Jerking when pressing the gas after coasting - Saturn Sky Forums: Saturn Sky Forum
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post #1 of 6 (permalink) Old 09-13-2017, 12:22 AM Thread Starter
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Jerking when pressing the gas after coasting

Does anyone else experience a slight jerking while coasting in gear after having a performance tune? This doesn't happen all the time but when it does I am usually coasting in gear, any gear, and when I press the gas just slightly to speed up just a bit or keep my RPM's up I get a jerking (Fluttering) feeling, bouncing back and forth. The clutch pedal is not pressed in while coasting so I am just pressing the gas again. I know I feel the car engage throughout my shifting a bit when accelerating but that is due to the higher torque.

I have a manual 2008 Redline and the mods I have are as follows:

DDM Charge Tubes
Synapse BoV
K&N Typhoon Air Intake
In Person Tune

Thanks to everyone in advance!

Last edited by SevenDaySuffle; 09-13-2017 at 12:24 AM. Reason: Updating with Car information.
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post #2 of 6 (permalink) Old 09-13-2017, 08:42 AM
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Which tune do you have?

In my limited experience when you get searching just off idle its the transition table causing the problem. The tune is "hunting" for the proper settings and the data table does not support clean transition from idle to part throttle.

If you have a "canned" tune that is known to be good then you might look at cleaning the MAF, check the seals on the intake side to make sure you don't have any leaks, inspect the intercooler to make sure its not damaged or leaking or has trapped fluids inside it. Also take a look at the throttle body and make sure its clean and functioning well.

If you have a custom tune, check the above then if you still have the same issue take it back to the tuner. It should not bounce at low throttle.
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post #3 of 6 (permalink) Old 09-13-2017, 09:08 AM
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I was wonder what the cause of this might be. Will be interesting to see what our owners responses is, who do have the " tuned " performance mod in this case. Is it electrical with in the tune itself, or the ECM system or is it mechanical in nature? No problem with the clutch or the rear end? IF it's the tune, then the guys here will have an answer for it. I had thought it could be 2 things right off the bat, the MAF and maybe the intake/exhaust solenoids might be the cause? The TB could be the problem, but it has shown no issues before this problem rose it's ugly head before?

Not limp mode, no codes thrown? No boost issues? IF the tune is searching for idle to partial throttle, could a patch by the tuner mfg. by sent to the owner to resolve this? Tech support from the original source to rectify this, comes with the cost of the original purchase price?

Quick fix... don't coast in gear ever. Press your right foot down continuously. Does this happen when cruise control is used?

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post #4 of 6 (permalink) Old 09-13-2017, 10:46 AM Thread Starter
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I had a tuner very well known in the cobalt world tune my car in person. I felt like this was the best way to ensure I got a tune that was best for my car.

I discussed this with my tuner and he stated that this issue is generally due to the aftermarket BoV letting in unmetered air. The car drives great and is super fast when I am able to get into it and the car engages much better than it did stock.

I havenít had any problems with the clutch or the rear end that I am aware of. I havenít checked the MAF but I did replace the intake and exhaust solenoids less than a year ago.

After my tune while trying to find this issue I did end up throwing a code: P0335 for the Crankshaft A sensor. I ordered a new sensor, replaced it, and the Code went away. I thought that the bouncing had improved right after that sensor replacement a week ago but now its noticeable again.

No Limp mode, no codes currently, no boost issues. I think I can get the tuner to look at it, said he would, but he isnít an actual business, just a contractor from a business. Just want to make sure I cover my bases before bothering the tuner again.

Plus if this was the tune configuration wouldnít it do it every time I press the gas just a little bit?
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post #5 of 6 (permalink) Old 09-13-2017, 11:34 AM
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Again, I am not an expert but I have seen this on tuned cars before and its always been the tune while in transition to part throttle from idle hunting for the right settings. If its really pronounce the whole car can jerk as it goes from high power to idle power and back repetitively.

When I got my first tune the car would die when transitioning from decelerate to idle because the tuner had the tables overlapping. The idle table would not be accessed until the RPMs were already well below idle. The car would either just die or it would bounce from 600 or less RPM up to 1600 RPM then go up and down a few times till it finally transitioned to idle settings.

Its something happening in that transition region where the tune goes from one table or condition to another that is not coherent.

You can test the tuners hypothesis by taking the after market BOV out of the equation and running it "stock" and see if the problem goes away.

The fact that it runs well under high throttle settings is kind of irrelevant to your issue as its working off a different set of data. when I had my issue early on with transition to idle, I was told by several experts that full power settings are easy. Its the transitions and part throttle that cause the problems.
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post #6 of 6 (permalink) Old 09-13-2017, 12:05 PM Thread Starter
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Rob, thank you for that information. I am going to message my tuner and see if he can ride along with me so that I can show him when the issue occurs. Maybe then he will have an idea of where to look for this issue. I don't believe that the BoV is causing this issue because I checked with the person I bought it from and they did not have this issue when it was installed on their car.

Is their anything that the tuner could reference when trying to adjust the settings? Like the numbers from another tune or the "canned" tunes?
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