MatthewsMaxima

Yeah, I read several threads already with people arguing about which is better, which is required, better/worse gas mileage, increased/decreased performance, blah(3)

The dealer told me that I need to put premium in the Maxima...the manual states it, so I'm gonna do it. I dont think they're getting extra money from oil companies to tell owners to use premium gas....to my point.

I'm getting the slightest, lightest sound of a diesel engine sounding knock while at a redlight or with it running in park. If you're not looking for it, you wont hear it. Is this normal? I'm prob being paranoid with all the sounds and smells I'm sensing because I have new car paranoia n all. Car guy I know says it sounds fine to him and that possibly the previous owner used regular gas and that might be causing the ever so minor knock. He said to run a bottle of Chevron Techron concentrate through it and only use top tier gas..and premium of course. This should help.

Any thoughts? Experience in this?

chrome91

iTrader: (1)

if you have the diesel or pinging sound its probably got less than 91 octane in it, you need to put some octane booster in the fuel tank. pump gas already has additives and detergents, you dont need store bought additives. you do need to use 91 or higher octane in it though, its stated in the manual that it needs 91+ for a reason

87 or 89 octane youre getting pre-det from the low octane, keep doing it under heavy conditions and youre gonna get holes in your pistons

dexcool

Check into some of the "main bearing issues" threads here, MAYBE, thats what your hearing. Keyword, MAYBE. Just a thought bc you said its soooooo slight that you wouldnt hear it if u werent listening for it...

CorollaULEV

Dude...you ARE NOT hearing pinging at idle. Knocking or pinging or (more correctly) auto-ignition happens when the spark plug fires and the extreme pressure in the cylinder cause a massive, uncontrolled auto-ignition of the fuel. Octane simply cause fuel to burn slightly slower and have a more predictable flame propagation. Spark plug ignites a flame kernel, which very smoothly and predictably propagates outward (increasing cylinder pressure smoothly and pushing piston down on power stroke). Lower octane fuels will spontaneously ignite under extremely high pressure (pinging). Higher octane fuels are more resistant to this. Meaning once the flame kernel starts propagating and cylinder pressures start increasing, the fuel will auto-ignite spontaneously. You develop multiple sites of ignition in the fuel/air charge and an immediate spike in cylinder pressure (real bad for wrist pins, rings and conrod bearings).

Point is that you have to have a highly pressurized cylinder for this to happen. Cylinder pressures are NOT high at idle with no load on the engine. Pinging/knocking/detonation/auto-ignition happen at high load and is much worse at low rpm (on take-off).

Not only that, but these engines have a knock sensor. That little microphone will tell the ECM to back off on the timing. If it knocks, it will probably never get bad enough to even hear because the ECM's ear is a lot more sensitive than yours. The ECM would retard timing and you would never even know it knocked.

Look at main bearing.

Thanks,
Travis

zillafreak

You sure it isn't the injectors you here or possible valvetrain?

RCM78

How many miles on the engine? Could be a failing timing chain tensioner.

ThinBlue82

iTrader: (1)

Well I learned something new today. Thanks for that nugget of information Travis!

OP- just turn you stereo up and forget about it!

MatthewsMaxima

Yeah, I read about 7-8 pages of the Buyer Beware thread dealing with the #1 bearing and people either having to have the bearing replaced, or new short block. I watched the videos posted with the sound of the engine, and mine doesn't sound anything like that, but it doesn't sound terribly smooth either. Its a 2011 previous lease with 36K, certified used with powertrain warranty, extended warranty and service warranty. If it gets any louder, I'll just take it to the dealership in Athens, GA.

Thanks for the info, Dude(s)

BlackKnight11

Ill just post this question here, what is the intermittent knock and ticking sound i hear right after I turn my car off???? It does it for about 3-5 minutes after I park and turn the car off.

Daaavid

Radiator fan and the variation of metal parts contracting at different rates causing that ticking noise. Nothing to worry about.

BlackKnight11

Thank you Dave!