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2003 Chevy Silverado 1500 Runs Horrible

Jacob11531

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Jacob11531 Enthusiast

Jacob11531

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Hey everyone!

To start this off this truck is a 2003 Chevy Silverado 1500 4.8L 210K Miles and has been in Florida its whole life. 

 

I bought this truck in Florida in June and it ran great driving it back to Illinois. Ever since it started to get cold out (below 60Fahrenheit) the engine light would come on and flash here and there. When i sat at a red light and let it move at idle speed it would be around 500 rpm running very rough and shaky to the point where the truck shook me inside like crazy. It seemed to me like it was misfireing but this roughness would only happen at certain times like it got a wiff of cold air or something. (I know the flash means it is a misfire) I got the codes checked and it read lean in bank 1 and bank 2 and also misfiring (did not say what cylinders). When it gets up past 60Fahrenheit the engine light would go off and it stopped misfiring.

 

Here is what I have done so far:

I cleaned the Mass Airflow Sensor

I replaced all 4 o2 sensors and they did nothing. 

I then thought it was coil packs and wires so I replaced all 8 packs and wires yesterday and this morning going to work it ran worse than it has ever been before.

 

Sorry for the long post but i will appreciate any help to get this problem fixed.

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sdeeter19555 Senior Enthusiast

sdeeter19555

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Posted
Hey everyone!
To start this off this truck is a 2003 Chevy Silverado 1500 4.8L 210K Miles and has been in Florida its whole life. 
 
I bought this truck in Florida in June and it ran great driving it back to Illinois. Ever since it started to get cold out (below 60Fahrenheit) the engine light would come on and flash here and there. When i sat at a red light and let it move at idle speed it would be around 500 rpm running very rough and shaky to the point where the truck shook me inside like crazy. It seemed to me like it was misfireing but this roughness would only happen at certain times like it got a wiff of cold air or something. (I know the flash means it is a misfire) I got the codes checked and it read lean in bank 1 and bank 2 and also misfiring (did not say what cylinders). When it gets up past 60Fahrenheit the engine light would go off and it stopped misfiring.
 
Here is what I have done so far:
I cleaned the Mass Airflow Sensor
I replaced all 4 o2 sensors and they did nothing. 
I then thought it was coil packs and wires so I replaced all 8 packs and wires yesterday and this morning going to work it ran worse than it has ever been before.
 
Sorry for the long post but i will appreciate any help to get this problem fixed.
Plugs too?

Steve
2012 2500hd 6.0l

dewfpo Senior Enthusiast

dewfpo

Posted
Posted

Can you check the engine coolant temperature sensor, Intake air sensor, etc....?


DEWFPO

txab Senior Enthusiast

txab

Posted
Posted

Also check any intake connections. Make sure they sound and tight. Hose clamps, etc.....  But gasket are prone to leak, especially if they are the original from factory. They have an improved gasket available

davester Senior Enthusiast

davester

Posted
Posted

exhaust leaking can also cause a lean condition (bolts on exhaust manifold break off is common, but also check the manifold to exhaust pipe connection and for holes in exhaust).

Jacob11531 Enthusiast

Jacob11531

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The exhaust manifold seems ok and the engine is very clean besides a small leak by an oil pan gasket which i will replace next year so besides that there is not many leaks i can see if that helps.

It does have an aftermarket flowmaster exhaust if the brand is correct. 

Colossus Senior Enthusiast

Colossus

Posted
Posted
7 hours ago, Jacob11531 said:

I did not do plugs becuase they looked new and the dealer i got it from said they were replaced. 

Pull em out anyway.  Looks can be deceiving. 

dewfpo Senior Enthusiast

dewfpo

Posted
Posted
7 hours ago, Jacob11531 said:

Not sure? Would a code tell me that? How can i test it?

I use an Ultragauge to check all the sensors.   I'm sure there's an app you can use with your cellphone, you'd need the app and a dongle to connect to the OBDII port.  Others here know more about that than me and they can give you better advice.

 

For example.  My Ultragauge shows, ambient temp, engine coolant temp, trans temp and intake air temp.  On a cold start, they should all match with a couple of degrees.

 

DEWFPO

Jacob11531 Enthusiast

Jacob11531

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I am going to replace the fuel filter tomorrow and ill check the plugs. I was going to buy an obd2 scanner eventualy but not now because of the holidays. Can i have a parts store also check my sensors? I know it wont be when its completely cold but maybe it will show something.

davester Senior Enthusiast

davester

Posted
Posted
4 hours ago, Jacob11531 said:

The exhaust manifold seems ok and the engine is very clean besides a small leak by an oil pan gasket which i will replace next year so besides that there is not many leaks i can see if that helps.

It does have an aftermarket flowmaster exhaust if the brand is correct. 

Are all the bolts present on both exhaust manifolds?  Are you sure there is a crush-gasket where the exhaust manifold joins with the exhaust pipe on both sides?

 

Air can get in cracks you can't readily see.

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