RADustin
February 13th, 2017, 04:39 AM
Working on my brothers truck. It's the thread title swapped in a '67 GMC.
Currently- 4.8L/DBW/1MB/4L80/12592618 OS
Pedal and tac are 2005. Motor/PCM was originally 2007 classic. Swapped tac when we changed OS.
The truck revs really strange(slow) and makes no power driving it around. If I tip in the throttle quickly(snap it open and let it shut), but only to 30-40% absolute, it will jump to 100% commanded on the tech2 and snap back. If I tip it slowly it will slowly climb and seems ok.
Getting no codes, no reduced power. Scanned with tech2, everything 'looks' OK.
Mentionables-
-Idle TPS seems high. about 12-14%.
-Idle airflow seems ok- about 8-12g/s depending on temp. reading from MAF. VE has not been tuned.
-CASE relearn is complete and seems OK.
-Startup airflow is not working. No matter how much I add in startup friction and startup correction, it does not flare on start up but rather stumbles to life.
Questions so far-
-How is startup throttle blade position calculated? Why can't I get the engine to roar to life like I can my other ls1 with too much startup airflow? When I command say 12g/s on startup, basically how does the engine set the blade to get this amount of air? I imagine it uses cranking VE maybe with MAP and IAC info???
-Has anyone experienced this? Is it probably trans related or engine?
Just really messing with my head- I can only imagine it is a physical problem with the engine/trans or the pedal/tac/OS relationship is off.
Next we are going to flash in a stock tune file from a 6.0/4L80 with the same OS. See how that works. Basically I think the plan is to keep going backwards eventually to the original tune that last ran on the truck, even if we have to swap back to a different OS and tac module. Just want to ensure nothing is physically wrong with the truck before we assume it all to be electronics. Then once we verify that it is just the pedal/tac/OS/tune file issue we will have to narrow it down from there.
Any ideas? Suggestions?
Currently- 4.8L/DBW/1MB/4L80/12592618 OS
Pedal and tac are 2005. Motor/PCM was originally 2007 classic. Swapped tac when we changed OS.
The truck revs really strange(slow) and makes no power driving it around. If I tip in the throttle quickly(snap it open and let it shut), but only to 30-40% absolute, it will jump to 100% commanded on the tech2 and snap back. If I tip it slowly it will slowly climb and seems ok.
Getting no codes, no reduced power. Scanned with tech2, everything 'looks' OK.
Mentionables-
-Idle TPS seems high. about 12-14%.
-Idle airflow seems ok- about 8-12g/s depending on temp. reading from MAF. VE has not been tuned.
-CASE relearn is complete and seems OK.
-Startup airflow is not working. No matter how much I add in startup friction and startup correction, it does not flare on start up but rather stumbles to life.
Questions so far-
-How is startup throttle blade position calculated? Why can't I get the engine to roar to life like I can my other ls1 with too much startup airflow? When I command say 12g/s on startup, basically how does the engine set the blade to get this amount of air? I imagine it uses cranking VE maybe with MAP and IAC info???
-Has anyone experienced this? Is it probably trans related or engine?
Just really messing with my head- I can only imagine it is a physical problem with the engine/trans or the pedal/tac/OS relationship is off.
Next we are going to flash in a stock tune file from a 6.0/4L80 with the same OS. See how that works. Basically I think the plan is to keep going backwards eventually to the original tune that last ran on the truck, even if we have to swap back to a different OS and tac module. Just want to ensure nothing is physically wrong with the truck before we assume it all to be electronics. Then once we verify that it is just the pedal/tac/OS/tune file issue we will have to narrow it down from there.
Any ideas? Suggestions?