Yes, it could be a bad coil that breaks down under load.
It could also be a cracked spark plug (sometimes a tech might accidentally crack one when installing them).
If a scanner is used which can monitor engine data (Snap-on scanners as well as others can do this) while the engine is running (even being driven) the technician can go into the computers "history" where he will find a record of which cylinder misfired and the number of times it misfired. This would identify the cylinder at fault and from there he could narrow down the causes by the process of elimination.
Thursday, December 12th, 2013 AT 5:01 AM