[Brandon Gibson]

Hey guys brand new here, but.....

I've had my 2017 avalanche track and tech pack for a while and has been through two different set ups. Stock exhaust and then longtubes, both set ups have always had the problem with the knock sensor going crazy. It was around 6 degrees or more on the knock read out, but was recently lowered to about half a degree or so after switching to e85 and welding up a broken exhaust hangar. Tuned by lund and they think its a physical issue but I can't seem to find it . If any one has this problem or has fixed this problem please help!

 

[JimT]

Hey guys brand new here, but.....

I've had my 2017 avalanche track and tech pack for a while and has been through two different set ups. Stock exhaust and then longtubes, both set ups have always had the problem with the knock sensor going crazy. It was around 6 degrees or more on the knock read out, but was recently lowered to about half a degree or so after switching to e85 and welding up a broken exhaust hangar. Tuned by lund and they think its a physical issue but I can't seem to find it . If any one has this problem or has fixed this problem please help!

I have looked at this post multiple times and still question it.

Knock Sensors are designed to sense high frequency vibrations within the engine, i.e.: Engine Ping. Sensing these vibrations a signal (very small voltage) is sent to the Engine ECM which will interpret them as engine ping and make adjustments to engine function to eliminate that ping. Usually in the form of a reduction in ignition timing advance, but don’t think that valve timing can’t also become a factor. The diagnosis of this system is usually done using an Oscilliscope and it requires a knowledge of base frequencies the engine normally produces.

I don’t know the tune you have experimented with, but a reduction of your Octane Rating (to E85) seems counter productive it minimizing any engine ping, actually just the opposite. It the knock sensor is indeed sending bad signals to the ECM you need to concentrate on engine vibrations of the high frequency types. Again special equipment. I would take your car back to square one if you don’t have a donner car to compare and determine it you really have a problem or a self enduced one.

 

[driller]

... a reduction of your Octane Rating (to E85) seems counter productive it minimizing any engine ping, actually just the opposite.

E85 is very resistant to pinging.

If it were me, I would turn to the Vampire by J&S Electronics.