03-31-2010, 01:55 PM
Full Access Members
Join Date: Jun 2007
Location: Hartford, CT
Based on my experience with my 2000 5.4:
If you drive it 3 times (I think) and it misfires each time, the service engine light will come on.
Then, you can plug a scanner into the OBD II port (under the dashboard, below the steering wheel and to the right) and it will give you a code.
The code will tell you which cylinder is misfiring.
If you don't have a scanner, there are autoparts stores that can scan it for free (I know Autozone does for sure).
Cylinders are labeled 1-8 (obviously). Passenger side is 1-4, driver side is 5-8. 1 and 5 are at the front of the engine; 4 and 8 are at the back.
Then, remove the coil on plug assembly. It is held in with one bolt, plus an electrical connection and sits on top of the spark plug.
Once the coil is out, you can check the primary and secondary resistances using a multimeter.
Measure the resistance (in ohms) across the electrical connector (primary) and from the connector to the spark plug connection (secondary).
I don't know the specs off hand, but I know they are listed in the Haynes manual.
From my experience replacing two bad coils, I can say that the resistance can be correct and the coil may still be bad. This is particularly true when the misfire isn't at idle but only under acceleration or load (like going up a hill).
When you replace the coil, don't forget to use some kind of dielectric grease to protect both of the connections.
Finally, once it is all back together, it should take 3 cycles of normal driving w/o misfire to turn off the service engine light and clear the code.
Hope that helps! Goodluck!
2000 Ford Expedition XLT 5.4L A4WD 3.55 LS
-Medium Wedgewood Blue w/gray leather, 3rd row seat, rear heat/ac, tow package, 20% tint
-22x9.5" Wired WI30Rs with 305/40's (Wanli S-1098)***For Sale***
-16x7" Ford alloys with LT285/75 (Definity Dakota AT)
-PAC PXPX, Alpine PDX 4.150, CDT Audio CL-S60 w/TW-25, Elemental Designs 11.kv, Raamat BXT/Ensolite