Uneven Idle

[2K_Silverado]

The patient is a 2000 Silverado, stock LS3 crate (430HP), 90mm Holley Sniper TB (cable), truck intake, Airaid Jr. tube, stock MAF and airbox, Kooks long tubes. Engine has about 600 miles on it now. Trans is a Tremec Magnum.

My problem is an uneven idle. It also dies sometimes after a throttle blip or as I come to a stop. What's worse is that sometimes it will die as I make a left turn. Not a good situation.

The only things I have changed in my tune from the shop's settings is correct the tire size and the fan operation. All other settings are theirs.

Attached is my current tune and a cold start to warmed up log file. I'm new to the tuning world and would appreciate any assistance in getting this idle and stalling thing resolved.

[Pekka_Perkeles]

Your fueling at idle is WAY off... STFT is +50% or so...

[2K_Silverado]

Thanks, Pekka. I should have mentioned that I saw that in the log but was unsure about where to fix it. You know, newbie uncertainty...

If I'm not mistaken, I make the adjustments in the Primary VE and Secondary VE tables, correct? And I should add the percentage that I see in the log to the appropriate cell(s) in those tables? So if I'm off by +50% I should multiply that cell by 1.5. Do I have that right?

[5FDP]

What is your fuel pressure like?

The only time your o2 sensors move off of extremely lean is when you give it a little bit of throttle.

I'd verify fuel pressure, make sure you have zero vacuum leaks or exhaust leak pre-o2 sensor. Then install a wideband and start tuning this thing.

If the trims are still that bad after checking fuel pressure and leaks, hit the MAF curve and VE tables with like 10%. See if the trims drop way down.

[2K_Silverado]

Haven't checked FP yet, but the pump is a brand new Walbro TU432HP-2 which is supposed to give me 58 psi and 230 lph @13.5v. I'll check it today after I buy the tester. I'll also check for vacuum and exhaust leaks while I'm at it.

[2K_Silverado]

RESOLVED!!!

So I found a shop in NC that was able to fix my tune via email. (Shame on the original shop for failing so miserably…) In just a few hours I received their first update. They got the STFTs into the green and by comparing their tune with mine, I could see that they made a bunch of changes in a bunch of places. I would never have been able to do what they did. I sent them a log for review and they sent me another update the next morning. STFTs are better but still not perfect (still some double digit cells.) I sent them another log today and I'm waiting for the next update.

So while I'm waiting for that, I wanted to look into my high idle at warm start and "auto cruise control" problem. A search of the web provided me with the solution from another forum. It may be bad form to post the link here, so Google "IAC Position vs. Effective Area Table revealed in HPTuners" and you'll find it. I followed those instructions and now the truck starts easy and settles into a nice rhythm quickly. Idle is still higher than the requested 700, but it doesn't race at startup like it did and there's no high idle coming to a stop in neutral.

So for the higher than desired idle problem, I removed a total of 9 degrees of timing from the 0, 400 and 800 columns in the In Drive and In Park tables that you find in Engine/Spark/Advance. Idle was in the upper 790 - 830 range. Now it's about 740 - 750ish. Much better, but still not perfect. More to do there. Or maybe that's not the place to do it. Perhaps I need less air instead of less spark. I dunno.

I just got back from a test drive and everything is running really well. Once I get the next tune update I hope that the STFTs are in the single digits and I can just go out and drive.

I have to say that going from a tired 4.8/MG5/3.42 to a 6.2/Tremec Magnum/4.56 has put a serious grin on my face. I've learned a lot in this process and I've come to realize that I will never be a tuner. By choice. I'll leave that to the professionals. It'll be a lot easier on my sanity...