Supercharged H2 idling too high uless i unplug the neutral saftey after it starts

[bstuder11]

Ok hopefully someone can tell me how to bypass something or how to fix this problem. My H2 wants to idle at about 1100 when I come to a stop which leaves me holding the brake hard. After I sit there for about 30 seconds it will eventually idle down to about 7or8oo. After frying a few pcms by trying to pull all the idle values I could think of down I was able to determine that if i start the truck, put it in neutral and crawl under it and unplug the neutral saftey switch It idled down and ran PERFECT. Problem is you cant just leave it unplugged obvioulsy because it wont start, let you take it out of park, unlock the doors when you put it in park, shift to 4 low lock ect... someone PLEASE tell me what to do!!! Thanks, Studer
ps. yes I have replaced the Neutral Saftey Switch

[joecar]

Studer,

What year/model/vehicle is this...?

[bstuder11]

2004 Hummer H2. 6.0L with a 2300 Magnacharger.

[joecar]

Ok, I thought Hummer... this is the wrong section, I'll move it to GenIII.

[joecar]

You will need some of what's in here:

Idle Tuning
showthread.php?4661-Idle-Tuning-Helpful-Info-Inside
showthread.php?14439-Idle-Tips-amp-Tricks
showthread.php?14153-scan-tool-wont-log-rafig-or-rafpn
showthread.php?14435-Need-help-Can-Start-Car-but-dies-when-I-give-it-any-throttle-before-going-to-CL
showthread.php?7011-ETC-cars-and-IAC-parameters
showthread.php?14544-Working-on-my-idle-tune
showthread.php?14794-Help-with-open-loop-%28cold-start%29-tuning
showthread.php?149-Idle-%28Transition%29-Tuning

More Idle Tuning
showthread.php?t=149
showthread.php?t=5866
showthread.php?p=86553 post #17
showthread.php?t=2630
showthread.php?t=473

Throttle Cracker/Follower
showthread.php?t=3568
showthread.php?t=4081
showthread.php?t=5406
showthread.php?t=5940

[joecar]

It seems to me your IG (in gear) and PN (park/neutral) idle airflow tables need some work, I'm not sure exactly, the answer is in those threads.

[bstuder11]

Yeah, thats what the guy I had doing my tuning thought as well and he trimmed it all down as far as he could and it seemed to help a little bit but then eventually locked up my PCM as well as 3 more before I bought my own V2 and went back to a more stock tune for the idle so now im back to where I was. Its so frustrating because as soon as I unhook the Neutral safety switch It runs and drives PERFECT so i was hoping someone would have ran into this before and know what i needed to do. Thanks for trying to help me though!!

[joecar]

The P/N switch has an input to the PCM, the PCM uses this input to select PN or IG idle tables.

Post your tune file (if that's ok) and some logs, we'll work on it together, hopefully some can guide us...

the PCM should not lock up unless the electronic throttle tables have been incorrectly touched.

[bstuder11]

Ok, thats really cool of you and I appreciate the help. Idk if I'll get it up here tonight though; it's after 11pm here and about to go to bed. The guy who previously tuned my truck has been doing it for many yrs though and he tried all kinds of things from rolling idle to throttle cracker to follower and so on and never could get it to run right until I unplugged the neutral safety and then it runs perfect but needless to say I'm getting tired of rolling under the truck to unhook that and then plug it back in to start it. I wish I could just figure out how to bypass that and it would b all good.

[MECHAN12]

Well you could splice a switch in the line and mount it in the cab for yep use until you figure it out
Donald