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Question DetailsAsked on 1/22/2018

71603 What could be causing a knocking noise in my engine

I have a 2004 Nissan Sentra standard transmission and it will not run, there is a knocking and really loud noise in the engine.

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1 Answer


Could be any of a dozen or more things - but an engine making a loud knocking noise should not be driven (even to the repair shop) until it is fixed - could end up destroying the engine. Common causes in no particular order though first is most likely (ignoring the automatic transmission causes for your case). These are just ones that can cause the noise without the car rolling - if happens ONLY when rolling then not an engine problem, is a ddrive train or wheel area issue. - low or excessively old dirty engine oil causing internal wear and poor lubrication - timing belt/chain jumped and pistons are hitting valves (if interference valve engine) - slapping piston because of a worn cylinder or broken piston rings - pre ignition (a cylinder firing before it should) due to a hot spot in a cylinder - post-ignition (unburned gas exploding in the exhaust system) because of a spark plug which is not firing (due to shot plug or wiring problem or if a coil-on-plug design, a coil going out, or valve problem - if only when warmed up, low coolant causing preignition because engine is overheating - bearings worn out - crankshaft, piston connecting rod, or piston wrist pin - broken valve sticking into cylinder and being hit by a piston - stuck hydraulic lifter making for noisy valve operation - bearing gone bad in power steering pump, alternator, water pump, oil pump, etc - fan hitting something - debris (or animal) in engine compartment or something hit it and bent a blade which is now hitting something - clutch failure (several things in clutch can cause that type noise) - if only or predominately when turning wheel (even when sitting still), low steering pump fluid or shot power steeering pump or broken part in the steering gear - timing sensor shot (with electronic canshaft sensor controlled ignition/injection) so the engine fuel injection/ignition timing is off - transmission problem like bad input or midstream bearings or broken synchronizer

Answered 2 years ago by LCD

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