Spark Knock noise?

SouthArk370Z

Off the top of my head, I'd start with all the O2 sensors, MAF, fuel flow, ignition timing, and cam timing. I'm sure some of the other members can give you more ideas.

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TedB370z

I highlighted the times around when it happens....

Teds370zdatalog.zip

I had it log everything that the AutoGaugeX app could... (I have a Win8 phone...)

***This was from a parking lot, down a slight grade to a highway, regular driving on the highway, red light (when I pulled away is when the issue occurred) regular driving, then some spirited acceleration, then back onto the slight up grade, parking lot, then stopped and when I pulled in slowly it did it again, but very lightly.***

SouthArk370Z

It looks like the throttle plate isn't opening. "%Throttle" = 2 from 11:51:30 to 11:52:12. Ie, the ECU doesn't seem to be telling the engine to go faster. But, IIRC, the Throttle Position Sensor (TPS) that is reported via OBD has been massaged to account for VVEL. I'd try logging gas pedal position params (more than one) and see if it is sending the right signals.

And spark advance drops below zero. That sounds like anti-knock kicking in, which could cause the above. IAT and water temp aren't high enough to cause that much spark retard.

My wild guess is that it an anti-knock problem - the knock sensor(s) are too sensitive, something is rattling around and triggering the knock sensor, or you're actually getting knock for some reason.

But I'm definitely not an expert at this stuff, so take what I say with a grain of salt.

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TedB370z

The throttle position being at 2 was me just holding that pedal position/speed to keep the issue happening, hoping the log would show it, then I'd press the pedal more just to get it to stop.

I'm wondering if driving around with that cracked/bad catalytic converter on the passenger side damaged the knock sensor? or any other thoughts?

Just curious, where is the knock sensor? or do I not want to know...

SouthArk370Z

You need to give it some gas. A TPS of 2-3 is idle/zero-throttle. If you are giving it some gas, then I'd check the gas pedal electronics (you should be able to monitor it with your software).

Shouldn't have. Knock sensors are usually in the valley between the heads on a V engine (check the FSM for exact location on the Z) and would be "hidden" from any exhaust problems.

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TedB370z

I jacked up the rear of the car and turned off traction control to see if I could replicate the issue, but it wont do it, no matter how lightly I give it gas, so it seems not only must it be in gear but also under load...

TedB370z

I ended up taking the car to a Nissan Dealership. They had it for about an hour, they also did a 20+ min road test, and data logged, which the Head Tech did finally get it to replicate the problem. He even uploaded the data to another tech at Nissan, after everything, going over AFRs, every sensor, mechanical etc, its completely normal, and there's nothing wrong with my car. Every sensor was/is reading fine and there's nothing mechanical setting off the knock sensor.

Apparently it does say in our manuals spark knock under light acceleration OR uphill is completely normal. The tech said I hear it a lot louder do to the open-element intakes. I explained I've just never heard of a $40,000+ sports car doing that, but he said it's only under light acceleration or uphill to increase fuel efficiency.