PDA

View Full Version : High idle until come to complete stop


bgray
May 29th, 2016, 11:31 AM
Hey everyone

My personal truck is a 99 GMC Sierra that has a built 6.0 and swapped to t56.

The issue im having is the truck likes to idle at 1300-1500 when I'm clutched in and comming to a stop. As soon as I stop it drops down to its desired 850-900rpm set. What makes it annoying is trying to go slowly through parking lots, and not revving making a scene for no reason

What tables and adjustments should I be looking at?

Thanks a lot

Brandon
Ben.
May 29th, 2016, 01:21 PM
Throttle Cracker. Just reduce it a bit at a time in the area's you're having trouble with.
joecar
May 29th, 2016, 02:31 PM
Did you flash in a manual trans tune (or do trans and trans diag segments swap from a manual trans tune file)...?
bgray
June 4th, 2016, 01:04 AM
I honestly dont know the answer to that. I had a pretty reputable tuner do the intial tuning. He tuned the truck prior to me doing the T56 swap, then retuned after the swap. So i would be inclined to say he likely used the old map.
Taz
June 4th, 2016, 01:33 AM
Post your tune - which will help end much of the guess work.

Was the T56 VSS wired to the PCM ?

Was a clutch switch wired to the PCM ?
bgray
June 4th, 2016, 01:41 AM
see attached.

The VSS is wired in, no clutch switched wired to pcm.
bgray
June 4th, 2016, 01:56 AM
I should also add, IF im jsut in neautral and rev the truck it will rev up, dip down to 1900 rpm, then hang there and slowly come down 1900,1800, 1500, 1200 then go to desired idle. What table is that?
Taz
June 4th, 2016, 04:28 AM
OK … that is a COS 5 upgrade of 2002 OS12212156. It looks like the original tune was from an LQ4 6.0L 4L80 truck, and has had 2002 Camaro manual transmission segments swapped into it.

I would recommend beginning with either a 2002 LQ4 manual transmission tune, or a 2002 Camaro LS1 manual transmission tune, and making changes / upgrading to a COS from that point.

The hanging Idle is a common problem when trying to use an automatic transmission based tune, to control a vehicle that has a manual transmission.

You do not absolutely need to wire in a clutch switch, but this addition provides the best drivability - once you have an actual manual transmission tune in place.