[jwzimm]

Hey all,

I have an issue I wanted to ask about. I was driving up a mountain road the other day quite slowly (GF was in the car). I could hear the engine knocking/pinging quite a lot. I was only at part throttle in 2nd and 1st gear so I was not pushing the engine at all.

I have also experienced what I thought was a major knock event during an uphill full throttle pull. I hit it in 2nd gear and the car pulled as expected but I heard what sounded like several aerosol cans being shaken. No engine light or any indication from the dash though. I pulled codes when I got home and had none.

I was told these engines and the DME are excellent at pulling timing and quelling knock before you every hear it. This is counter to what I was seeing though. It makes me nervous. This is all on Map 1 on my JB4.

It is possible that one of the knock sensors is unplugged or bad? I am not sure how the knock sensors work but I would assume that the DME would see if it is not connected but I may be wrong. Any other thoughts on possible issues?

[mike@x-ph.com]

Try and log it to see if you are having any cylinder timing issues

[jwzimm]

Originally Posted by mike@x-ph.com

Try and log it to see if you are having any cylinder timing issues

I might try that but I am not super familar with how to on the JB4. I had a COBB before this and that was super simple. I will have to research the process. Any links you can provide?

More to the point though, should I be hearing knock at all? Again, I was under the impression that the DME is able to react very quickly to knock and correct it well before you would actually hear it.

[mike@x-ph.com]

Originally Posted by jwzimm

I might try that but I am not super familar with how to on the JB4. I had a COBB before this and that was super simple. I will have to research the process. Any links you can provide?

More to the point though, should I be hearing knock at all? Again, I was under the impression that the DME is able to react very quickly to knock and correct it well before you would actually hear it.

In normal conditions, you should not hear any knocks. Are you sure it is a knock not just injector noise?

[jwzimm]

Originally Posted by mike@x-ph.com

In normal conditions, you should not hear any knocks. Are you sure it is a knock not just injector noise?

It is inconsistent and pretty loud. I know what the injectors sound like and this is much more pronounced. I really do wonder if my knock sensor is bad and not picking things up.

I had issues with my COBB as well that scared me away from it. I had a pro-tune being done and was hearing pretty loud noises that sounded like knock. The pro-tuner swore up and down that it couldn't be knock due to the advanced control system in the car but I could not think of anything else it could be. I decided to chicken out and switch to the JB4 which is much less aggressive.

[Unklejoe]

Originally Posted by jwzimm

Hey all,
...but I heard what sounded like several aerosol cans being shaken.

That's not really how I would describe knock/pre-ignition. The kind of knock you think you're getting sounds more like a bunch of thumbtacks or corn kernels inside of a coffee can and it can be quite hard to actually hear sometimes (but I have heard it before on other cars!). It's usually described as more of a "pinging" sound. The frequency of a single knock event is probably around 7kHz depending on bore size. It's hard to describe but your description makes me think that it's something else that you are actually hearing. Also, if it is actually knocking that hard, you would probably feel a loss of power for two reasons:

1. The DME would be pulling a ton of timing
2. Engine power starts to fall off once you approach the knock threshold (but usually increases up until then). Once you're actually knocking, power starts to fall off even harder.

NOTE: Actual rod knock COULD sound like what you're describing, but detonation/pinging/pre-ignition usually won't.

Take this with a grain of salt, since the sound of something is pretty subjective.

Maybe grab a recording.