Help with open loop (cold start) tuning

[12sec.5.3]

When I crank up the engine in open loop (cold) the idle is really low around 500-600 rpm and will not stay running. After I warm it up it goes to my closed loop setting of 850 rpms and is fine. I went through every file I can think of but I can't find the problem.

[Taz]

Hello 12sec5.3,

Post your current tune ... so other Forum members can help ... another pair of eyes often comes up with a solution.


Regards,
Taz

[12sec.5.3]

I'm a little embarrassed but feel free to help with any other issues you may see..
9495

[Taz]

The tune is far from stock - any modifications to the engine ?? It's a 5.3 L, not a 6.0 L correct ?

Need to know before making / suggesting changes.


Regards,
Taz

[12sec.5.3]

370 cu., l92 heads ported, custom grind comp cam, l76 intake, 42 lb inj., 3600 circle D

[12sec.5.3]

:doh2: and boltons :hihi:

[WeathermanShawn]

I'm surprised that your Table B4343 values did not do the trick for you.

You could always try adding 2-3 g/s in this Table. It almost always works. Granted when it starts it may sound like a jet engine if you overload it with too much air..but that Table usually solves the problem..

[12sec.5.3]

I don't know if that table is the cause, but sometimes it idles around 1500rpms for no reason that I can think of. Go drive around a nail it a bit and it stops. idk wt the hell...

[Taz]

WOW !!! That’s a lot of mixing and matching ! WeathermanShawn is our resident idle expert, so you’re in good hands.

Took a quick look, you have the idle learn parameters disabled - B4322 through B4328, I try to leave these active to allow the PCM to assist with changing conditions.

The L76 intake – Holden product or GM truck ? Believe they may have a different volume.

What throttle body are you using with the L76 intake ?

What MAP sensor are you using ?


Cheers,
Taz

[12sec.5.3]

Stock MAP. Holden intake. 90mm ComTech

[WeathermanShawn]

Normally with Idle problems I have learned that the farther your Tune is away from stock..the more time and effort you will spend trying to track the problem down. These Tables will build upon one another and you will end up spending days or weeks trying to figure it out...I know that is not always possible when your intake/TB are not stock.

That being said, I totally agree with TAZ that you have inadvertently disabled the Learning Parameters. The only other issue would be your Desired Airflow. Any way to smooth out those values? You can check out a little Idle Tutorial that will at least give you a pathway to follow. Check under GEN III stickies.

It definitely sounds like an Airflow problem, or worst case an intake air leak..

[Taz]

Your engine now displaces just a little over 6 L. You are using a tune originally from a 2002 5.3 L. I would recommend copying over the idle / start up parameters from a 2002 6.0 L as a starting point.

If your VE values are reasonably accurate, that should make tuning a little easier. Your B4401 value varies greatly from stock - not sure what IAC you are using.

Would then enable B4322 through B4328 (stock values) and proceed with a PCM Idle Learn Procedure. Hopefully this would afford you a better starting point to begin tuning the idle for your specific components.


Regards,
Taz

[12sec.5.3]

Thanks guys I'll give those things a try.