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Gen IV E38 PCM Airflow tuning

12K views 20 replies 8 participants last post by  2000_SS 
#1 ·
Was wondering if you guys had any insight on Idle Airflow tuning on a Gen IV LS vehicle equipped with Electronic Throttle. It seems that no matter what changes I make to any of the idle airflow tables or throttle tables I cannot get this vehicle to idle with the A/C on and it wants to die coming to a stop.

The truck has a bone stock 5.3 with 72lb injectors and a 2bar map sensor. It has a 76mm t4 turbo, I believe the KB racing kit. I am using HPtuners with the 2bar custom OS. The VE table is dialed in, drives fine, STFTs are all dialed in, WOT AFR error is dialed in as well. Vehicle is pretty much done aside from the idle airflow stuff. I read a how to "Bills idle tuning" but it still doesn't get me to where I need to be. When you command idle up in the VCM controls anything over 800 or so it will not go up, timing goes up to 30*+ advance to try to keep engine running but it seems the throttle will not crack open anymore like I want it to. This is the first Gen IV I've done and I appreciate any ideas or help. Thank you.
 
#2 ·
ok they are a simple beast, depending on your cam you may need a hole in the TB to make it work correctly, start off at 1/8", you need to keep the idle TPS at close to stock or you will have all sorts of problems,

what is your idle TPS %?
 
#8 ·
I assumed it had a big cam in it... if you have a big cam the best way is to give the engine a small hole to get it to work as when your idle throttle % gets too high it fucks with a lot of things..
 
#7 ·
Turn your idle timing down, then crank in base running airflow to bring idle back up. The lower timing allows the idle timing to function correctly because now when it adds timing, it can actually raise idle from having more torque.

You may need to change the coast down table as well as the main ign map.
 
#11 ·
Turn idle timing down, needs to be in the 6-13* range.

In the idle tab, go to base idle or base running airflow, and multiply the table by 1.5, and see what it does. Might be 25% more, might be twice more. I'm just shooting off the hip.

You can email me a log and the file too, if you want. Louisgigliotti at yahoo.com
 
#17 ·
Ok so ive been pissing with it but still cant get it to idle after 750rpms. The idle AFRs seem to be fine but the issue looks like no matter how much idle airflow i crank into it it a 16-17% ETC opening maximum and so when I try getting it to idle higher it will just add a bunch of timing. Is there a way I can get past this limit?
 
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