2000 altima pinging

My 2000 Altima has 93000 miles on it and recently after taking it on a trip to Salt Lake City and fueling it with thier normal gasoline of a 85 octane rating a few times, i have returned to Phoenix and have noticed a pinging everytime i shut off my engine. I have heard before that this is due to the lower octane fuel, but i have added 2 new tanks of 92 octane since this began with no improvement. Does anyone have any ideas?

Pinging is related to compression ratio and octane rating of fuel. Pinging happens under load primarily to cars built before mid 80s. What you are describing is called "engine run on", which was also a very common issue with 70s-80s vehicles. Knock sensors and computer controlls pretty much eliminate pinging. When the key is turned off on a fuel injected engine, the injectors stop the fuel. Your car must have a problem with one or more injectors that allow fuel to leak all the time. Run on can only occur if there is fuel in the combustion chamber. There isn't any fuel or additive that will fix leaking injectors or eliminate the engine continueing to run after shutting it off.

Great!!! So how much is a new injector going to cost me? Is that something i could put in myself?

Nice description JustSayGo.

Now before you go out and buy injectors, try verifying if you indeed have leaky fuel injectors. You can do that by simply lifting the fuel rail, with all injectors attached, and putting the igntion key to ON (not START) position. If there is indeed a leak you should see some fuel dripping somewhere from the injector(s). Beats having to replace them all.

Also, a bad fuel pressure regulator can leak additional raw fuel into the intake vacuum hose or run the injectors under higher-than-normal pressure.

kblk1822 removing and replacing injectors is not difficult or a terribly involved task. If you think you can do it, I don't believe you will have a problem. Look for a repair manual at Rockauto.com. You can check injector prices at Rockauto and AutoZone. The most important thing would be to inspect for fuel leaks after you finish putting the injectors back in place. The procedure that jserrano wrote of is the next step. If you decide to take your car to a repair shop, I recomend Kenny Burns, my personal friend and owner of KB TRANSMISSIONS 3130 E. Main Street #8 Mesa, AZ 85213 (480) 854-7615

If i were to take these injectors out, is there any sort of gasket that would need to be replaced or is it simple a few screws and they will pop out together? And another thing, is it possible to hear the pinging while the engine is running? would that be the same problem or something different?