Possible Bad Coil? (P0353, P0302, P0306)

[Bob Kunkle]

My ST has had a stumble while idling. I get P0353 as a pending DTC while idling and P0302 & P0306 while holding rpm at 2000RPM. I replaced the plugs since the truck has 100,000 miles and the #3 plug wire had quite a bit of corrosion so I ran out and got cables. Replacing these items has not resolved the rough idle.



1. I also checked the low side of the coils and the connection looks fine.

2. I used a known good wire from the old set.

3. Used an old plug from another cylinder



Any thing else before I run out in the morning and get a coil?

 

[Boodrodon Dykes]

Not sure if you know how to measure resisitance, but If you have a Ohmmeter or a DMM, measure the resisitance of the coils. Not sure about Ford specs, but general specs for Primary coil is low digit (such as 2-5) Ohms, and Secondary is low digit (such as 5-8) K Ohms. If meter reads O.L., coil is open and its bad. Good Luck!





Boodro

 

[Todd Z]

IF the place will take the coil back go for it, IF not try to find a used one to test with..



Todd Z

 

[scott degroot]

Why not get a pair of insulated pliers and pull the suspect cylinder plug wire off at the coil and see if you have spark while it is running. If you don't have any spark then the next thing to check is the coil driver form the pcm. Get a test light adn hook it to the positive battery terminal, unplug the coil connector and have a helper crank the engine while you probe the 3 wires that fire the individual coils. The red/ light green wire is battery voltage, the other 3 wires are the coil trigger wires, while the engine is cranking and you have the test light probing the trigger wires the test light should flash. If the test light flashes on all 3 trigger wires but you don't have any spark when pulling off a spark plug while the engine is running you have a bad coil pack.