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Discussion Starter #1
I am having a problem with my 06 cobalt LS with 115K miles on it. About two weeks ago car was running very badly, no pick up and took forever to get up to speed. CEL was blinking at first then went solid after 15 minutes. Took car and had code read, P0300 random misfire. Removed gas cap and tightened back on, no fix. Used the car that night and it ran fine for about 30 minutes and then started acting up again, the CEL is on the entire time.

Replaced spark plugs (no gap required plugs) , the next day I get gas and make one stop, turn car off and on and the CEL goes away and car runs fine for about 8 days.

Now the CEL is back on, car has absolutely no power, almost stalls at idle. I put seafoam in the gas tank, no luck.

Also, there is a smell of like burning rubber(and not the tires) and the exhaust sounds rough.

Not looking to throw a lot of money on the car. Bought the car with 75Km and besides changing the oil, oil and air filter haven't done anything else, besides the plugs mention above.

Thanks for the help.
 

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Maybe , if you smell rubber, that, one of the wiring harness in the back of the engine came out of its loom armour and touching manifold.
 

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I haven't pulled them, will do that today.

Is there any way to test the catalyst convertor or shouldn't I even be worried about that?

Thanks

---------- Post added at 07:09 AM ---------- Previous post was at 07:02 AM ----------

I only smell the rubber when the car is running rough, otherwise there is no smell.

---------- Post added at 07:19 AM ---------- Previous post was at 07:09 AM ----------

OK, just started car, it is running fine now. CEL is still on. The car is driven about 50 miles one way to work every day. This started again about 30 miles into the trip back home.

When it first started about two weeks ago, same thing, ran rough on the way home, after it sat overnight it ran ok.


Could it be something failing after the car heats up?
 

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I would definitely check for rubbing wires close to manifold like HO2 sensor wires.

---------- Post added at 10:42 AM ---------- Previous post was at 10:41 AM ----------

What was the code this time?
 

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I say find the source of that burning rubber smell and you will be very close to your problem. Because burning rubber is not good unless it's your tires.
 

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Discussion Starter #10
CPS????

Yes when it has no power the CEL does flash a few times then will go solid for a minute then do a few flashes then go solid again, it will repeat this cycle.

I just replaced the coil pack and the fuel filter. Drove it for about 25 minutes, it ran fine. the CEL was on solid. I stopped twice to shut the car off, to see if it would start acting up. On the second stop upon start up the CEL light went off. Drove it about 15 minutes to home and had no issues.

Keeping my fingers crossed that it is fixed. I'll be back if this doesn't work.

Thanks everyone!!

Joel
 

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Well coil pack would be the norm for your model year and mileage, just don't know what the burning rubber smell has to do with it unless what you were really smelling was the glyptol insullating the windings in the coil pack.
 

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Discussion Starter #12
ok, the coil pack was the winner. Bought a new one and now the CEL is gone and it runs fine.

Well actually better than fine. It is idling at about 1500, using almost the double the gas. I cleaned the throttle body but still the idle is still high.

Any suggestions?
 

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Might have a leaky intake after throttle body.
 

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Discussion Starter #14
If I turn the Ac on the Idle drops to 1000 and pretty stays there, if I turn the AC off and DON'T hit the gas it stays there, but as soon as I hit the gas with the ac off it goes back up to 1500.
 

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Might have contaminated HO2s when coil pack was acting up. Clear the code and wait and see if it will come back. It might clean itself out.

DTC Descriptor
DTC P0420: Catalyst System Low Efficiency


Circuit/System Description
Important: A new converter with less than 100 miles on it may set DTC P0420 due to out-gassing of the internal matting. Operating the vehicle at highway speeds for approximately 1 hour may correct the condition.

A 3-way catalytic converter (TWC) controls emissions by converting hydrocarbons (HC) and carbon monoxide (CO) into carbon dioxide (CO2), and oxides of nitrogen (NOx) into nitrogen. The TWC also stores oxygen. When the listed driving conditions are met, the Catalyst System Efficiency test will run. The powertrain control module (PCM) monitors this oxygen storage capacity by comparing the pre and post-catalyst oxygen sensor signals while adding and subtracting fuel during specific driving conditions. The PCM compares the pre and post-catalyst oxygen sensor signals to determine if the oxygen storage capacity of the catalyst is degraded.
 

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Discussion Starter #17
It stills has the high idle. Going to disconnect the battery today for about 30 minutes to see if that will reset the programming. It should also clear the code.
 

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Discussion Starter #18
Ok the battery trick didn't work, the code came back after about 50 miles. The idle is still around 1500.
 
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