[c5jako]

So I've done my searching, please let me know if I missed the big thread on this. Since I bought my 2017 SS 1LE 6M I've been unhappy with the throttle on the street. Not just the lag, I fixed that with a Soler TB and controller. Great product (I like CF-4 for daily), I can dial in the mapping easy and I love the increased low-end response but it didn't fix the inaccuracy of throttle position.

The car is a joy on the track, so smooth and does exactly what I want. Spirited driving on the street feels great. However, I can't drive that way all the time. Shallow throttle and maintenance throttle between 1500-300 rpm at <20% produces bumpy acceleration. It will hesitate and wabble (like you're tap dancing on the pedal). This is not that A8 TC issue, this is not a cold start or slip/traction issue. It happens randomly any time, TC on or off, even with the "long hold" TC/SC off.

Now, I have had intermittent problems with the camshaft sensor CEL, but this throttle issue occurs so often, without throwing a code for weeks on end, that I have a problem blaming that. Plus, I don't want to remove my TB/controller to take it back to the dealer.

I'm about to buy an new OE throttle pedal from Rock Auto to continue my process of elimination, but figured I'd post here first. - Thanks for any advice.

[arpad_m]

Originally Posted by c5jako

So I've done my searching, please let me know if I missed the big thread on this. Since I bought my 2017 SS 1LE 6M I've been unhappy with the throttle on the street. Not just the lag, I fixed that with a Soler TB and controller. Great product (I like CF-4 for daily), I can dial in the mapping easy and I love the increased low-end response but it didn't fix the inaccuracy of throttle position.

The car is a joy on the track, so smooth and does exactly what I want. Spirited driving on the street feels great. However, I can't drive that way all the time. Shallow throttle and maintenance throttle between 1500-300 rpm at <20% produces bumpy acceleration. It will hesitate and wabble (like you're tap dancing on the pedal). This is not that A8 TC issue, this is not a cold start or slip/traction issue. It happens randomly any time, TC on or off, even with the "long hold" TC/SC off.

Now, I have had intermittent problems with the camshaft sensor CEL, but this throttle issue occurs so often, without throwing a code for weeks on end, that I have a problem blaming that. Plus, I don't want to remove my TB/controller to take it back to the dealer.

I'm about to buy an new OE throttle pedal from Rock Auto to continue my process of elimination, but figured I'd post here first. - Thanks for any advice.

Assuming that this happens even in track mode whose throttle mapping is the only one resembling a linear curve, I'd first data log the issue with HP Tuners and look at all the associated channels (pedal position, commanded throttle actuator, SAE throttle position etc.) to see where this jerkiness may be coming from.

If the position sensor value varies while you're keeping your foot in the same position, switching out the pedal assembly may help.

No other ideas apart from this, hopefully someone else can also chime in to help. Good luck

[c5jako]

Originally Posted by arpad_m

...I'd first data log the issue with HP Tuners and look at all the associated channels (pedal position, commanded throttle actuator, SAE throttle position etc.) to see where this jerkiness may be coming from.

If the position sensor value varies while you're keeping your foot in the same position, switching out the pedal assembly may help.

Thanks, it seems to do that. I feel like my foot is static on the pedal with slight pressure, and it's slowly coming up through the lower revs, when it bobbles for no reason. Probably would be good to get a log of the throttle response to the pedal action to see if there are any spikes or dropouts, but I think that would just bring me back to the pedal assembly anyway.

This isn't the car I'm supposed to be working on, I have the LS3 arriving next week for my C5 swap!

[arpad_m]

Originally Posted by c5jako

Thanks, it seems to do that. I feel like my foot is static on the pedal with slight pressure, and it's slowly coming up through the lower revs, when it bobbles for no reason. Probably would be good to get a log of the throttle response to the pedal action to see if there are any spikes or dropouts, but I think that would just bring me back to the pedal assembly anyway.

This isn't the car I'm supposed to be working on, I have the LS3 arriving next week for my C5 swap!

Let me know if you have trouble sourcing a new pedal assy, I have a spare lying around in perfect condition.

[c5jako]

So I installed a new accelerator pedal, no difference. It seems so random, at times I'll do a whole commute without it happening, then it will happen 5 times in 2 minutes. It dips down for no reason, blips up for no reason. Not dangerous or anything, it's over so fast that it's just an annoyance, but man I hate being surprised by what my car does. It's all the more frustrating because I love everything else about this car.

I'll have to get some logging saved out to figure out what's going on. Never used the HPTuners stuff but want to look into it.

[Scargoes]

You need to pinpoint the item that is causing the problem, Start with taking the Throttle Controller off. Still there, put the stock TB back on, still there then it's time to go to the dealership.

There were some people having surging issues with the ported TB and Soler was pretty good about working to fix the problem with them. Maybe you have that problem too, just a thought.

[c5jako]

Thanks Scargoes, that's my plan, kept the OE TB for that reason. Just might take a while to get there so looking for any other tidbit of wisdom that could be the silver bullet I'm looking for.

