Chevy Cobalt LT 2.2 RPM Bounce Issue

Asked by Cayden May 19, 2019 at 07:57 PM about the 2009 Chevrolet Cobalt LT Team Canada Edition Coupe FWD

Question type: Maintenance & Repair

I have a 2009 chevy cobalt lt 2.2 litre engine. It has many mods that were not
done by me, I'm the second owner. It has 105000km. It has a supercharger,
coolant for the supercharger, some gauges that aren't hooked up, fully
custom exhaust. It was essentially modded to be a Cobalt SS. The problem
that I'm having has been going on for some time now. Whenever I'm driving
and depress the clutch fully to make it go into an idle state, at first the RPM
will bounce down to around 500-600 rpm and come back up to its normal
idle(around 750-900). Sometimes itll bounce around in the 500-800 range
and come back to normal. When this happens i can audibly hear the change
in sound from the exhaust, sounds like its close to stalling. I've tried cleaning
the throttle body, even completely replaced it, changed plugs and just some
general cleaning around the engine bay. I don't think there's any vacuum
leaks. Nothing noticeable anyway. When just idling the car runs completely
fine, it's only when i depress the clutch completely when coming to a stop
sign or something that it bounces around. It appears that it's getting worse,
only thing i can think of is that it might have a bad o2 sensor. both the o2
sensors are pretty jumpy as far as readings go, im not sure what they're
exactly supposed to read anyway. Could also possibly be MAF sensor
related. Thanks

1 Answer

18,685

Could be a lot of things. If its been partially modded by others and there are dangling wires and things not hooked up it could be most anything. I'd go through everything and try to determine what you're working with before spending any money on parts. Try scanning it for trouble codes. There may be some clues there. Also be careful when you do get it going. A 2.2 is not designed to be supercharged so go easy on it. On the other hand, it may actually be a 2.0, which was. Good luck. Sound like it could be a fun car if you can get the bugs worked out of it.

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