Detonation..

[touringcamry]

I was driving around a few days ago and I started hearing rapid clicking noise coming from the engine area whenever I pressed the gas. It did not seem to matter what gear I was in.

I was doing about 35 MPH in 4th (approx 1700 RPM) on a flat road. Later I tried 25 MPH in 3rd (approx 1700 RPM) and 2nd (approx 2500 RPM) on a flat an uphill road and had the same thing happen. Normally, I can go up that hill at 25 MPH in 3rd without any issues.

The temperature gauge looked normal so I am thinking it was not induced by overheating.

I did not just fill up the gas tank at that time. The fuel gauge was at about 2/5 at that time. That clicking noise just suddenly started at that time. I went to a 76 gas station and put in about 5 gallons of 89 to help prevent detonation, I normally fill 87, and the noise went away and has not returned. I have filled the tank with 87 and still no issue today.

WTF happened? Could I have had some bad gas? If yes, why would it suddenly start after burning 3/5 the tank from that fill and then suddenly go away. I guess the 89 could have helped prevent the detonation...but it was 5 gal diluted in maybe 5 to 7 gal of 87.

The ambient temperature was in the mid 60s and I was driving around in an urban area (light traffic on city streets) in Indio.

[Mistabullet]

If a higher octane cured the problem then it was an issue with the gasoline.

As for why the problem randomly started, it could have been bad fuel that was diluted with good fuel up until a certain point.
What I mean is, perhaps higher octane fuel is denser/heavier and resides at the bottom of the tank near the pump. Once that higher octane fuel was used up all that was left was the lower octane fuel which caused the knocking.

Of course, this is just speculation and I could very well be talking out of my ass .

[JAKSTER]

Are you able to pull the spark plugs if the engine was detonating you may see small bumps on the center porcelin at the end of the plug where the spark comes from. The pin size bumps show that the plug has gotten hot maybe from the engine getting lean. That may be a computer glitch. The tip shoud be a nice light brown to dark tan. If it is as I described white with specks get it to the shop for a computer check.
No one changed your plugs did they? make sure you have the DENSO plugs and not NGK. NGK is made by Denso but is not quite the same. Autolite is also made by Denso but DENSO has a seal on the porcelin and is a cleaner burning plug. The bumps sometime indicate detonation and running to lean. Do you have a K&N filter or any other engine Mod's the K&N will lean the engine due to more air flow. It is something that will cause the ping. So will bad gas. If the station just filled the tanks from a truck the fuel can be mixed up with allot of water that is in all storage tanks. That fuel is crap or if the tank is very low you could be getting some poor fuel off the bottom.

[touringcamry]

Everything engine related is from the factory aside from the oil and oil filter. The car only had about 9800 miles on it at the time. I still haven't been able to reproduce the problem.

I will check the spark plugs shortly.