Anyone out there willing to give me a brief explination about how the knock counter works, when the knock counter starts rolling and also some examples of what is a normal knock counter reading and what is bad or out of control? I would really appreciate it. Thanks.

Ken R. 95Z

 

I would also like some info on this, I am getting readings of 10-20,000 on startup and then it seems to stop getting higher.

 

The knock count is simply the amount of sounds that are considered "knock" by the knock sensor mounted in the engine block. The PCM will then take into consideration the variables that are used to scale back the timing (this is based on MANY factors, including but not limited to RPM, TPS%, low octane knock tables when using low octane gas, fast knock attack, and burst knock). The thing you are talking about at start up I have seen before, both on my car and my friend's car with a 383 stroker. My car no longer does it, I believe because my knock sensor was going bad and I have since replaced it (it also caused the knock sensor to randomly read knock but the PCM would not pull any timing, very strange to see happen). I've advised my friend to replace his knock sensor to see if it fixes the problem, but he has not replaced it yet. It is obviously false knock, because while data logging, once he takes off from a stop, the knock instantly disappears and there is no knock that is heard while the knock count is going up like crazy. If you haven't already, an LT4 knock module (the module that installs in the PCM) might help if you install one. They are only around $35 if you go to the right places.

 

Knock at engine startup is of no concern, the starter gear engaging the flywheel will cause the knock sensor to detect all kinds of noises. Burst knock may be detected and cause the counter to go up, but if you have adjusted burst knock retard down in the corresponding table, then no KR will show even though knock counts increase.

 

Knock at start up is just a test the pcm does at start up along with other sensor checks. This is normal. The pcm runs a quick check on all sensors.