Celica Knock sensor error
I have the same Toyota Celica as you from 1997 7A-FE engine with 250.000km (155.000miles aprox). I got a knock sensor error a long time ago (code 52) and I replaced the sensor but I still got the error, let me explain.
It usually happens around 2000 - 3000 rpms when the engine is under load going uphill for example or when I have the gas pedal at a certain position and then I step on it a bit more when the check engine light comes on and I get this code. When going on high rpms this doesn't happen. The car doesn't seem to make anything weird or work badly is just the light turning on, i don't know if I'm losing power when this happens but I don't notice a big difference.
I've checked injectors, changed to higher octane fuel, used several inyectors and carbon build up cleaning products, checked the throttle position sensor and nothing seems to help. Also deleted the error code but it comes up again anyways.
I'm desperate and would be so thankful if you could help since no mechanic can tell me what's wrong neither the shops I've taken it to.
Thanks for all your videos I really enjoy and learn from them, greetings from Spain.
Your car has a timing belt and a non-interference engine. If it's knocking as you say, the ignition timing could be off because of a stretched belt. Has that been replaced too? If you have access to a live data scanner, I'd check to see what the ignition timing is compared to specifications.
Check wiring between the knock sensor and the ECU. If it's a 1997 American market model it will have an OBD2 port and it should be possible to read data using a standard scanner though of course there will be a limited amount available on a car that old. It may still provide important clues as to what is going on. Even an inexpensive scan tool these days is capable of reading live data.
Why was it running low on oil? Was it burning it or leaking it?
The timing belt has 16000 miles which I think it's ok, unfortunately I don't have a live data scanner and I don't even know if you can plug one in the car since it doesn't have an OBD port.
The first time the check engine light came on i noticed the engine was running low on oil, not too low but right at the lower limit, but I never got the oil pressure light on. I don't hear a knocking sound from the outside in case something has worn out since knocking sounds usually get louder as you rev the engine and when I rev the engine I don't get the check engine light on, only in mid/low range of rpms.