The key to successful engine troubleshooting is effective observation; notice when strange smells or sounds occur and, if they are intermittent, what causes them to occur. Pay attention to unusual mechanical activity, unexpected sounds, engine misfires and smoke-filled exhaust when troubleshooting a vehicle's engine.
An automotive engine that hesitates during acceleration or feels like it generally lacks power may have a dirty air filter, an ignition system problem or a clogged fuel filter. If the engine uses a carburetor, that device may need to be repaired or replaced to get the fuel moving efficiently through the rest of the engine.
Blue or gray exhaust smoke indicates that the engine's piston rings, valve guides or valve seals might be worn out and require replacement. Piston ring and valve seal problems may also cause the engine to use more oil than usual, keeping the oil level unnaturally low. If the vehicle's exhaust produces white vapor, it may have a defective cylinder head gasket or a transmission fluid leak through its vacuum modulator. Replace these devices to resolve the problem.
Consistently low oil levels may indicate a leak somewhere in the engine's oil system due to a cracked tube or a faulty gasket. Another possibility is that the engine is burning oil unnecessarily due to worn out piston rings.