So my 02 Escalade lq9 engine has started to run horrible, no matter what gas grade i put in it when its hot i get bad preignition detonation, I put Union 76 91 octane in the truck and it ran ok but when its hot outside like above 90 or around there I get bad detonation at low rpm, like going up a hill yesterday it was knocking and I could hear it in the cab. If i gave it more throttle and brought the RPM's up it goes away. I do not have any check engine lights or codes, my first though was knock sensors but i do not have a code saying they are bad. Any places I should look? it does have 200k on it and I thought about changing the spark plugs and wires to see if that helps.
Also in the past month my engine cooling fan has become very loud. The engine temp stays right where it is supposed to be at operating temp, is this a sign my fan clutch is going bad?
Also in the past month my engine cooling fan has become very loud. The engine temp stays right where it is supposed to be at operating temp, is this a sign my fan clutch is going bad?
