Can anyone help the Newbie-- I want to help my local police cheif on his 1997 F150 5.4 engine. He gets intermitten misses or misfires. I beleive he has one of the coils breaking down . What I need it the voltage that these units put out or the best way to test the coil. I have teenagers and may have to pull the favor card sometime with the chief. Thanks for your input
Dan in IL

 

IF the engine has a miss start by inspecting the (as your facing the front of the truck) left rear coil/plug assy. the 97 has a heater hose that connects to an aluminum tube right over that cyl. see if you can see evidence of coolant leakage on that coil, if so the coil is probably shorted. the boot of the coil may have a rust colored residue. Your problem may be there. Is the MIL illuminated?

 

Pretty sure the heater hose problem did not appear until later model years (sometime after 2000).

Before worrying about the COPs, inspect/replace the spark plugs. Its much cheaper. Testing the resistance on the COPs is not a solid test. The best option for testing coils is to move them around and see if the miss follows a certain coil pack.

 

A basic non tech test is pull the wire from the coil at the dist.. Without shocking you self!, place the coil wire up to some metal with someone cranking the engine a bit. If the spark is blue it is good and progressively worse if it is green, yellow, red, none....