at 4936? Stock is 5060.
I was running a 90mm TB, but put the stock one back on while trying to troubleshoot the problem. ETC scalar was 5936; I knew stock was around 5K so I just subtracted 1K (was running late for work, didn't have time to look it up). LS9 cam, headers, pulley, 850lb injectors, nothing crazy.
 

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I would start with a stock tune and just change the injector info and see if it does it. A LS9 cam is not that aggressive so it should run at 23% throttle no problem.
 

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Discussion Starter #13
I would start with a stock tune and just change the injector info and see if it does it. A LS9 cam is not that aggressive so it should run at 23% throttle no problem.
And, just like that, the problem seems to have fixed itself. Did a throttle relearn after I swapped out the throttle body, then did another one after I swapped the 90mm back in, and all of a sudden, no problems. Sigh, I'm just going to keep my fingers crossed that it doesn't happen again. Hopefully it's not the throttle body going bad somehow.
 
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