Idle issues

[Ben.]

Hey guys, after trying for many hours, I've decided to admit defeat and ask for help. I'll try to give as much info as I can without rambling on too much. Car is a VY Holden Commodore, LS1 ECM, 227/223@115LSA, ID2000's, E85, T56 trans. Capacity I was told was 383ci, however it may still only be 346ci.

makes good power, drives great, cold starts like a champ. There are two main issues I'm having, one is livable, I'll get to that later.

The first, and biggest annoyance is when returning to idle. If I'm cruising and clutch in, revs will drop straight down to 500ish, stumble a bit then swing back up to 1500 and continue swinging between those points. sometimes it will slowly get smaller and smaller, eventually settling at idle, other times it will just get worse and die. I've tried all manner of things thus far, including: Run idle config to obtain my base running airflow (Did this twice to make sure), made adjustments to my PID settings, Idle spark under and over speed, moved base VE up and down, moved timing up and down and plenty of other stuff that I can't quite remember at the moment. The only way I can get it half way reasonable is to activate the LTIT (I've been leaving it off to try and get my idle right first) and setting my base running airflow a full two numbers higher than it should be, so that it catches the idle high, around 1200rpm, then slowly pulls it back down to 900. I don't mind a bandaid fix just to make it drivable as it's my own car, but this feels like I'm using the bandaid to patch a bullet wound.

Two things with this, after reading plenty of other idle issue threads, one common thing I found was the 'Final Idle Airflow Minimum', however I can't find this in my HP tuners, is this only for gen 4 cars? The other thing is the DFCO, I've heard of this effecting other cars in similar ways, however looking at my file, unless I've missed something, I don't think it should, but if someone could spare the time to look at it I'd be very appreciative.

The second issue, which I feel might be contributing to the first, is a constant oscillation at low RPM. I go into VCM scanner, fix the IAC at 110 steps, which results in around 1200rpm, and I can get it nice and steady, bring the IAC steps down to around 1000rpm, and it picks up an oscilation, just a steady up and down movement, a total swing of about 100-200rpm, slow and steady. This is with Idle Spark disabled. I can make small adjustments to get it right, but then when I bring it down to 900RPM (about 40 steps, where I want it to idle), it will start swinging again, I can't get it steady across all those points. So, in short, with o2 feedback off, I set IAC steps to make sure the IAC isnt swinging around, turn off idle spark for the same reason, just back to basics, using the fuel and spark maps to get it right, but it's almost impossible. I don't think I should need to resort to changing the rpm scale to ad in more break points with such a 'mild' combo, however I can if need be.

Appologies for not providing a log of the problem, I live with a couple of people that work night shift and an open piped, cammed LS isn't their choice of alarm clock (now there's a million dollar idea!). So if any of you guys have any advice, I'd be all ears. Don't need to go through and edit my tune, even any general words of advice, I'm happy to do the rest myself. I haven't verified timing or A:F ratio, however while messing with the idle, I have got it to pretty much the 'sweet spot' for max vacuum and idle quality where it is, so it's got to be close.

cheers,
Ben
(so much for not rambling on, hey?)
idle problem.hpt

[SultanHassanMasTuning]

your running E85 fuel but your stoich is for gasonline?

[Ben.]

Yes, I did note that. The car was originally tuned by a guy here in Australia, who is probably one of the best known for building big hp stuff, 2000rwhp+ stuff, and is link to think he wouldn't have missed something so basic. I myself have done a reasonable amount of tuning, but this is my first crack with hp tuners, I'm still coming to terms with the logic behind the oem computer versus a typical aftermarket type.

I had drawn the conclusion that the o2'same ate reading lambda, and making adjustments based on this, and that value is just used to determine the numbers being displayed on the screen. Or am I misinterpreting how the system works? Does it used that combined with injector data to calculate injector pulse widths?

Appreciate the input.

[C5 2000]

Compare your file with stock tune and check Throttle Follower tables, like Airflow Mult vs.RPM.

[Ben.]

I actually for my hands on a stock tune for my car last night and did just that. I had previously been looking at stock tunes for 5.3's, 4.8's etc. Copied them all over and just waiting to try it.

If anyone has a point of comparison, could they kindly check that my injector data is correct, particularly the voltage offset table. It looks a bit odd to me, but then so do a lot of tables in hptuners.

As for the VE table, is it likely necessary that I would need to change the rpm scale around idle areas to get enough resolution for a smooth idle with this cam?

Thanks again.

[Ben.]

Upon further reading in this thread: http://www.hptuners.com/forum/showth...2-5-no-working

It seems that I may need to set my voltage offset table to one number? My offset table now is far from that. He also mentions that the Stoich value does need to be set for E85. Can anyone confirm or deny that this is the case with the older LS1 PCM as opposed to the later gen 4 computer mentioned in the thread above?