False Knock Sources

[MustGoFaster]

Well here’s the deal. I have fake knock coming from somewhere. I can hammer it one time and have absolutely no “knock” detected, change nothing, hammer it again and be “knocking” up the wazoo. Some times I have had it knock in 1st and 2nd and then go away in 3rd. Changing boost (the one thing I can tune) has no effect, anywhere from 8psi to 18psi it behaves the same way. I was able to get it to “knock” for a split second multiple times just shifting into 4th at low rpm. I also get “knock” at part throttle some times, not in boost but almost. I also saw the some part throttle knock that corresponded to a hill, started at like 35 counts at the bottom and slowly tapered off as I reached the top. I have gone through and made sure everything is tight, tranny, motor mounts, t-case and the drivers side half shaft mount. Any other major components I should check? Other than that, anyone know of any common sources of fake knock? Don’t say the HLA‘s, they aren’t ticking. I am thinking it may be in the tranny or t-case, bad bearings or something? I just had the t-case recall done.

Car is a 92 GVR4 with some goodies.

[jd1828]

worn balance shaft bearings could cause it

[Matt D.]

I'd start at the source. Retorque the knock sensor, or try a different one.

[MustGoFaster]

Good thinking. :idea: I will have to give that a shot. As for the b-shafts idea, it's a fresh motor and the b-shafts have been "modified" if you know what I mean.

[Raptor]

From what you are describing, I would think your original assumption would be more accurate. It sounds like any load on the drivetrain is affecting it. Retorqueing the sensor is a good idea and you probably should, but that shouldn't be any different based on driveline load so I doubt that is the problem. Maybe your exhaust is hitting something slightly as it would change orientation when load was put on the motor boosting or not. Something along those lines would be my guess.

[LightningGSX]

I'd inspect the noise shielding on knock sensor, and make sure the shield is grounded.The voltages produced by the knock sensor are small, and can be easily shadowed by EMI.

[jd1828]

what is the torque on the sensor. maybe thats why im getting lot of knock also. i couldnt remember what it was when i put the new one on. i just know its not much more than hand tight. i think i did hand tight + 1half turn.

[Raptor]

I still think it is suspension load related, any issues with the knock sensor would more likely be affected during most of the general operation of the car as opposed to things like climbing a hill with little or no boost as he is describing. I still don't think retorquing the knock sensor and like Eric mentioned, checking the shielding is a bad idea, I just think it is less likely the problem by what he is describing.

[MustGoFaster]

Well after some inspecting and thinking, I may have found a source. Which way does the motor torque in the engine bay when going forward? The top (valve cover) towards the fire wall, or towards the radiator? I think it’s towards the fire wall, but I am not 100% sure.

Edit: When for a drive, still does it, I will have to keep looking.

[Pushit2.0]

You could try removing the knock sensor from the block, and zip tie it somewhere, then do a few pulls, if the car still knocks you know its somthing with the sensor. I could barrow you my wideband if you are worried about melting/destroying stuff.

~John