[JitteryJoe]

I'm curious to see what the resolution is here. My brand new 2021 seems to hesitate when giving additional throttle and does seem jumpy at times. I was going to mention that and the Clutch rattle when taking it out of gear.

[c5jako]

For anyone watching this, I finally got the car to the dealer today to have it checked out. After dealing with it for a year, I can't handle it anymore. Come to find out that any reprogramming or PCM work may not be covered by the powertrain warranty (isn't the word Powertrain in PCM?). I just hope the tech that takes it for a spin is able to feel the issue, it's so inconsistent. One way I found to always get some weirdness is to start at 2K RPM and slowly roll on the throttle - the hesitation and surge is definitely noticeable. I could deal with it if that was the only problem, it's the slight off-throttle buck and blip that drives me crazy. My cammed and tuned LS3 is velvet smooth compared to this engine.

[AutoPenalti]

Problem occurs with my A8 as well. It seems to want to do that every so often especially when going from first to second and the bumping acceleration as I changed to "faux manual". It's so pronounced that when I hit the gas off the line it starts to bump and I have to let go of the gas or else I feel that I'm to blow up the tranny. I learned to live with it and just wait until I have enough to purchase a ZL1 or a 2021 2SS with A10

[cmitchell17]

I am glad someone else notices this as well, my 2017 SS is the same way. I've tried smoothing the driver demand and all kinds of other stuff in HP Tuners, and I also have a Solar TB as well.

The "problem" is still there. I put problem in quotes because I think this is just the sorry way GM programed the car to drive. There are times I swear the throttle position has moved, and I have even tried to catch it on a log doing it and I see now change in accelerator, throttle, or timing or anything.

The absolute worst is trying to drive in a very slow stop and go traffic jam. Especially when you start from a dead stop and inching along below 10 mph in first gear and have to let off, then start going again. If I didn't have the years of driving experience in this car or someone else was driving, I am sure they would press the gas to go again and if the car was still in first you will get a huge jolt and whiplash. The 8L90 does have a pretty low first gear but I know there are better ways to program and compensate for these things for driveability.

One thing I have found that maybe helps just a little bit, is where you have your foot on the accelerator pedal. It is easy and usually more comfortable to drive with your foot pressing the very bottom of the pedal, which makes the throttle application more sensitive. If you move your foot so that it covers the entire pedal you can more slowly apply it and it seems like it helps some, but its uncomforatble and tires out your foot.

To me older cars were so much better at these little things. Like the GMT-800 trucks had accelerators with 2 degrees of freedom so that the flat part of the pedal would pivot on the end of the arm. If the Camaro had this it would give so much more throttle control in these situations, especially for a car with such a high dynamic range, meaning the car has so much power its harder to create the throttle mapping than say a car with half the power.

Additionally this car is so stiff as well it brings out all these issues worse than say a regular car. For example, a lot of the bushings on the axel and driveline and steering are stiffer to improve response and give a performance feel, but all this stuff makes these problems and NVH (noise, vibration, and harshness) so much worse.

[minesmuchlouder]

Also having this same issue with my 19' RS. Its jumpy sometimes and feels like I'm moving the pedal up and down when I'm actually just keeping it steady. I put it on cruise control and slowly ticking the speed up from 40-50 and you can still see the rpm fluctuate just like you were saying. I have a Solar TC too. I've removed the controller and that did not fix the issue. Maybe it just one of those things we'll have to deal with. It sucks but I still love the car

[BADLUK007]

I'm having same issue, it surges it first gear very noticeably and second but it's not as noticeable. I was thinking about pulling the plugs and checking them out and go from there. It's very annoying as if it's releasing the lower incrementally.

2019 ss 1le m6 all stock 38k miles

[c5jako]

I haven't visited this thread for a while, and honestly just been dealing with the issue. It's exactly as @cmitchell17 describes - I don't know how I would daily this car if I had a commute with any slow moving traffic. I went to the dealer and everything checks out of course, no issues.

Recently I decided to pick up the troubleshooting again, so I did some data capture with VCM Scanner. After many smaller blips and dips, I captured a decent one that I did not call for with the accelerator. See the image attached.

Blip1 shows a very quick tap on the accelerator. Looks normal, except there was no input like that from the driver. I was performing some slow coast-down and slight throttle application to sustain speed (that's when the blip normally happens). The accelerator reading rises from 19.2% (idle) to 35.9% and drops back down to 19.2% in about 200ms. Interesting to see that the car is actually responding to what it believes is an accelerator input, and it's not just a throttle movement gone rogue. This is different than the blip for downshifts, as there is no accelerator change during those (and of course the revs rise, this blip is too short to make engine speed jump). I have already replaced the accelerator pedal with no change, and I don't expect it's the pedal because the problem would be much more consistent.

This is discouraging because if the system is reading accelerator input when there is none, that's not going to improve with a tune adjustment. Only hope I think is to bypass the existing wiring harness direct to the control module? Is there a TAC module to replace in these cars?

Not all complaints - So great on track, especially after replacing the radius rod bearings with spherical.