Camaro V6 / manual M6 bogging/jerking while releasing clutch pedal

[paul_z28]

Hi,

2016 Camaro V6 3.6L LGX w/manual M6 transmission, E82 ECU, car is all stock right now. I've been trying to use HPT to resolve an old problem I've had since the car was new.

Basically as I'm releasing the clutch, the RPMs seem to shoot up and down once or twice until the clutch is mostly released, and then things settle down and it drives normally.

The effect is that when doing a moderate, normal takeoff from a start, or shifting 1st->2nd, the car lags or bucks and won't engage the clutch smoothly because the RPMs are oscillating up and down while I'm releasing the clutch pedal.

I've read dozens of forum posts about issues that sound similar to this. I've already tried adjusting or disabling the following settings, which didn't help:

- Idle -> "Launch assist"
- M6 spark smoothing
- Fuel -> Cutoff settings like CFCO, Manual Gear Type, Use Predicted Torque, Switchover Delay, NLS, Commanded Torque limits

It feels like one or two things is going on:

- When I get the clutch pedal released maybe 30%, some kind of 'launch helper' algorithm kicks in and increases the engine demand; then, as I let out the clutch pedal past maybe 70-80%, the extra engine demand goes away and the throttle pedal responds normally again.

- And/or, when the extra engine demand kicks in, it hits some kind of limiter and the ECU cuts spark and throttle temporarily until the RPMs reduce, then the throttle and spark go back up again.

Here are some of the many threads I've already been through, but the solutions given didn't seem to help in my case:

https://forum.hptuners.com/showthrea...ts-6spd/page2&

https://forum.hptuners.com/showthrea...t-issues/page2

https://forum.hptuners.com/showthrea...-Launch/page2&

The attached log shows a demonstration -- look near the end starting at 16:02:48, where I go through 6-7 cycles of this. I'm doing a gentle takeoff from a stop, and you can see the Absolute Load shoot up way past 100%, then it cuts timing and throttle even though I'm holding the throttle pedal steady the whole time.

What I'm looking for:

- Is there a table where I can shut off the extra 'throttle assist' or whatever, that kicks in when I'm releasing the clutch? I've driven a stick all my life and don't need or want any extra 'help' from the ECU!

- Are there any other tables that could be added to HPT for this ECU, that would let me fix this?

- Can the ECU OS be upgraded or fixed not to do this 'assist'?

I know this is not a common ECU or engine platform, but if someone can help me fix this it would make a huge difference in drivability on this car and for anyone else suffering with this problem.

Attached is my stock tune, current tune and log file. Let me know if I can provide any other logs or info.

Thanks!!

-Paul


Log from current tune: scan1_09102023.hpl
Layout for the log: scan1.Layout.xml
Stock tune: stock_06092022.hpt
Current tune: read_09102023.hpt

[blindsquirrel]

If it did this with the tune 100% stock, I'd say that it's not a tune issue, or even something you should be looking to 'fix' with the tune. It's a real pity that there's no MAF, or cylair, or injector PWs, or delivered torque, or the other many many torque limiting source channels, or O2 data, in your log. Because the times I have seen this behavior before was from something like a bad motor mount that allows the engine to move too much, which over time has cracked the air intake tube, and when the engine moves and opens up the split in the tube the MAF signal drops out and the engine bogs. When the tube closes back up MAF returns and the engine picks back up, rinse, repeat. The ones I have seen do this can be pretty violent about it.

[paul_z28]

Hi, thanks for taking a look & replying... as far as I know there's no physical damage to the motor; once the clutch pedal is released, it drives fine, accelerates, decelerates with no hesitation or loss of power at any time... the problem only happens as I'm releasing the clutch pedal.

I can add those other pids in that you mentioned, but here are a couple older logs I took which might include some of the torque numbers you mentioned -- in the test5.hpl one at 12:44:05 for example, you can see the Abs. Load get up to 150% and Driver Pedal/Final Axle Torque Request are 3000-4000 lb-ft, which doesn't seem right... and I can't figure out any explanation for that.

Looking at VCM Scanner, I see Delivered Engine Torque which I can add, but I don't know what other torque limiting source channels I should look for; do you have examples of those?

I've seen mention of things like that and other tables that seem to exist for the V8s but I don't see them on my ECU or maybe HPT just doesn't show them... or maybe I'm just not looking in the right place...

Thanks again...

test4.hpl
test5.hpl

[blindsquirrel]

So if it's all stock and it does this with a stock tune, do you think every other Camaro of the same year/engine does this same thing? Or do you think maybe there's some non-tune problem you haven't been able to find yet?

[blindsquirrel]

Trying to find a delicate way to ask this, and failing, so: Does it do this no matter who is driving the car?

[CYN_CRVR]

Your description of your problem sounds different to me than the threads you linked.

I agree that if your engine and tune is stock, then a hardware issue seems the most likely culprit for your problem.

If you care to compare to look for any differences, I've attached the stock tune from my 2023 manual V6 Camaro.

[paul_z28]

Hi, thanks for sending your tune, I appreciate it... nothing jumps out at me but I'll look at it in some more detail.

