Why does my clio Knock when turn off?

Answer 1

There are several causes for run-on or dieseling: The engine can be overheated; it can have carbon buildup in the combustion chambers; you could have the wrong spark plugs installed; the throttle positioning solenoid (TPS) is stuck; or the carburetor needs cleaned and adjusted. To begin, first check the TPS (if your model is equipped with one). This takes two people. Take the air cleaner ducting off the carburetor so you can observe the throttle linkage. With the ignition switch in the run position but the engine NOT RUNNING: 1) Push the accelerator pedal down about half-way. (Don't pump the accelerator.) 2) Release the accelerator. 3) Turn the ignition switch off. You should hear a click and observe the throttle linkage move to fully closed. If not, replace the TPS. The next things to do are: flush your cooling system with an aluminum-safe flush, re-fill with a 50/50 mix of coolant and water, change your spark plugs, shoot some carburetor cleaner into and around the carburetor and see if the symptoms go away. See if the air filter is damp with fuel. A dirty air filter can cause a rich fuel-air mixture and in extreme cases it can cause fuel to blow out of the carburetor and soak the air filter. This can lead to dieseling. In any case, if the air filter is more than 50K kilometers old, it needs to be replaced...sooner in dusty conditions. If your spark plugs are caked with carbon, the rest of the combustion chamber probably looks just as bad. De-carbonizing the combustion chambers means pulling the head although some people have reported success by squirting a few cc's of clean water into the carburetor throat while the engine is running. Supposedly, the steam loosens the carbon. It might work for a while but it doesn't cure the cause which is probably either leaking valve seals allowing oil to drain into the combustion chamber or an excessively rich fuel-air mix. The only ways you are going to have dieseling in a Clio built after 1992 (fuel injected) would be if: 1) The crankcase is filling with blow-by gases. 2) The fuel pump relay is somehow stuck "on". In this case, you will hear the fuel pump running. This is not very likely but it is cheap to replace. If the fuel pump relay is good, that would indicate you need to re-build the engine because the rings are worn. Check compression in each cylinder, dry and wet (about 20 cc of oil will temporarily seal the leaking rings) before you proceed with an engine rebuild. The wet and dry readings should not differ by more than 5% to 10%.