* Fuel injector problems: A faulty fuel injector can cause the engine to idle irregularly by delivering too much or too little fuel to the cylinder. This can cause the engine to run rich or lean, respectively.
* Spark plug problems: A worn or damaged spark plug can cause the engine to idle irregularly by not providing the correct spark to the cylinder. This can cause the engine to misfire, which can make the engine run rough.
* Compression problems: Low compression in one or more cylinders can cause the engine to idle irregularly. This can be caused by a variety of factors, such as worn piston rings, a damaged cylinder head gasket, or a cracked cylinder.
* Clogged catalytic converter: A clogged catalytic converter can cause the engine to idle irregularly by restricting the flow of exhaust gas from the engine. This can cause the engine to run rich, which can make the engine run rough.
