Erratic Idle Lope Issue

[BrodyO]

Hello, I've got a 2005 Chevy Colorado with an Ly6 and 4l80e swapped into it. Running SEP1000cc injectors, 7875 turbocharger, summit stage 3 turbo cam and controlling it with a stock e67 ecu. I've had this issue with the truck since I was naturally aspirated and it's time to get it fixed. Looking for some advice on what to chase.

So, the issue is that when the truck is sitting idling in park it will all of a sudden start loping hard and basically cannot catch itself and bring it back to normal without my input. You will notice in the data log it sits and idles normally for quite a while, then goes unstable. I give it the slightest amount of throttle and it's able to catch itself and go back to desired but it doesn't take long for it to happen again. The idle will bounce from 270 to 1900rpm when the desired is 950.

In the calibration I took a mixture of advice from Goat Rope and HPAcademy on what to change when a larger cam is put into these engines. I have a desired idle speed of about 950 across the board, I increased the stock effective area percent max, I increased the airflow final minimum by around 25% and I cut my idle adaptive spark control by about half.

You will notice in the log that it does manage to catch some smaller erratic areas earlier in the log but it can't on these big ones. I have been looking for what triggers these events (temp based multiplier, etc) but I haven't found one yet.

My thoughts to start would to further increase the stock effective area percent max (HP claimed it might take up to 50% over stock), further reduce the idle adaptive spark control, give it more throttle authority at idle (not sure how to do that) or best yet, have one of you smart folks tell me exactly what to check and modify

Let me know what else you need from me and thanks in advance!

Colorado_7875_VVE Driving_21st_2barVVE_smoothed_BluecatTransmissionTool 07302023.hpt

Colorado_FlexFuel_Ly6_7875_e67_ErraticIdle.hpl

[ns158sl]

I figured it was something EVAP related but doesnt seem so. I guess someone else might have a better idea to look into. I would maybe address the codes though especially the po340. Also is there a reason you are tuning in OL?

[blindsquirrel]

Idle timing is too high - if idle dips, and timing is already so high that adding more doesn't catch it, the only tool it has left is to open the throttle. Throttle is still in the act of opening by the time RPM is back up at the target, but throttle is still opening because it's slooooow, which makes it overshoot, which closes the throttle but too much so it then undershoots and repeats over and over. Feedback loop.

[BrodyO]

Thanks for the reply, that makes sense to me. How big of a change would you recommend? If I'm desiring 25 degrees now, would 22 be a good step? Or should I go more aggressive than that?

[edcmat-l1]

It's pig rich because the injectors are junk. You have no injector control at low pulse widths. It's choking on fuel.

Your timing tables aren't setup right. What you've done in the high octane table, 22 degrees @ idle, that caps the amount of timing the overspeed table can add. You've also limited your under/over tables too much that makes it resort to using the blade which just exacerbates the situation.

First thing is you need to figure out how to get the thing to stoich at idle. I'd throw the injectors in the trash where they belong and put some decent injectors in it.

I'd also recommend putting it back in closed loop and letting the trims dial in the A/F at part throttle.

You said in your post it's a 2005 Colorado. Tune file says it's a 2009.

[edcmat-l1]

timing table.jpg

The area around idle where you have it all 22, you need to put back to stock. Needs to be 30 or even higher in this area.

timing table 2.jpg

Then set your idle timing table around 18. Then put your over/under tables back to stock.

Then put it back in closed loop and dial in your VVE using your trims.

[Alvin]

If that wideband is accurate.. That is the first problem. No sense in trying to work on idle before the airflow models are correct. Whatever you do to make the idle better will need to be undone when the fueling is correct.

Else like others said. Base your idle timing around something like 18 degrees that way you can shoot up in advance to save a idle dip.

[BrodyO]

Agreed with you guys the lambda is out of whack there. I have had a hell of a time dialing in the VVE with this rig, seems if I make an idle change it'll change me everywhere. I'm aware of the zone, blending etc. Not sure if it's me or the injectors. The tune up in there now at least has me in the safe zone at WOT and the last place this truck ran was the track. I need to get my factory 02 bungs welded into this exhaust so I can have it trim but I've been trying to get to a happy place with my VVE first. I will say, even when lean at idle, it will go into this lope, so I don't think that's the MAIN issue.

Great advice here. I will adjust timing as mentioned and report back.

[edcmat-l1]

Post a data log of it idling at stoich.

Also, the VVE is a nightmare. It's nowhere near correct LOOKING never mind numerically correct.

VVE.jpg

Need to ditch the injectors now. Don't put any more time into trying to make them operate correctly.

[BrodyO]

Post a data log of it idling at stoich.

Also, the VVE is a nightmare. It's nowhere near correct LOOKING never mind numerically correct.

VVE.jpg

Need to ditch the injectors now. Don't put any more time into trying to make them operate correctly.

Yeah super chunk, bad transitions, agreed.

I was thinking of going with SEP's "pro series" injectors as they will grant you a credit towards them if you turn in your previous injectors. Their pro series are a genuine Bosch injector with lots of buzz words about them. Anyone have an opinion on them? Planning to go with the same size.

[edcmat-l1]

I won't tune SEPs.

No one who builds anything runs SEPs.

No one who makes any power runs SEPs.

[gtstorey]

I won't tune SEPs.

No one who builds anything runs SEPs.

No one who makes any power runs SEPs.

But tell us what you really think about SEP.

[BrodyO]

Seems to be much more dialed in now. Thanks for the tips!! I just adjusted the timing parameters per the advice.

Colorado_FlexFuel_Ly6_7875_e67_ErraticIdle_ChangesRev1.hpl

[edcmat-l1]

It's still pig rich. Fatter than my next door neighbor's wife.