Starter motor noisy or excessively rough in engagement
* Starter pinion or flywheel ring gear teeth loose or broken
* Starter motor mounting bolts loose or missing
* Starter motor internal components worn or damaged

Engine starts but stops immediately
* Insufficient fuel reaching the fuel system
* Loose or faulty electrical connections in the ignition circuit
* Vacuum leak at the carburettor/throttle housing or inlet manifold
* Blocked carburettor jet(s) or internal passages
* Fuel injection system faulty

Engine idles erratically
* Incorrectly adjusted idle speed and/or mixture settings
* Air filter element clogged
* Vacuum leak at the carburettor, inlet manifold or associated hoses - carburettor models
* Vacuum leak at the throttle housing, surge tank, inlet manifold or associated hoses - fuel injected models
* Worn, faulty or incorrectly gapped spark plugs
* Incorrectly adjusted valve clearances - B6 and E Series engines
* Faulty HLA Adjuster(s) - B3 and B5 engines
* Uneven or low cylinder compressions
* Camshaft lobes worn
* Timing belt/chain incorrectly tensioned

Engine misfires at idle speed
* Worn, faulty or incorrectly gapped spark plugs
* Faulty spark plug HT leads
* Incorrectly adjusted idle mixture settings
* Incorrect ignition timing
* Vacuum leak at the carburettor, inlet manifold or associated hoses - carburettor models
* Vacuum leak at the throttle housing, surge tank, inlet manifold or associated hoses - fuel injected models
* Distributor cap cracked or tracking internally
* Incorrectly adjusted valve clearances - B6 and E Series engines
* Faulty HLA Adjuster(s) - B3 and B5 engines
* Uneven or low cylinder compressions
* Disconnected, leaking or perished crankcase ventilation hoses