Weird Flutter at Quarter to Half Throttle - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
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post #1 of 8 (permalink) Old 10-24-2016, 01:05 PM Thread Starter
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Weird Flutter at Quarter to Half Throttle

So, since I went supercharged, I've noticed that there's sometimes a weird flutter when I go between like quarter and half throttle. If I put my foot down and force the car to downshift, it doesn't seem to happen. I managed to get a video of it happening, so if someone could help me identify the noise, that'd be helpful!

Weird Flutter - Sendvid

---------- Post added at 03:05 PM ---------- Previous post was at 03:03 PM ----------


IDK if that "Sendvid" website is very good, but I was feeling lazy and didn't want to log in to anything to upload a 3 second video.

If I could post it as an attachment here, I would, but it looks like I don't have the permissions to do that :/


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post #2 of 8 (permalink) Old 10-24-2016, 06:26 PM
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Oh shit.....never heard that before...could it be the throttle response is loose or something between there?

Be Happy!
2010 Chevy Cobalt LT: K&N Air Intake, removed chevy emblem on the back, blacked out the chevy bowtie upfront, Red LED Underglow, '08+ FE5 Struts/Shocks, Eibach Pro-kit Lowering Springs.
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post #3 of 8 (permalink) Old 10-24-2016, 07:12 PM
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throttle response is loose
Help me here. Where is that part? Or did I just not understand?

Could it be the same thing as a throttle plate?
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post #4 of 8 (permalink) Old 10-24-2016, 09:09 PM
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Quote:
Originally Posted by 1966tbird View Post
Help me here. Where is that part? Or did I just not understand?

Could it be the same thing as a throttle plate?
I meant the throttle sensor that monitor the throttle valve. I just forgot what it was called at the time, and im not sure if our cars have them.

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2010 Chevy Cobalt LT: K&N Air Intake, removed chevy emblem on the back, blacked out the chevy bowtie upfront, Red LED Underglow, '08+ FE5 Struts/Shocks, Eibach Pro-kit Lowering Springs.
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post #5 of 8 (permalink) Old 10-24-2016, 09:23 PM Thread Starter
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Our cars definitely have them. Version 1 of my supercharged tune threw a CEL for it. That might be it, but I kinda feel like that's not it, since the throttle body is brand new.


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Believe me, these cars have a habit of growing on their owners. Your feelings will only strengthen over time...
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post #6 of 8 (permalink) Old 10-24-2016, 11:18 PM
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Well parthros
U best hurry. There in North Texas, the Artic Winter could start at any time, then again your just as likely to be running around in cut-off in the mid 70s in Jan. You already know that the barbed wire fence across the kansas border makes a lousy wind break.

Now at part trottle, what is your nominal boost, & RPM that your noticing the flutter?
Is it constant at a certain rpm or noticable as you pass through a certain rpm?


Might you be feeling ignition: as in that majic pressure/fuel mix where you can find a week coil? I thought you had an extra parts.
Any chance you have set of coils?
Didnt i read you are running 1 step colder plugs, yes?
And you know,you have good 93 fuel?

Does OKC check for cats on inspection? If not, and your not running cats, head over to Wiley Post, or guthrie-edmond regional and score 5-10gal of 100ll .....for your lawn mower....errr garden tractor.....weed-waxker...whatever.
Mind you, O2 sensors will not like this for long but they will work...for a while..
you can deal with and test non working sensor. Pita to crawl under but still workable.

Now you might some help from,a shop on the broadway extension in Edmond...Think it is called Mike's
Check that, it is called Metric Motors 2608 South Broadway | Edmond, OK 73013

---------- Post added at 06:18 AM ---------- Previous post was at 05:53 AM ----------

To me, it sounds like only 3 cylinders are hitting.

Last edited by 1966tbird; 10-24-2016 at 11:24 PM.
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post #7 of 8 (permalink) Old 10-25-2016, 07:41 AM Thread Starter
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Ok man, that's a lot of questions. I'll try to answer some.
  • Video should answer the question about RPM range for the flutter. Doesn't happen at all unless I was cruising first. So, from a dead stop, going through the gears, it doesn't ever flutter.
  • Boost peaked at 11.25 psi on the dyno. Gauge says it peaks at like 13 or 14 psi, but I'm not confidant the gauge is accurate.
  • I think the coil pack is stock.
  • I'm running the spark plugs that come with the ZZP SC kit, which are Autolite XP5263.
  • I'm on a 91 tune, and 93 is extremely rare in Oklahoma. Pretty sure last fill up was 0% Ethanol.
  • Oklahoma does not have any inspections at all, however I did opt for a 200 cell cat.


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post #8 of 8 (permalink) Old 10-25-2016, 09:38 AM
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I ran your video clip a dozen times and saw the answr to several of my questions. Zeroed out a few. To me it still sounds like 3 cylinders.
Going back to re review your setup. Before going out to install my sway bar and i-shaft.
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