In gear idle issues!!!

[Webbs]

I have a 99' Silverado with a 6.0,cam,headers, exhaust. My VE and MAF tables are dialed in and my idle in park/neutral is excellent. Now the "but" when I shift into Reverse or drive the truck idles fine for a moment the iac starts to ramp open all the way and the timing drops to 3*. For the life of me I cannot seem to find the culprit!!


Someone take me to school please!!

Perf_0002.tunCrazy truck.efi

[Webbs]

No takers??

[Evolution]

Why aren't you using a COS?

[Webbs]

Why aren't you using a COS?

Did'nt see the need to run a COS. The truck is only a 6.0 with a cam and bolt-ons. No boost, No N20, the truck only makes 370rwhp, not sure why a COS would be necessary?

W~

[joecar]

Looks like PCM is trying to control engine idle speed via IAC and it does not respond so then it tries manipulating timing and it responds incorrectly...

I'm not sure exactly why this is happening...

but have a look thru here:

Idle Tuning
showthread.php?4661-Idle-Tuning-Helpful-Info-Inside
showthread.php?14439-Idle-Tips-amp-Tricks
showthread.php?5866-Auto-VE-questions
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
Stumble-3-seconds-after-cold-start&p=178921#post178921

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

[Webbs]

Looks like PCM is trying to control engine idle speed via IAC and it does not respond so then it tries manipulating timing and it responds incorrectly...

I'm not sure exactly why this is happening...

but have a look thru here:

Joecar,

Thanks for the links. My main issue is that there is nothing in my tune that would allow timing to be pulled. I have gone through and pulled out all of the adders/multiplyers and locked all of my timing tables at 20*. Just to see and it still does the same thing. I must have a wiring or input issue that is causing this?

W~

[maudyZ28]

Joecar,

Thanks for the links. My main issue is that there is nothing in my tune that would allow timing to be pulled. I have gone through and pulled out all of the adders/multiplyers and locked all of my timing tables at 20*. Just to see and it still does the same thing. I must have a wiring or input issue that is causing this?

W~

let me look at the tune over the weekend. I found mine being a nightmare to tune a 228/228 cam with LS6 heads on my LS1 with a stock stall. Needed to keep all learning tables nearly dissabled to allow you to specify the air required and the whicle to not change anything.

[c.u]

What size cam? How much stall.

[maudyZ28]

yeah all looks good at idle and tables all look fine, so the dying only happens when switching into drive? Mine used to do this but spark didnt drop. I'll look into the tune a bit more and compare with mine. Just wanted to let you know I am looking

[maudyZ28]

ok, so your car wants way more air when you shift to gear so start by making desired air flow much more. Something like 13-14. Mine runs at about 13 as is now with cam and stall, and was up in the 18s when I had the stock stall.

The engine is bogging down too much. You also have a stall saver to come in at 700 rpm, I dont know what this does internally. Zero it out as this may be pulling timing behind the scenes?

Also the IAC learning is quite high, I reduced mine to learning much slower so I could dial the correct desired air flow in. This might help but at moment just increase desired air flow and remove stall saver. Dont make too many changes at once.

Check the spark correction based on over and under rpm too. Maybe that when truck starts to stall it tells it to pull more and more timing as RPMs decrease so you fight a loosing battle.

I cannot find anything to say why it is pulling more than 10 degrees out, other than the CAT heat up light off thingy. This says it pulls 10 deg of timing at start up, but this shouldnt still be in effect and truck is fine at idle out of gear!