Spark Knock noise?
 

09, Touring, 7AT with 61,000 miles....I got gas today, and immediately had a CEL. Got back to the office, and it was a P0300, cleared, has not come back in the 20 miles I've driven so far... but Its making an odd sound... exactly like the one in the sound clip from this post...

http://www.the370z.com/engine-drivet...ml#post2541785

I mean exactly, but a lot more audible, just not all the time, just from a slow gradual start. Is this from crap gas? I've always put in 93, but I'm not sure what else could be causing it.

First thing that comes to mind is the flex plate for the torque convertor is cracked. Hopefully it ain't that.

or its a bad batch of gas being that your notheren could be water what with the cooler weather and all try a couple bottles of heet and burn the gas down some to see if it goes away.

P0300 is a Cylinder Misfire Detected Random Cylinders error. By itself, doesn't mean much.

How immediate is "immediately"? As soon as you started the engine? If so, then it may not be the gas as the new gas takes a while to make it from the tank to the engine.

The easy things to check are:
* Battery condition - a weak battery can cause problems, especially with modern, computer-controlled engines.
* Water/dirt in fuel - try some fuel system cleaner with methanol to clear the water. May need to change fuel filter.

Not so easy:
* Dirty TBs - after 61k miles, they probably need a good cleaning. DIYs on this site. If you decide to clean the TBs, go ahead and clean the MAFs while you are there.

I bought the car at 47,000 and took apart the intakes and cleaned the TBs and the MAFS, just to be sure there was no oil buildup on the MAFs since the previous owner had installed K&N Typhoons.

Immediately as within a few minutes, which is what led me to believe it was just the gas....

but another issue is, only around 1000 rpm, I hear a rattle, I took off the strut tower brace, all the plastics, looked around with a flashlight, cannot find what or where its coming from, it almost sounds like a pipe hitting off something metal... its not valve tap or the spark knock noise, and its not rhythmic enough that it goes exactly with the engine speed, hopefully this isn't the flex plate. Is there a plate you can remove to inspect the flexplate? or is dropping the transmission the only way? Thanks.

I added a bottle of octane booster and filled it up with 93 at a BP, there was half a tank of the Sheetz 93, so hopefully filling it up dilutes the crap gas.

I'd have just syphoned it out, but its about 15 degrees here and no where to put 10 gallons of gas.

I love sheetz but at the same time hate them, I avoid putting their gas in my Z, I know locally many of the stations use the same fill plant(there is a gulf fill station in delmont and altoona) but I do not think sheetz uses them, my friends and I have all experience less mpg and some minor issues time to time with sheetz gas, I put it in my civic but not in my Z, all the other stations around my area seem to use that gulf fill station.

I would also run a can of seafoam through it then change the plugs...

What about the fuel pump? SouthArk370Z you brought up the fuel filter, but I know they are all-in-one units where the fuel filter/pump/sending unit/level sensor is one contraption, is it worth pulling out to clean?

The filter is just a possibility. I'd have to be pretty sure it was the filter before I would go to the trouble of pulling the pump.

Here's the rattle noise coming from under the car at low RPM, between 800 - 1200 RPM.... sounds like it might be the flex plate..

http://youtu.be/M0RsMaWbCqQ

UPDATE: jacked up the car, took off the preview plate on the transmission. Flex Plate is fine, honestly looks brand new..., started/stopped the engine to rotate it the who's way around and not a single crack...

If your are ever in the greensburg area and cannot get this figured out I can have one of my techs take a look at it for you. I also have some connections to Cochran( I work with their former Service Manager) and West and East Nissan dealers if you get to that point, let me know.

Thanks JoePro, I'm taking it to my local mechanic Tuesday but if he isn't successful I'll let you know.

I did end up taking out the fuel pump, its fairly simple. I used this how-to on upgrading the fuel pump for instruction on how to disassemble the fuel pump/filter/level sensor:

CJM Tech Site: A First Look: The 370z Fuel Pump Assembly

It was pretty funky, before pics of it disassembled, there was flakes and chunks of sewt, and the actual fuel filter wassaturated with more sewt, turned the water black when I cleaned it:

Attachment 83397

Attachment 83398

After everything was cleaned, ran biodegradable degreaser and warm soapy water through the fuel pump (using a 9 volt battery and the green and black wires on the pump itself), then plain clean water, then used an air compressor and let it sit to dry everything out

Attachment 83399

Attachment 83400

Its not a difficult unit to disassemble, just have to be patient, and I'm clueless as to why Nissan says it's not serviceable, and doesn't sell the fuel filters separate?

Mechanic said the rattle is coming from the passenger side cat - and other than one time they could not replicate the spark knock. The odd thing is it will only spark knock/diesel when in gear it can idle perfect and goes through the RPM range fine when in park or neutral. If it's in gear say at a stop light... if you press the gas slowly it'll hesitate and you'll hear the dieseling noise. It will also drop RPMs to 500 randomly when stopped in gear.... thoughts? If it was an issue with the cat I'd assume it would have the issue regardless of being in gear or not?