97 rattle under load

I have a 97 and it runs great. When I had 4 people and a bunch of gear going up hills there is a knock coming from the engine. With out anyone in the vehicle climbing hills has a very slight knock. I also here the knock when towing a boat. There is no knock sensor on the 97 right so what can I do?

My 97 does the same thing.I have used various cleaning products (Sea Foam,BG44, Lucas) with minimal improvement. The only solution I have found is running 89 or 93 octane. The knocking is minimal and with gas now over $ 3.25 for 93 I run 87 .

Thanks that was what I was thinking but hoped maybe someone had found a cure.

You might take a multimeter on the ohm scale and an external infrared temperature sensor and check the resistance calibration of the IAC, CTS (intake air and coolant temperature sensors) at various temperatures and see if they have not drifted with age. Also if the Map sensor is off a little bit (need a good vacuum gauge) testing voltage readings at various vacuum readings, they can all affect the computers igniton timing and cause knocking. Lastly if your engine is running a little bit too hot, under heavy load it cause pre ignition (knocking).

Some injector cleaner might help a little bit for a while too.