Hanging Idle When Moving

Just got EFILive V1 this week and have been tweaking little bits at a time. I would like to tackle a hanging idle issue I have. My vehicle is an '01 Silverado 5.3L with a T56 swapped in. Running the stock OS with the 4L60E tune, with minor changes to remove trans DTC's.

As soon as the vehicle starts moving, I'd say over 2-3mph, the idle speed jumps up. The idle speed when moving depends slightly on the vehicle speed, but it ranges from 1000-1500RPM normally. For example, if I put it in neutral and coast off the freeway it will idle at 1500-1400RPM dropping slowly to ~1000RPM as I slow down. Once I come to a stop it will immediately drop to the correct idle speed of 650RPM. The issue is worse when cold. When coasting I'd prefer it to idle at 650RPM or a little higher (if the brake booster needs the vacuum). It would also make low-RPM shifting a lot easier. Revving from idle when stopped is fine, it will return in a reasonable amount of time.

My hunch says it has to do with idle settings, maybe the throttle cracker or decay rates? I zeroed out the stall saver as per the f-body T56 tune, but I don't think it's related.

Any tips are appreciated, thanks!

Ok first, do a seg swap to a manual OS that actually runs a T56 and report back. Running an auto OS with a manual trans = no no if you can avoid it (which you can very easily with EFILive).

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Originally Posted by ScarabEpic22

Ok first, do a seg swap to a manual OS that actually runs a T56 and report back. Running an auto OS with a manual trans = no no if you can avoid it (which you can very easily with EFILive).

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Why does it matter if I'm running an auto segment with the T56? As long as all of the settings are correct the PCM shouldn't care, right? The PCM thinks it's in 2nd all the time so it never uses the P/N settings. The torque management is all disabled. And the A4 trans DTC's have been switched off.

My OS (12208322) never came in a manual, and EFILive won't let me load a different OS to do the segment swap.

Is there more to a "segment" than the settings visible in the tune tool?

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Originally Posted by ferocity02

Why does it matter if I'm running an auto segment with the T56? As long as all of the settings are correct the PCM shouldn't care, right? The PCM thinks it's in 2nd all the time so it never uses the P/N settings. The torque management is all disabled. And the A4 trans DTC's have been switched off.

My OS (12208322) never came in a manual, and EFILive won't let me load a different OS to do the segment swap.

Is there more to a "segment" than the settings visible in the tune tool?

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Thats exactly why you want to do a seg swap, if you run a manual segment the T56 should report to the PCM what gear you're in. A big thing is the P/N idle settings including the coastdown tables, I dont believe any of these will ever become active if you dont report to the PCM that its really a manual now and what the clutch status is. The PCM *shouldnt* care either way, just is better to have the PCM know whats going on if you can.

Do you have a V1 Personal or Commercial? Hopefully its a Commercial V1, you can full flash and run a 2002 OS 12212156 for your Silverado then easily do a seg swap to a manual trans. You cannot load different OSs in the V7.5 Tune tool, V8 will have this capability. But you MUST use the same OS to seg swap and I believe this will stay the same in V8.

I didn't know the PCM has the ability to know what gear it's in with a manual. How would it do this, compare VSS to engine speed? There is a place two enter the trans gear ratios in the general transmission parameters, but it only has gears 1-4, and the T56 tune has 4L60E gear ratios in it. My clutch switch is not wired into the PCM either.

V1 Commercial here. I guess I could use the 12212156 OS and swap in a T56 seg from an f-body, but not sure if there is a point if the clutch switch isn't wired to the PCM.

What do you mean by "coastdown tables"?

Thanks for the help, much appreciated!

You have to hook the clutch switch to the PCM and I believe something else as well, sorry manual swaps arent my forte.

Idle coastdown tables, might be the throttle cracker/follower in the LS1 PCM.

There is also the reverse lock out solenoid that does not function correctly if you use an auto calibration in a manual trans. Also a manual is always using the "in gear" airflow tables where an auto will transition between the two.
As Erik has stated, I would find a compatible manual calibration & start from there.

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Originally Posted by 5.7ute

There is also the reverse lock out solenoid that does not function correctly if you use an auto calibration in a manual trans. Also a manual is always using the "in gear" airflow tables where an auto will transition between the two.
As Erik has stated, I would find a compatible manual calibration & start from there.

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Reverse lockout is wired into the brake switch, works perfectly. If the manual tune only uses the in gear tables I don't see what the big issue is using an auto tune that is also fixed to the in gear tables. Unless the PCM indeed knows what gear its in in a manual tune.

With a manual trans segment, the PCM does know what gear the M6 is in (it compares engine RPM to trans VSS while the clutch is engaged)...

look closely at these tables: B5803,4,5,12 (the shift light is a manual trans function).


Also, B3809-12 are DFCO parameters specifically for manual trans equipped engine.


Some of the P/N and IG (in gear) tables apply to manual trans (P/N corresponds to clutch disengaged, IG corresponds to clutch engaged).

Ok guys I have the same problem with my car. I have already done the segment swap as discussed. I also have a clutch switch wired in. My car runs @ 1000 stopped,yet as soon as im over 5mph it jumps to 2000 rpm. go below and it lowers.
I don't know what table is acting on this but it is definately rpm related. You should know I am also running a 98 mm t-body on a ls3 w/ a 02 operating system.any help would be appreciated.