Gen4 idle tuning guide

[dhoagland]

I know I'm chiming in on this old but very relevant thread, I am running a L92 in a yukon denali xl, just rebuilt the engine with a stage one vvt cam, 58lb injectors, and a cai and headers. I have tried a lot to get it to idle well and it just isnt working the way it should, currently i have a shake and sometimes it bogs down when leaving from a stop. i tried the steps here and it just reved up to around 2000rpm and stayed there (im guessing i messed up a step), so i used some of the settings from all the way back when the thread was created and it idled amazing minus when i blipped the throttle the rpms would drop way below idle level and the engine would stall. I read what to do to correct that and it didnt seem to make any difference. Im at a loss here plus other problems im having with tuning this thing, any advice would be greatly appreciated

At a minimum Post your Tune and log files operating in your areas you are struggling with.
Might be best to start your own thread

[brettstoner]

This guide was very helpful. A couple things I noticed. After getting fueling right, idle speed (750 idle rpm), and timing (20 degrees at idle); I zeroed out my base running airflow table and logged the dynamic airflow for each idle rpm in park and in gear. I then pasted 80% of the value into the table and smoothed it out down and up RPM. I then turned my idle adaptive back on and used the spark correction to dial in the table. I noticed as I got the base idle airflow table dialed in the adaptive spark corrected less and less. Once it was down to 1 degree or less correction I was happy.

I have a BTR Stage 2 LS3 cam that has some chop. With factory spark and air idle corrections I was getting rpm swings back and forth. Controls were too tight. I cut the idle spark correction settings in half, airflow corrections aboout 70% of original, kicked up proportional corrections to 75 rpm, and it idles much smoother. The car stopped correcting for the cam lope and allows it to lope naturally now. Some people like the chop chop chop sound and may want to purposely let a tight idle correction swing back and forth to get that cam sound. I admit. It sounds good. But I am trying to hide the cam and be a sleeper so I muted the adjustment. I could have also dropped the idle speed down to 700 or 725 to get more chop sound.

One other issue I had is coming to a stop the idle would dip too low. The trans was pulling timing for the 2-1 downshift just as I was coming to a stop causing the engine to fall on its face. I left the CT downshift on and raised the 2-1 downshift to 8 mph which elminated it.

Between my remote tune which was fantastic for power and me dialing in my idle the car is a dream to drive now. It really helped to make a change, log the idle (letting my changes settle out and injector tip temp to come back down after reflash), and see how my adjustments changed how the car adapts/changes the idle.

[Triple P]

Is there a trick to getting the RPM error graph to populate? Nothing shows up on my graph or chart. I'm using the files bigmike42 posted early on.

[SFM]

I got the car to Idle perfectly and found the best smoothest Idle to be around 9.5 g/s around 22 and 24 degrees of spark. however it just won't drop to my target Idle, I have tried targeting idle on 800 but the actual reading is 1,000 ~1,150 rpms I have even tried raising/lowering Min airflow & spark tables but no matter what I try the Rpm won't drop below 1000 rpms.only way I could drop it is by raising the ETC AREA SCALAR, now keep in mind that with the stock setting it wouldn't drop RPM below 1,500 rpm for some reason.

The car was previously tuned by 2 tuners while power was great, Idling and drivability were crappy.

6.9L stroked LS3
10.5:1 CR
ported heads
BTR Stage 3 NA Camshaft Specs: 239/254 .631"/.610" 114+3
6.2L denali Intake Manifold
90mm Silverblade TB
2010 Camaro Injectors


engine is swapped FYI

I attached a log of the latest tune, I know there is much to do in the tune but I am taking it in small steps.

Starts up fine, No issues and did around a bit of maf tuning (Car still runs open loop MAF only in attached tune) once I dial in this Idle issue and make sure its no longer surgin on Idle/Roundabout/AC on then I will finish up the MAF and move over to VE tuning.

Would Appreciate any suggestions instead of me messing with the ETC Scalar and any tips to get this done.

Thanks.

[marksrig]

Seems something is amiss with my step 1 file. I set what I knew from Mikes first post, but I still have to lightly pedal the engine to keep it going. It doesn't seem to matter what I put in the base airflow.
What did I miss? It sounded so simple.

step 1 IDLE CONTROL.hpt

[marksrig]

This is the best it will do. doesnt seem to matter how much spark or airlow minimum, it barely idles.

idle test.hpl


It seems that Throttle is always at 7.1% and it wants to die

EDIT:
07GTS's post #160 seems to help tremendously. Proportional airflows back to original and not zeroed out fixed the issue. Now I can tune. I guess I misunderstood what needed zeroed or it doesnt work with the E67.

