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2004 Silverado 5.3 rough idle

mantamac

By mantamac
in Ask A GM Technician

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mantamac New Member

mantamac

Posted
Posted

Hello gentlemen! and maybe ladies,

 

I have a 2004 Silverado, 5.3 liter gas only, with problems, It began with Knock Sensors low voltage. Both were replaced. No luck! I replaced the knock sensor harness, no luck. My reader still shows lo voltage on sensors bank 1 & 2. I had a suggestion to replace the O2 sensors. Even though it's not showing on the code reader, i was told to change them. On my reader, I have a live data view and Banks 1 & 2, upstream Sensor are reading all over the place. It's almost a saw tooth pattern. Is this normal?

 

At idle, it misses randomly. At full throttle, it bucks pretty bad. Anywhere in between, its good. I'm an old carburetor and points man, so this new fangled technology is leaving me scratching my head!

 

 

I attached the readings. Please HELP!

 

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post-156520-0-61286400-1459464703_thumb.png

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted

That looks normal to me for a pre-cat sensor. If it's switching, it's good. Lingering high or low (lazy switching) indicates a bad sensor.

 

Beyond that, I'm in the same boat as you. I just rode my '74 Yamaha RD350 today - carburetors & dual-point ignition. It's a thing of beauty. Got to watch the throttle in 1st gear - that wheel comes up at the speed of light! :D

 

At least this will give your post a bump, so maybe someone who knows these electronic wonders can help you. Good luck. :cheers:

Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted

Back when EFI came out I was told to think of the various sensors by the job they do. For example, TPS is like a accelerator pump on a carb, it tells the ECM that the throttle is being opened. The MAP sensor is also in this area. Each sensor replaces some mechanical part in the Carb/Distributor engines.

 

Did you see this thread? http://www.gm-trucks.com/forums/topic/153096-2005-gmc-sierra-1500-p0332-specific-knock-sensor-questions-inside/

 

Did you use GM branded parts or generic parts from auto parts store?

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted

Boy, that's a hell of a place to put a pair of sensors! Well done, GM ... :banghead:

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