Q: how to tell if timing chain is bad

Hello and thank you for contacting YourMechanic. Misfires can be caused by sloppy timing chain, spark plugs and wires not working, injectors not working, or a problem within the engine. To check the timing chain, get a timing light and hook it up to the battery and hook up the inductive pickup to the number 1 spark plug wire. With the engine running, shine the test light onto the harmonic balancer and see if the timing light is steady or if it moves around. If the light moves around, then the timing chain is loose and it needs replaced.

Check the spark plug wires for any spark. Then check the spark plugs for any burn spots or if the spark plug has fuel on it. Check the injectors with the engine running by pulling off the harness to each injector one at a time. If the engine changes tones and stumbles then the injector is working. If there is no change, then the injector may be not working. If the compression to the engine is 220, then there is a good seal to the combustion chamber and it leads to the timing chain, ignition, and fuel to cause a random misfire.