"your base running airflow v ECT mult is zeroed out try that back to stock, and ALL your "follower torque" is zero too that wont help at all go back to stock, and all your adaptive airflow corrections are zeroed out that means that the ect isnt going to help at all, to dial in idle airflow put all those airflow tables back to stock and then zero out the spark correction tables and set idle spark tables to all the same say 16 then main spark to all 16 also so idle spark stays steady, then see what its like and adjust the airflow tables to dial it in and then once its good use spark as the last help (spark correction should be minimal if airflow is setup correct) also with those spark correction numbers maby try halving them"

[LukeyB]

Just did this today. I can usually get close just stumbling through but i was having a shudder (lots of misfires) Whenever I had a timing dip. Set my timing locked to 20*, was able to knock 50 rpm out of my idle speeds and dialed it in in about an hour. Used the CTSV airflow numbers. Misfires changed to 1-4 here and there which is just the larger cam im sure. So i desensitized that and it runs beautifully.

[Roncomp]

Just found this thread today. I changed my tune with the changes you listed, and bingo all is well. GMC 2012, 5.3 w/btr Truck Norris cam and springs, 6l80-tuned. The transmission still has a slam shift 6-3 and 6-2 I think!

[Allen Vos]

This is the best it will do. doesnt seem to matter how much spark or airlow minimum, it barely idles.

idle test.hpl


It seems that Throttle is always at 7.1% and it wants to die

EDIT:
07GTS's post #160 seems to help tremendously. Proportional airflows back to original and not zeroed out fixed the issue. Now I can tune. I guess I misunderstood what needed zeroed or it doesnt work with the E67.

"your base running airflow v ECT mult is zeroed out try that back to stock, and ALL your "follower torque" is zero too that wont help at all go back to stock, and all your adaptive airflow corrections are zeroed out that means that the ect isnt going to help at all, to dial in idle airflow put all those airflow tables back to stock and then zero out the spark correction tables and set idle spark tables to all the same say 16 then main spark to all 16 also so idle spark stays steady, then see what its like and adjust the airflow tables to dial it in and then once its good use spark as the last help (spark correction should be minimal if airflow is setup correct) also with those spark correction numbers maby try halving them"

I know this is an old thread, but the idea of zeroing everything out is so that there is nothing controlling the throttle blade or ignition timing during idle "while" your are trying to find the min idle setting in this procedure.

That's why it wants to die. I found with mine, if you just lightly pedal the throttle for 20-30 seconds it would stay running unless your min air settings are to low.

You need to pay attention to the RPM error and that is your indicator for min air flow.

One thing I found is the min air flow is not to far off what the MAF sensor reads at an engine idle when hot.

Once you have figured out min air, then put all the tables back the way you had them before or stock as 07GTS said.

[FC3S Murray]

MAF data does reflect a pretty accurate idle minimum airflow at operating temp. Seen this multiple times.

[nathanhine1977]

Hi guys, I have spent countless hours trying to nail down a good, concrete method for tuning gen4 vehicles. Today I finally came up with a consistent method to dial in base airflow that I haven't seen posted before, so I wanted to share it with the community. This guide is for airflow and the adaptives only, so I am going to assume fueling is already dialed in if you decide to try my methods.

Before I dive into the steps, I want to briefly go over how the idle works on the gen4 pcm. There are 5 main areas that control idle: Airflow final minimum, base idle spark, spark over/under speed, proportional airflow, and integral airflow. These tables work closely together to attempt to keep your idle error to a minimum. Airflow final minimum is just your base air before any corrections. Base idle spark is self explanatory, as is over/under spark. Proportional airflow is an instant airflow correction based on real time rpm error. Integral is an offset airflow correction that gets applied to your airflow final minimum based on error over time. Proportional is to STFT as integral is to LTFT. It is your run of the mill PI controller, except it has different factors depending on how severe the RPM error is (the higher error, the more correction, and vice versa).

