06 TBSS Low throttle return to idle issue

[Sleeper-6]

OK, Here's the rundown.

06 Trailblazer SS, e40 ECM running closed loop speed density.
Original LS2 Block, Stroked to 403
AFR 220 Heads
NW 103 TB
LSXRT Manifold
AR Long tubes with cats into a single 4" exhaust
GP Tuning Custom cam 232/240 .627/.616, 114* LSA, 8* Overlap
3200-3400 Circle D Converter

Overall the truck starts idles and drives well with one really annoying quirk. It will die when holding very light throttle or upon returning to idle from a light throttle position. Attached is a log and the tune file. Most of it is just driving around, near the end I duplicated the problem a few times, in park and drive. Especially noticeable in park is the commanded throttle position dropping off while I hold the throttle pedal steady. Same thing in drive, once you let off the pedal it closes too far and can't recover quick enough. I'm hoping that's pointing toward the problem, I just don't know how to fix it.

[kevin87turbot]

Your ETC Area Scalar is still calibrated for a stock throttle body. Here's a link for you...

https://forum.hptuners.com/showthrea...le-Body-scalar

[Sleeper-6]

I originally had the scalar adjusted up and it wouldn't start or idle worth a crap. I believe that's the post I read while doing my initial research, particularly #11. I dropped it back to stock and instantly things came around. I'm wondering if there's some exponential built into the TB itself to simulate stock type opening in the beginning of the butterfly rotation.

Found more info here https://forum.hptuners.com/showthrea...02mm-(not-LTx)

[kevin87turbot]

That's interesting. What happens if you reduce it lower than stock?

[Sleeper-6]

I haven't gone there yet. I figured it was pretty close since everything else seems to be behaving., Normal driving, idle, startup, etc. It's almost as if something is trying to adjust the idle back down when there's light steady pressure on the pedal and that throws everything off when I release it. Maybe in the adaptive idle settings somewhere? I'm not really sure.

Side note....Your screen name looks awfully familiar. TB.com?

[smokeshow]

Looks like you're missing a lot of definitions in the file...unless my HPT version is way too old..

[Lakegoat]

What does your MAP sensor read at key on--engine off?
Also, I was running a 102 NW and I had my ETC Scalar set at 7380.0000--ran perfect. Similar cam, similar converter, SD. I had to retune when I added the 102, but nothing much except a VE cleanup and Base running airflow.
Dynamic Air disable should be 8000 and reenable 7900---doesn't have anything to do with idle---but.
Engine Diagnostics---Airflow, make maf fail 0 and 1 or 0 and 0. Yeah I know, channels says maf is failed.
I would try 19 or 20 degrees of idle base timing and see if that helps. Leave coastdown alone.
In your overspeed/underspeed tables, where Overspeed is -20, make those cells -9 in PN and IN GEAR.
Where Underspeed is 13, make those cells 5 in PN and GEAR.
Make sure and keep a copy of your previous file before you do all that.
I you changed your ETC also, you will need to adjust your VE for sure.

[07GTS]

yea i think that idle torque follower table would be handy for this one, or have to adjust the VTT to suit the camshaft

[blindsquirrel]

E40 is airflow-based like the Gen3s, it's never going to have any of that torque-based stuff.

[07GTS]

E40 is airflow-based like the Gen3s, it's never going to have any of that torque-based stuff.

damn keep forgetting its the odd ball ecu missing alot of stuff

[blindsquirrel]

Well it's not that it's missing anything, it's just that circa-2005, the tq-based stuff didn't exist in the wild yet. It's different enough from the other Gen3s that it got its own category before the others showed up. If you were to look back at everything now you'd definitely call it a Gen3 and save the Gen4 label for the true torque based ECMs.

[Sleeper-6]

What does your MAP sensor read at key on--engine off?
Also, I was running a 102 NW and I had my ETC Scalar set at 7380.0000--ran perfect. Similar cam, similar converter, SD. I had to retune when I added the 102, but nothing much except a VE cleanup and Base running airflow.
Dynamic Air disable should be 8000 and reenable 7900---doesn't have anything to do with idle---but.
Engine Diagnostics---Airflow, make maf fail 0 and 1 or 0 and 0. Yeah I know, channels says maf is failed.
I would try 19 or 20 degrees of idle base timing and see if that helps. Leave coastdown alone.
In your overspeed/underspeed tables, where Overspeed is -20, make those cells -9 in PN and IN GEAR.
Where Underspeed is 13, make those cells 5 in PN and GEAR.
Make sure and keep a copy of your previous file before you do all that.
I you changed your ETC also, you will need to adjust your VE for sure.

Thanks, I'll check that MAP reading and give these changes a shot tomorrow after work. I did have the ETC up around there and it wouldn't run for squat. Something is significantly different between the NW102 and NW103 throttle body. Everything I'm reading is saying leave the ETC around stock or even slightly below for the 103MM piece.

It really seems like the ECM is not recognize that very light throttle isn't idle. Under steady very light throttle it tries to close the butterfly to return the truck to idle, lift off the pedal once that happens and it will die.

[eXo3901]

FWIW, with the E40 I have noticed anything in the airflow tab that is throttle/idle related tends to take a few drive cycles to settle down. A scaled tuned also messes with the idle stuff. There are throttle follower tables that are not defined in HPT, not sure if they do anything in the E40 though I have not tested.