Spark Knock?

[jtstacy77]

I recently traded my 04 silverado, for an 06 avalanche 4x4 with the 5.3. I have noticed that under load or going uphill I sometimes have a faint knock from the motor. It has 81000 miles on it. I never heard this noise in my silverado 5.3, but I did have a flowmaster exhaust that possilby kept me from hearing it. This motor is a flex fuel and my 04 wasn't. Just wondering if it may be spark knock or valves. I haven't gotten a check engine light with the knock. Could it possibly be the 87 octane with 10% ethanol. Any help is appreciated.

[music]

My '99 5.3 did that sometimes on 87 oct, under load (valves rattling). An aggressive non-oem tune could do it too, I'd guess.

[kdixer]

Try some fuel system cleaner and some higher octane fuel. Spark knock and valve chatter can sound alot alike. But spark knock is usually at heavy throttle under a load. Valve chatter or "float" is usually at high rpm's near redline. If it were lifters ticking you could here it at idle.

 

I would say it is most likely spark knock. To correct it just do the normal tune up stuff like air filter, fuel system treatment, MAF cleaner and you may check your plugs but they are supposed to be good to 100k. Gas is not what it used to be so even 89 can potentially solve it if everything else is mechanically sound.

[jtstacy77]

Try some fuel system cleaner and some higher octane fuel. Spark knock and valve chatter can sound alot alike. But spark knock is usually at heavy throttle under a load. Valve chatter or "float" is usually at high rpm's near redline. If it were lifters ticking you could here it at idle.

 

I would say it is most likely spark knock. To correct it just do the normal tune up stuff like air filter, fuel system treatment, MAF cleaner and you may check your plugs but they are supposed to be good to 100k. Gas is not what it used to be so even 89 can potentially solve it if everything else is mechanically sound.

 

 

I added a fuel system cleaner today, gonna see if it helps! Thanks for the input.

[dewfpo]

Another possibility is a knock sensor going out.

 

DEWFPO

[rebelman06]

My 2006 5.3 shows knock on my Aeroforce when I go up hills/overpasses/rough patches that load the engine up on the interstate. I don't see a lot accelerating around town, just on the interstate. I don't hear the engine knock, but the computer is showing it.

[Debo511]

Put a couple of bottles of Techron fuel system cleaner in the tank.

[SouthCo]

If the cleaner doesn't help, try going to 89 octane.

[CapitalTruck]

If I don't want to have any knock I have to use 89 in my 4.8. 87 will have occasional knock. Nothing bad, I still use 87 all the time, but 89 makes it purr a little smoother.