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Author Topic: Rough running in a small rpm range.  (Read 888 times)

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Offline timlange3

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Rough running in a small rpm range.
« on: September 01, 2013, 07:28:36 PM »
Hi, I scanned for any codes, there are none, never had a CEL light on, (it comes on at start so I know the light works).

This is a 2007 Solstice GXP, 2.0L, manual transmission, no tune, no engine work, all stock.  Air filter and oil changed yearly, about every 6,000 miles.  Always use premium gas.  Currently have 61,000 miles on the car.  Usually driven about once a week and when not, kept in garage.

From about 1900 to 1950 rpm the engine runs rough, I would even say it is missing, it is that rough.  From idle to 1900 and from 1950 on up smooth as silk.  This happens when only maintaining speed, not accelerating, when accelerating, at any rate, through this range I notice no roughness.  When decelerating through this range I notice no roughness.

I would say it is getting worse very gradually.  Noticed it early last year, but could not really tell from running rough to road conditions, now my wife notices it too.  The rpm range for the roughness has not changed.  This happens hot or cold, happens right after start up and will continue all day during hours of driving.

Mechanic suggested to try Seafoam.  I now have a can in the car now, half a tank still to go and no change.

Replaced the battery this last January, so I believe you can consider the ECM to be 'reset' then.

Any thoughts or suggestions?

Thanks,

Tim.
Tim.

Offline LatinVenom

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Re: Rough running in a small rpm range.
« Reply #1 on: September 02, 2013, 04:28:16 PM »
Someone else had a similar issue and it was cleared by having a professional shop do the internal engine cleaning.
He did the same thing you did and it did not work.
Solstice GXP 2007.
Aggressive and fully loaded.
Mods: Magnaflow 2.5" exhaust, DDM Backbone & ProBeam,ZOK suspension,LV Kappa Front Chassis Brace, BTF Turbo Upgraded Wheel, Windristrictor, JPM Center console,arms,tulip,side doors,DDM Upgraded wheel tune.

Offline fiziksgxp

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Re: Rough running in a small rpm range.
« Reply #2 on: September 04, 2013, 12:01:42 AM »
Tim ... Seems they're discussing something similar to this over on the Cobalt SS side ... same engine ...

http://www.cobaltss.net/forums/2-0l-lnf-performance-tech-153/rough-idle-201101/


Offline elff

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Re: Rough running in a small rpm range.
« Reply #3 on: September 04, 2013, 09:39:18 AM »
You can monitor the misfires with a couple of different tools.
If you are getting random misfires on all cylinders, there is a very good chance that you have carbon buildup on the intake valves.
You would have to pull at least the Intake manifold to take a look and then have a shop do as LV advised

 

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