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Discussion Starter #1
Hey guys. Me again. Thought I'd ask as you've been very helpful recently. Cobalt '05 with 148K on it.

A few weeks ago I brought it in due to bad idles and the car stalling a few times at lights or when slowing down. The mechanics caught no codes but did clean out a very dirty throttle body. For the past 2 weeks it's been running great: idling about 750 RPM.

Today, the RPMs dipped to well below 500 as I slowed to my driveway and the lights (headlights and gauges inside) dimmed. Since it's not the throttle body, could it be the MAF sensor? (I've been reading about this problem).

I am also going in to get a new fuel filter next week to be careful. Any ideas are greatly appreciated guys- this car is driving me crazy these past few months!
 

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Standard or auto?
 

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I cut stuff
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Just throwing this out there but if your lights are dimming I would get your alternator and battery checked. Make sure the charging system is working properly. If you have no juice your voltage for the ignition will be weak. I may be misleading you but it's just a thought.
 

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Like blazer said, easy stuff first (assuming you haven't looked at these already). Check your battery and alternator (corrosion, connections, belt tension, etc.) What problem have you been reading about with the MAF?
 

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Engine idling low is the cause of lights dimming and not the other way around. Wish I had more details on the symtoms. But I'm going to go with one of the rev-up sensors not working properly here. You have an 05 so a PCM. Do your brake lights work? It could be the PCM not telling the TCM that you're applying the brakes and therefore not releasing the torque converter and bogging down the engine. MAF is always a possibility though but that is really hard to diagnose from here, plus MAF will usually set a code if it works that bad.

Could also be moisture coming through the fuel line at the wrong time of your trip.

Just need more detail of symptoms and what's been done on it lately that might be the real cause.
 

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Levee
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Engine idling low is the cause of lights dimming and not the other way around. Wish I had more details on the symtoms. But I'm going to go with one of the rev-up sensors not working properly here. You have an 05 so a PCM. Do your brake lights work? It could be the PCM not telling the TCM that you're applying the brakes and therefore not releasing the torque converter and bogging down the engine. MAF is always a possibility though but that is really hard to diagnose from here, plus MAF will usually set a code if it works that bad.

Could also be moisture coming through the fuel line at the wrong time of your trip.

Just need more detail of symptoms and what's been done on it lately that might be the real cause.
This. And a lot of times, the MAF will not only throw a code, but if it was THAT dirty, you would notice it when you open your air filter box where the MAF is located. You can still clean it though, it never hurts to clean it, just use MAF cleaner specifically.

I'm still going to go with Coby on this one, if it has been running fine and just one time it fell like that then it could just be a little water in the fuel. Run some Sea Foam through your tank, that will help clean a lot of the Impurities out of your fuel system. Your car can run like you said if you have injectors sticking and putting WAY too much fuel in your cylinders (flooding out).

A little more info would be VERY helpful in this situation though.
 

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Discussion Starter #8
Thanks guys. Yea, it appears to have been only the one incident, and the tank was nearing a quarter. (I've kept it half full at least until this time !)

the air up here in Toronto is freezing too (-15C this week) so I will go with your thoughts on this and assume it's moisture.

Thanks for the tip on the Sea Foam. I'll give it a try.

Oh, and yea the brake lights work Coby, so I hope we've narrowed this down :p

Thanks again!
 

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Levee
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I live by Sea Foam in all my vehicles. so from a professional and personal opinion, it works fabulously.
 

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Seafoam will never steer you wrong
 

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Oh, and yea the brake lights work Coby, so I hope we've narrowed this down :p

Thanks again!
Yeah I looked it up same switch as brake lights but different contact.
 

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I'm going to collect some foam from the sea right now.
Stuff from Halifax Harbour is what you want. Its top quality stuff:toung:
 

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Discussion Starter #15
Hey all; back with good news. I finally had the fuel filter removed and changed and the old one was full of gunk. This new one, with the injector cleaner, has made the car run like brand new once again. Thanks again for all the tips guys.
 
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