I have a really loud "knocking" sound upon start up. This sound is only when starting the car up. As the car warms up, or is warmed up by driving, the sound goes away. I did a search on this topic prior to this post, but I was wondering if it was due to the octane of the gas. I've used Chevron's lowest grade for quite awhile since gas prices are rediculous. The price for premium gas is well over 2 dollars a gallon. I know that we're suppossed to use the highest octane and was doing so before prices became high. It happened once at the beginning of March, and once at the end of March. No indicator lights come on, but when the car was taken to a dealer, they didn't know what the problem was. I was told to check the oil, but the oil is fine. Also, if this is a case of detonation, do you think that it has already damaged the engine?

 

premium gas is .20$ more per gallon than the lowest grade (87)...20 cents x 18.5 gallons (assuming you have left your tank bone dry) comes out to $3.70 extra per tank...figure you fill up every week...i doubt you fill up that much, but just for this model, lets say you do...$3.70 x 52 = $192.40 per year...that is if you fill up once a week which is a lot...you have a gle which means you paid at least $26k (after negotiations)...if you pay that much on a car, $192.40 extra per year is not digging too deep...i am a full time student and only work part time and it doesn't dig too deep for me...

so what if the prices are over $2.00...i don't understand how you are rebelling by hurting your car...just put premium in from now on...the only time you should use regular is if you are empty on gas and the only gas station around either only carries regular or you don't have enough for premium...1 tank of regular every once in a great while shouldn't hurt it, but what you are doing will...just give it a test...go through a full tank of 92 (let it flow through) and then the next time you fill up with 92, if the knocking sound isn't gone, go back to the dealer...but if you keep using 87, it will most likely keep happening...sorry if i'm coming off as a little rude, but treat your car nice and it will treat you nice

 

Thanks...that's what I figured it was too. It sucks living out in the middle of "paradise" though...everything is so expensive and our economy sucks too....was in a recession. I'll try that out and see how it goes!

 

is your gas tank 18.5 gallons? im asking cuz my tank is about 13.5 gallons, and im a bit confused.

thanks

 

All maximas have and 18.5 gallon gas tank. When the fuel needle reaches 'E', there are still like 2 or 3 gallons left in there.

 

well when i reach empty, and i fill up... it takes about 13.5 gallons every time to fill up. I also thought that's what it said in the manual (13.5). Well, I guess I'll check again when i get off work.

 

I experienced this some time ago. I am using the same brand and octane level gas today as I was then.

I had let the car sit for close to 24 hours, then started the car and moved it about 20 feet. Later, I started the car again to leave and I heard the loud knocking. Not pinging, it was definetly knocking as if the motor had broken. The noise subsided after 20 seconds or so.

It has not happened again. Another member reported similar activity with loud knocking at startup.

 

That's how mine is too. It lasts for about 20-30 seconds. I'm crossing my fingers and hoping that it won't occur again too.

 

Just to clear things up for people......

knocking, pinging, detonating: Sounds like marbles banging against the inside of a metal can while you're shaking it up and down... caused by premature combustion.

knocking, banging, rattling: metal piece hitting another metal piece in your car.


You are experiencing the 2nd one, right? If you are experiencing #1 and the knocking doesn't stop until your car warms up... you would be driving a new car right about now.

 

you have to up the octane...