Yeah, I've been wondering why more people aren't asking about this too... at first (since this was my first drive-by-wire car) I thought it was just a normal quirk of a DBW setup... later, I started finding posts about 'bog on launch' and 'throttle lag' and that sort of thing, and started wondering if a tune could cure it. I tried a 3rd-party 'canned' tune and it made the car seem faster, but didn't cure this clutching issue. Then I found HPT and thought maybe there was some other setting in the ECU that would fix it... (rolled back the 3rd party tune of course, before fiddling with settings using HPT).

I've asked the dealer but they kind of said it's normal, but I didn't push real hard at the time. My stepdad agrees with me that something's weird/wrong with the car; it lurches and bogs for him too as he's letting the clutch out, and he's stalled it like I do occasionally, and we've both driven sticks for decades without issues.

One of the threads I copied above, mentions a 'clutch valve delete' but I haven't looked into trying it:

https://forum.hptuners.com/showthrea...en-shifts-6spd

Maybe I should go back to the dealer and press them to pinpoint this... I guess it couldn't hurt at this point. Like you said, maybe there's a hardware defect or bad sensor that's been messing with the ECU all along?

Thanks for the replies, and no worries about being delicate -- if I'm missing something obvious and I get smacked in the face with it, I'll be just as happy if I can get this thing fixed

[SiriusC1024]

Sounds like the bucking issue I had due to spark changing so rapidly for a small change in RPM.

Wonder if this will do it for you. I took a lot of the abrupt transitions out of the spark and cam tables. If so, you can refine it further.

[paul_z28]

Hey thanks a lot for setting that up, it's an interesting set of changes... I've noticed sharp changes in some of the tables like that too and wondered why it's set up that way on the stock tune. I'll give this a try on the weekend and will report back.

I haven't found any tables in HPT that deal specifically with the manual clutch being in or out... all I see is torque management stuff that relates to park/neutral, so I've wondered if the ECU is getting confused about what gear the car is in, until the clutch is all the way out.

On the other hand, with the gas pedal held steady as I release the clutch, the load on the motor is obviously increasing, and maybe that's pushing it past some of those transitions in the spark/cam/other tables like you had, causing the jump in engine output, and throwing it into torque management back and forth...

[SiriusC1024]

On the other hand, with the gas pedal held steady as I release the clutch, the load on the motor is obviously increasing, and maybe that's pushing it past some of those transitions in the spark/cam/other tables like you had, causing the jump in engine output, and throwing it into torque management back and forth...

My thoughts exactly.

[paul_z28]

I finally got time to work on this some more... I've been driving for the last month or so with SiriusC1024's tune, and I think it's a little better but the fundamental problem is still there.

As I'm releasing the clutch at takeoff or when shifting gears, there's still this half-second hesitation where the RPMs shoot up and down.

I grabbed some more logs with some additional pids from blindsquirrel's suggestions. Attached is a log (test15.hpl) that shows how the problem is still occurring. For example, look at 11:29:33.700 to 11:29:34.100.

* At takeoff, I'm bringing the accel pedal straight to 11% and holding it steady while gradually releasing the clutch pedal.

* During that time, driver pedal/final axle torque request shoots up to about 2,000 lb-ft and then dips back down -- why? Is this normal to request so much torque for 11% pedal?

* Along with that, for 11% pedal it goes to 44.3% throttle position, and then eventually settles down to 21% or so.

* Spark advance is shooting up and down as well, and TM advance is all over the place -- it goes positive, negative... I can't see any rhyme or reason to what the TM advance is doing.

Why does it request so much torque and throttle for only 11% pedal? Note that I have not touched the DD tables at all, and they all look reasonable to me. It's not going into PE either, nor should it at 11% pedal.

It's not requesting any TCS torque that I see. The Engine Torque pid, for 11% pedal, is up to 161 lb-ft, which does exceed Max Engine Torque, so that's why TM is kicking in, I bet. But I don't see why it's requesting that much torque in the first place.

It's as if when I'm releasing the clutch, it's trying to 'help' me by requesting extra axle torque or something.

Then, the extra-high torque demand is hitting a torque limit somewhere and sending it into TM.

I submitted a ticket to see if HPT can add some missing tables having to do with torque management, so I can try to narrow it down. For example, I don't have the Max Torque per Gear or ETC tip-in limit tables at all, maybe those would help.

If anyone else sees anything I'm missing, I would appreciate if you share it...

Log file (test15.hpl): test15.hpl
Screen shot: post_10_2023.png

[blindsquirrel]

I would go prowl around local car lots to see if I could find one same year/engine/trans and ask nicely for a test drive (make up whatever story you think would be most useful). GM has made some dumb garbage over the years, but the way you've described it there's no way these wouldn't have all been recalled and fixed.

Speaking of recalls, have you checked for TSBs/recalls?

[SiriusC1024]

Ah ok. Have you investigated Idle>Torque settings? External Load seems like a good place to start. Take values for 550-1400 rpm and multiply by .45. That's what I'd try.

[CYN_CRVR]

* During that time, driver pedal/final axle torque request shoots up to about 2,000 lb-ft and then dips back down -- why? Is this normal to request so much torque for 11% pedal?

Keep in mind that's axle torque. If you divide that number by your 1st gear ratio, and divide again by your differential ratio, it comes to ~140 lb-ft at the crank, which is in line with the various torque pids you logged that are in the 100-200 lb-ft range.

Have you tried disabling traction control?