I have a 2002 5 speed it has a bad knocking in the engine what could it be at first it would knock when I first started the car and would go away now it continues and is louder

left front wheel speed sensor is more then likely due, to a malfunction sensor for the abs sensor, badly connected sensor, or wiring, or contacts corroded or damaged, the knock sensor is usualy do to a fault sensor at the crank shaft where the timing belt is due, this is also more then likely to your engine turnover problems and is just coincidence when refueiling

loud knock and for how long

is it a diesel or petrol

broken engine mount

loud tapping is tappets ..should go away once oil reaches top of motor
water pump or bearing something running off drive belts

if high milage engine
a loud knock at engine revolution or half revolution
big end bearings or
piston slap or gudgeon wear

Knock sensor rarely go bad. I have never changed one. If you start it and hear a knocking noise or the noise doesn't go away. That is your problem. Not the sensor.

The knock is likely a worn connecting rod bearing. Are you using the correct weight of oil, never use any heavier than 10W30W, heavy oil viscosity's cause slow circulation through the oil passages and starve the engine's bearings for oil.

Knocking can be caused by a bad bearing somewhere in the engine. When the engine is accelerated it might go away due to higher oil pressure.

When did you have the oil changed and how many miles does it have?

Is the knocking rapid (5 or 6 times a second) or periodic (1 or 2 times a second)?

Some knocking is due to low octane gasoline if you experience it at highway speed.

Good luck on solving this knocking problem.

While the engine is cold, remove the serpentine belt and start the engine and see if the knock goes away. If the knock goes away, then you might have a bad belt pulley. Good luck, Gary

it may need a lifter or valve adjustment when cold they will tick or knock depending on how loose or worn out then when it warms up they swell with heast and noise stops. after adjusting or replacing it will stop making noise

This could be at engine due to 1) poor gas octane 2) hot engine
for gas try super unleaded and test. keep an eye on temperature also which should be normal

Yes, this is usually loose pistons. Boring the engine and replacing pistons would fix it. But, this won't hurt anything and lots of vehicles do it. Unless it really bothers you, I wouldn't even fix it. As long as the knock goes away after the engine warms up a little. Do you have any other problems could lead you to a different solution? Like check engine light or low oil pressure when cold?

The job of the knock sensor is to detect the vibrations of engine "knock" caused by an advanced ignition system. It allows the fuel mixture to run extremely lean and efficient and when it can't perform at maximum effeciency, it "knocks" like it has bad gas and the computer gets the signal from the sensor and changes the ignition to ****** the spark and make the knock go away. If the computer is confused by the signal (too much signal, no signal or too frequent signal) the computer flips the light on with a 0402 code.

If you hit a pothole and the light goes on it might have got too much signal. If it starts going on at other times, you may have a sensor that is sending out too many signals and it might be from bad gas that the computer can't control the knocks.