spark knock

I have a 96 camry with 120k on it. I have owned it for 4 months and the spark knock has steadily been getting worse. At the start I put in higher octane fuel and it solved it. But then it got bad even with the high octane fuel so I had it tuned up. It's mostly gone but still has spark knock while gently accelerating. The mechanic said he would back off the timing a bit. Will this really solve the problem? Should I need to run the highest octane fuel? Thanks

What engine and transmission?

Your owner's manual will tell you what gasoline you should be able to use without pinging. Are you getting a "Check Engine" light on the dashboard?

I had this problem with my 4cyl 2000 Camry. It would only run well on premium, and had poor performance when using regular. The manual calls for regular in this engine. Backing off the timing will substantially reduce performance.

I used a carbon cleaner (SeaFoam) to clean the compression chambers of carbon. And, I used Techtron in the gas tank to clean the injectors and fuel system. SeaFoam can be bought at your auto parts store. GM also makes a good top engine cleaner.

This site describes how to do it. (It's for a Honda, but the procedure is the same)
http://www.superhonda.com/tech/carbon_cleaner_treatment_how-to.html

or here
http://64.233.161.104/search?q=cache:CE0q-bXY40gJ:www.motorminute.com/Service/CarbonRemoval.pdf+&hl=en

This procedure really helped my car. The engine runs like a top now-- on regular.

Oh, I should mention... Be prepared for a lot of fumes and white smoke to come out of your tailpipe during this procedure. Even after you're done, and you're burning out all the carbon (blue smoke), expect to get funny looks as you dirve around for a few miles with smoke billowing out from behind you. I actually thought I'd ruined my engine--for a few moments there. But, once the carbon is burned out the smoking stops.

Just a warning.

Yes, carbon cleaning may be the answer. Probably won't hurt anything. The question still remains, is the "Check Engine" light on? If so, first fix whatever is that problem.

What engine and transmission?

Your owner's manual will tell you what gasoline you should be able to use without pinging. Are you getting a "Check Engine" light on the dashboard?

I have the 4 cyl with auto trans. I know the manual says you should use regular. I just had a basic tune up done and the pinging lessing quite a bit. Before the tune up when I used regular unleaded I would get the check engine light on but it would go away when I used premium! But now I just put reg in again, after the tune up, and no light yet. I'm just really picky about any abmornal sounds coming from my engine. Thanks for your reply!

You're welcome