off throttle dying after tranny swap...

[Superado]

when stopping at a light or such...rpms drop below idle and cuts off
when slowing down and off throttle to make a turn...rpms drop below idle and cuts off...
had this issue after new motor, but finally got it to stop w/ alot of idle tune suggestions I read here...
then broke 4L60e again and replaced w/ 4L80e and slightly higher stall...
and it's doing this again...appears to peg lean each time this happens...
any ideas?

[Superado]

also...if I catch it before it cuts off and give it a little gas...it richens back up, rpms rise back to set idle and will sit and idle as long as I want...???

[joecar]

Sounds like a engine tune problem... (I'll delete the duplicate posts).

[joecar]

Did you check that all the grounds are still ok and that no wires got pinched between motor and trans...?

Did you check that the vacuum lines are all still ok and attached...?

[Superado]

yep...
only does it in-gear while slowing down to a stop or right after stopping...

[jfpilla]

With a higher stall converter you have less engine braking. That causes faster decrease of RPMs and often overshooting of the targeted RPMs.
As a test, increase your RPMs. If that helps then it's likely you need to redo the throttle cracker.
I found it a lot easier to turn on the TC at 24mph and off at 23mph raise the RPMs by 50. Lazy maybe but it works great with not a hint of surge or hunting.

[Superado]

I'll give that a shot...THANK YOU VERY MUCH!

[joecar]

Makes sense.

[Superado]

changed throttle cracker to 24 on and 23 off...
increased all desired idle rpms by 50...
helped a little, especially on turns...but still dropping below desired rpm...searching, surging, lean, rich, lean...cutting off :confused:
all of this at stops and when making 90° + turns :help2:

[joecar]

Post some logs when you can (I already have your tune file from the other thread).

[Superado]

tune after TC changes...
log @ lunch today...
three cut-offs
one almost cut-off but saved
one no cut-off at a stop

[Superado]

raised rpm on stall saver as suggested in one thread...didn't help
increased spark tables thru 800 rpm as suggested in another thread...didn't help
went back to tune posted above and its worse now than originally :confused:
realized that I wasn't logging WB in above posted log...will have to log again and post tomorrow...

:help2:

[jfpilla]

As joecar suggested. "It sounds like a tuning problem." I would start over from scratch and add ltrims and maffreq to your scans.

[beaukz28]

Make sure that you clear trans adapts after trans work. Sometimes the ecm is trying to compensate for thens issues that do not exist anymore. I have overhauled and replaced many gm tranny's. Mostly 4l60-e on trucks. I get alot of trucks and mostly blazers that once the battery is disconnected for a couple of days the will not idle and stall. It usually takes about a day of driving to clear up. I had a couple of trailblazers that took about two days. Make sure your battery connections are clean and tight. I don't know why it happens or why some do it and others do not but it happens to me about 1 out of 8. My advise before you change things, drive it for a week and see if it relearns.