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Discussion Starter #1
So, first off, I do have a code for the check engine light, but it's currently out in my car and I can't get to it until a little bit later, but I'll be happy to post it when I can.

A few days ago (Might have been Thanksgiving actually), I started hearing a knock/click sound from my '08 Cobalt from under the hood and at the same time, my check engine light came on and I had an obvious loss of engine power. It hasn't been too bad, but I have probably lost 30 to 40% of my acceleration, and I haven't received a "Reduced Engine Power" message on the HUD.

Now, I took it to autozone and when they read the codes, it came back as a "knock sensor condition" with a list of possible causes, and the guy who came out to check the code suggested that it could possibly need a valve adjustment.

Now, I haven't worked on any cars since 10 years ago in high school, but at 70K miles, is it possible that I could already have a valve problem? Also, from my understanding the timing is retarded automatically if the knock sensor trips, so if the knock sensor is malfunctioning, could it actually cause the knocking sound whenever it retards the timing?
 

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Opposite if knock sensor fails it will not retard timing and you will hear spark ping..Might be dirty contacts on the sensor so try cleaning them first.
 

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Discussion Starter #3
Thanks for the reply. So if I am hearing the knock, then it could be that the knock sensor is failing? Just want to make sure I read that correctly.
 

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Chevy Customer Service
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I see you're already getting some great feedback. If you do decide to go to a dealership to have this concern addressed, please let me know and I'll see if I can be of any assistance.

Best,
Sarah
GM Customer Service
 

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Discussion Starter #5
I see you're already getting some great feedback. If you do decide to go to a dealership to have this concern addressed, please let me know and I'll see if I can be of any assistance.

Best,
Sarah
GM Customer Service
Well, one thing I was trying to figure out is whether or not an engine knock would be covered under the factory warranty. I'm at 3 years and 70K miles and I was thinking the manufacturer warranty would cover anything engine related up to 5 years/100K miles, but I wanted to make sure this would fall in that category before I drive it up to a dealership.
 

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Sensors are excluded from powertrain coverage, per the 2009 Chevrolet Warranty Manual (p5).

The following engine components are covered:
" Engine Coverage includes: All internally lubricated
parts, the entire pressurized fuel system (in-tank fuel
pump, pressure lines, fuel rail(s), regulator, injectors and
return line). Also included are all actuators and electrical
components internal to the engine (i.e.: Active Fuel
Management Valve Lifter Oil Manifold, etc.) as well
as the Engine/Powertrain Control Module, module
programming, cylinder head, block, timing gears, timing
chain, timing cover, oil pump/oil pump housing, OHC
carriers, valve covers, oil pan, seals, gaskets, manifolds,
flywheel, water pump, harmonic balancer, engine mount,
starter motor, turbocharger and supercharger. Timing
belts are covered until the first scheduled maintenance
interval."

Hope this is helpful!
Sarah
GM Customer Service
 

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my cobalt started having lifter chatter or knocking right after i changed the oil. the check engine light came on so i took it to autozone and they said the light was from the knock sensor. i ordered one and it will be here this evening. does anybody know where it is in the motor and if it cures the lifter noise ill be sure to let every one know. oh and i have over 130,000 miles on it
 
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