I'm at my wits end trying to figure this one out.
Hoping someone here has seen something similar and could point me in the right direction
99 gmc sierra, 5.3, small cam, 3k converter.
Backstory:
A few years ago, swapped the cam then shortly after drop on a "TBSS" intake manifold and a cheapo fitech throttle body.
Soon after had very intermittent shifting issues at the dragstrip.
In recent times it's become more frequent and since I'm a bracket racer it's lost me three races this past weekend.
Hopefully I uploaded the log correctly. I've logged a bunch of trans parameters in the channels.
Scroll along to the 1:14 minute mark
Footbraking to 2100 rpm, mash the pedal and in the channels column, trans shift mode doesn't change state from "normal shift" to "normal shift wot" like normal passes. The truck proceeds to shift into 2nd almost immediately out of the hole, falls on it's face, then pcm must realize it's in the wrong gear, drops back to 1st and trans shift mode changes state to to normal shift WOT. The truck performs normally 99% of the time.
My questions are,
Is this something stupid obvious? I can't believe it's a shift MPH issue otherwise it would be constant.
What dictates the values in Trans Shift Mode?
Why does it not realize it's WOT when the TPS reads 100% , the TPS voltage is adequate I believe.
I've heard issues about the cheap throttle bodies and had a hell of a time tuning idle, but not sure how it could affect WOT. I've swapped in several different TPS sensors OEM ones.
Maybe a timing thing, where throttle has to be > 70% (as per the tune) for some time to go to "Normal Shift WOT", and that time you don't have access to changing. Maybe drop the 70% requirement to 20% or something small and repeat what you did (brake stand) and see if Shift Mode changes to Normal Shift WOT sooner/while not moving.
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