The problem is, the adaptives are way over tuned from the factory, so as soon as you put an aftermarket cam in that oscillates significantly more than the factory cam, you end up with a very over reactive idle. You get spark going one direction, over correcting, then airflow correcting back the other direction since it is a much slower correction than spark. It is a vicious cycle as spark correction competes directly against airflow correction.

The problem with just setting base airflow and calling it a day is you are tuning against two moving targets, the airflow correction and the spark correction. It's akin to trying to tune your maf table while the ve table is still enabled.

What you really want to be do is turn off the adaptives completely, lock in your spark, and find your optimal base running airflow. Base running airflow is nothing more than base TPS %. So how do we do this?

Is this method still the best way to dial in Idle ?

[schpenxel]

I've used this method a few times and it has worked well for me. At the very least, I understood the idle strategy of these ECM's much better after going through it.

Though to be fair, I haven't had a ton of trouble getting gen 4's to idle for whatever reason. I'll take them over an old school IAC/gen 3 all day every day

[Cringer]

Is this method still the best way to dial in Idle ?

The Gen4 ECM has throttle adaptives (Proportional and Integral) for airflow. These controls add or remove air flow to the engine to maintain the desired idle speed (along with the timing). The first thing this guide does to attempt to tune idle by defining (aka excessively raising) the Minimum Final Airflow -- resulting in killing half of your airflow adaptives! By setting the MINIMUM, the P/I controller is handicapped because it is not able to remove as much air as it may want to in an overspeed situation....so the ECM is then forced to compensate by removing a bunch of timing to reduce idle RPMs. Depending on your overspeed timing and minimum final spark tables, you may not have enough leeway to pull timing and the idle will hang of be lazy to return or even drive itself in a worse case scenario.

If your virtual torque is higher than the limits defined in the BTL table, that can even cause idle issues.

The bottom line is, at least my personal opinion, you should not tune idle by jacking with the adaptives or the min final air table. So I would not rely on this guide personally. It would be best to post your tune and log and let the community help (and ask your specific questions/problems along with it).

[smokeshow]

The Gen4 ECM has throttle adaptives (Proportional and Integral) for airflow. These controls add or remove air flow to the engine to maintain the desired idle speed (along with the timing). The first thing this guide does to attempt to tune idle by defining (aka excessively raising) the Minimum Final Airflow -- resulting in killing half of your airflow adaptives! By setting the MINIMUM, the P/I controller is handicapped because it is not able to remove as much air as it may want to in an overspeed situation....so the ECM is then forced to compensate by removing a bunch of timing to reduce idle RPMs. Depending on your overspeed timing and minimum final spark tables, you may not have enough leeway to pull timing and the idle will hang of be lazy to return or even drive itself in a worse case scenario.

If your virtual torque is higher than the limits defined in the BTL table, that can even cause idle issues.

The bottom line is, at least my personal opinion, you should not tune idle by jacking with the adaptives or the min final air table. So I would not rely on this guide personally. It would be best to post your tune and log and let the community help (and ask your specific questions/problems along with it).

I call those trampoline toons.

[jlquick]

Hey guys. I am trying to follow this guide for idle and not having much success. After revving up engine as instructed, the idle goes up, and never comes back down. I've set the timing to 18* across the board and then tried 15*. I've cut the base final airflow table by 20%, then an additional 15%, and it still stays at 1,500-1,800RPM even though idle target is 750.

Any suggestions? I would greatly appreciate the help.

3.hpl
07 TBSS 6-16-25 trans reset idle tuning 2.hpt
4.hpl

[cessnageek]

What are the mods? Like Cringer posted above, this isn't necessarily the best guide to follow.

It looks like you've tried to fail MAF, but didn't set P0101, P0102, and P0103 to MIL on first error. I'd start there. Right now the MAF is reporting 12 g/s across the board, which drags your dynamic air down even though you are at 30% throttle at 1800 rpm.

[jlquick]

It's an E67 PCM running 08 Saab 9-7X Aero OS that is compatible with a T43 TCM in a 6L80E.

The engine is an LS3, with a Magnuson 2650 Supercharger, ID1300s, BTR Positive Displacement Cam Stage 2.
Transmission is a new GMPP 6L80E, with a billet triple disc 2600 stall converter.

[cessnageek]

That combo is well outside anything I have experience with, so I'm not going to offer advice there. However, my previous point is still correct. You need to fail the MAF properly if you haven't already done so. The CEL should be on if you do it right.