[rhenier99]

Hi everyone, I was hoping someone with a bit more knowledge could explain to me if there is a problem with these photos? I'm getting drivetrain faults constantly due to knocking detected on cylinder 1 and 2 (fault code 168002: Knock sensor 1; engine noise below limit value or line interruption)

I took off the charge pipe and throttle body to take a look at the knock sensor, I cleaned up the connections and put it back, didn't seem to have an issue. I then took the intake manifold off and took an endoscope to take some pictures of the intake valves to inspect the carbon buildup, I've attached them. The debris was stupidity from my side not properly cleaning the intake manifold before removing it, it was insanely dirty (I only recently bought the car) but I've since cleaned the intake valves from the debris. How bad is the buildup there, could it cause issues as far as knocking? I'll admit some of them look quite bad.

I then took off the coils and plugs and put the endoscope in the sparkplug gap, their photos are also attached, I've named them appropriately. Note the buildup on cylinder 3 and 2. Please also ignore the debris in cylinder 4, I've since vacuumed it out. Cylinder 1 and 4 look quite clean (ignoring the debris in 4) I think, but 2 and 3 seem to have a lot of carbon buildup and even look to have unburned fuel or some sort of substance that is still wet? Does anyone know the extent of this issue?

So my question is... can anything seen in the photos be causing my drivetrain fault, and if so what can I do to fix it? Walnut blast? Injector replacement? Is the knock sensor faulty?

Thank you.

[Ak1221]

Any update

[sspade]

You never told us how many kilometers on the engine.

What octane fuel have you been running... and what is your oil change interval?

[rhenier99]

I think I posted this in the wrong section. I cleaned everything up and put it back together, I cleaned the intake valves and they look quite good now not a lot of carbon buildup on them.

The car has 195000 kms, it's had a new oil pump chain put it and new guides on the timing chain, but I have not replaced the timing chain myself, whether or not the previous owner(s) have I'm not sure, but according to my indy and my judgement the chain is still fine, but will need to be done soon, especially now that I'm getting this issue I'm considering doing it as it may be the cause.

The cause of the drivetrain is the knock sensor code, I've had the sensor replaced with a brand new BMW one so that rules the sensor out. That leaves possible wiring issues (judging by the voltage it seems the wiring is picking up noise that it shouldn't)
or an actual mechanical fault (timing chain)... I'd just assume that if the timing chain was so out it would cause more than just a knock sensor code, and it's always knock sensor 1, never ever knock sensor 2.

To answer your question, I always use the best quality fuel as well as oil, 95 octane, there are differences in stations I'm sure but I'm mostly using the same one my brother did who has the same car and never had issues.

I've only had the car for about 2000 kms but I did an engine flush with oil and filter replaced twice (which was also done prior to me getting the car). I plan on changing oil every 5000 - 6000 kms

The car doesn't feel sluggish at all, it drives very well and doesn't seem like it's lost any power (which leads me to believe it's not mechanical). Unfortunately as soon as I have a bit of fun the error pops up. (the knock sensor voltage stays constant, but the preconditions for the fault coming up are RPM and engine temperature based, so it pops up quicker if the RPM is higher).

I'm at a loss and have spent way too much money chasing this fault. HPFP replaced, new injectors, sparkplugs, coils. I'm taking it in again when I have spare cash and will update this with what they find.

[rhenier99]

It ended up being a stripped wire, even after i had an auto electrician tell me the wiring is "good" and spent A LOT on mechanical parts. Took the whole harness out myself and saw a break in the wiring leading to and from the knock sensor and the DME (specifically 12517619135 the harness for sensor module 1 that plugs into the DME) I guess sometimes you just have to DIY. After I found the break I had a different, much better auto electrician fix the harness up nicely and plugged it back in, no issues now, finally.