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ive read on some threads about pingin and knocking, but i dont really know wat that is. Can somebody please clarify that for me? thanks...and also, i have 2002 pathfinder and it sounds like a lawnmower all of a sudden. its not losing power, but it sounds as if there is like a leak in the muffler. we took it to the dealer and he said that they checked it out and its all fine. he said that next time we bring it in, do a tune up and it should be fine (it has 30,000 miles) has nebody had a similar problem like im having? it almost sounds as if there is a leak in the exahust, like from the middle of the car. it sounds louder and like a lawnmower or somethin...
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Premature detonation

Some causes are carbon build up within the combustion camber causing a higher compression in which the gas air mixture combust before it was intended to.
And timing being off.

This results in pistons ‘knocking pinging’. Higher octane gas allows for more compression before detonation occurs.

What I know anyway
 

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There are two things that could happen. One is pre-ignition the other is detonation. Pre-ignition is just as the name implie, the spark in the cyclinder occurs before it should. This can occur due to hot spots in the cyclinder. Detonation is a rapid uncontrolled burning of the fuel. Detonation is what can do damage to an engine as the burn process slams the piston.

With higher octane the fuel burns more slowly and more controlled. Thereby allowing more of a burn more power and more fuel being evenly burned allowing for better efficieincy.

In either case it is rare in a modern car due to the electronics that monitor and adjust various factors in the engine.

"I think"
 
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