Toyota Repair: ENGINE KNOCKS&PINGS, toyota celica, combustion chamber

Question
1991 TOYOTA CELICA GREAT CAR WITH 236K MILES. I HAVE DEVELOPED ENGINE KNOCKS & PINGS. I PUT IN SUPER UNLEADED AND IT SEEMS TO GET A LITTLE BETTER BUT IT IS STILL THERE. I DRIVE 42 MILES TO AND FROM WORK IN NON STOP HIGHWAY TRAFFIC AND IT RUNS GREAT. IT IS WHEN I EXIT THE HIGHWAY THE SOUND IS HEARD. I ALSO PUT IN FUEL INJECTOR AND IT DOES NOT SEEM TO WORK. IF I PUT REGULAR UNLEADED GAS IT KNOCKS&PINGE CONTINUOUSLY. ANY SUGGESTIONS. THANKS, MIKE

Answer
Has the engine timing been checked, it sounds like the timing may be too far advanced, check it with a timing light, the diagnostic connector under the hood should be jumped between terminals TE1 and E1 while checking the timing. This could also be caused by higher than normal combustion chamber temperatures so make sure the engine is not overheating and the check engine light is not on.