Does your car or bike engine knocks and does not idle at constant rate? This is a common problem with petrol engines and mostly people think it related to bad fuel or some dirt in the carburetor or injector in case of MPFI. Adding some kind of anti knocks additives to the petrol will reduce this for a while but it’s like taking painkiller tablet and not knowing the root cause of pain. Here I will tell you a simple DIY by which you can check and most probably fix the knocking the irregular idling problem of your car or bike.
First step will be to remove the spark plug caps (if there are several like in case of car, put a mark so that you know which one goes where when you refit them) and using the plug removing tool, remove each spark plugs one by one. Just like screws you need to unscrew plugs in anti-clockwise direction. You may plug the hole with cloth pieces so that you don’t accidently drop anything inside that hole.
Now when you have the plugs in your hand, clean them with an old toothbrush using paint thinner. If you don’t have paint thinner then you can also use petrol. Please wear latex gloves and goggles while doing this. Do not use sand paper or any other thing to clean plugs which can increase the plug gap.
After you have cleaned the plugs and they are completely dry we need to check these using a digital multimeter. We are using a simple multimeter which cost very less and often found in homes. Set the multimeter to “diode” mode and touch the probes (any, no polarity issue here) to the points marked with green color arrow in the picture. If the plug is healthy, you should see a reading close to 0 that is no more than 1 or 2. If the reading is very high or worst there is no reading at all then you need to buy a new plug. Similarly check all the plugs. Change the bad plugs with new ones. If you are able to pull out the plug cables from other end also you will have two ends of the plug cable which you can also check using the multimeter in similar way. Here reading can be any number from 0 to 15. If you are getting reading that is more than 15 then it means cable is worn out. Replace the cable with new one. Usually we replace the full set and not just one. Once you have done this I am sure you will find knocking problem and many other problems like late start and irregular idling gone.