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2005 Cobalt Coupe Base, Manual Trans, 155,000 km, bought used. I've owned this vehicle going on 8 years. It's always seemed to 'shudder' when I engage the clutch, or the RPM drop rapidly while slowing down. All lights dim, blower motor will come to a stop, but the car will always kick the RPM right back up to around 750, but the car never stalled so I never really looked into it. A few months ago this issue got worse and right after starting the car, misfire occurred and CEL light flashing. Got the car to start after 3 attempts and took to local shop. I replaced the spark plugs, cleared misfire code, car still seemed to shudder after repair and RPM drops low, but it never stalled again, until today. I live in the Prairies in Canada, so on a very cold day the temp can drop to -30 easily, so I'm thinking it could be temperature related, as the 1st misfire happened on a relatively cold day. Started the car after 9 hours of it not running and as usual, RPMs drop and without a shudder the car shuts off. I try starting it again and the same thing happens. Wait about 1 min and try again and the car starts no problem, drive all the way home (about 20 mins) without issue, aside from the RPM dropping, lights dimming, as usual. Battery was just replaced last year, but I was thinking charging system has an issue? I've noticed a few other threads with similar issues, but no real fix. Anyone have any suggestions? Thanks!

*Note* I have also been advised to have my timing chain/tensioner replaced, as I have the common rattling noise emerging from the engine. Haven't had this repair completed yet, but could it have something to do with my issue above?
 

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*Note* I have also been advised to have my timing chain/tensioner replaced, as I have the common rattling noise emerging from the engine. Haven't had this repair completed yet, but could it have something to do with my issue above?
Doubt if tensionner is the cause. But if you have ratteling upon start up change the tensionner before the chain jumps because then you're in big money.

When is the last time you cleaned the throttle body or had it cleaned?
 

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Get the cam chain fixed first. If idle speed still problem, it might be the throttle body air flow needs to be cleaned. Had that happen once on a jeep.
 

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Doubt if tensionner is the cause. But if you have ratteling upon start up change the tensionner before the chain jumps because then you're in big money.

When is the last time you cleaned the throttle body or had it cleaned?
i agree with coby...i have also herd that our cars start idling rough when the throttle body has build-up
 
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