Posted to Technical Discussion Forum on 6/27/2013
The power of built in scan tool functions
I had a 2005 Ford Taurus come my way requiring a
drivability diagnosis. It had a dead misfire, and even
taking the misfire into account it was idling very poorly. I
checked Continuous Mode DTCs, the P0171 Freeze
Frame, and PCM KOEO codes . There are many ways to
handle this vehicle, but I'll share what I did with my IDS.
First, I checked power balance. Next, I checked
relative compression. I then checked relative injector
flow. I was already in the Fuel System tests, and I did
have a P0171 so I thought I'd just check running fuel
pressure and fuel pressure leak down really quickly.
I already knew where I was going for the misfire, but before
I got out of the driver seat I thought I'd just peek at
some scan data.
At this point I already know I have an ignition system
related misfire. Not hard to guess, certainly not hard to
determine through other methods. I was able to quickly
eliminate/confirm a variety of things and narrow my testing
down to the most pertinent area.
I put my capacitance pickup on cylinder #3's ignition cable
and checked Power and Waste secondary waveforms.
The spark is not occurring in the combustion chamber. I put
a spark tester set to 20kv on the end of the ignition cable,
and a low amp probe around the coil common power wire.
No spark at the spark tester.
100k on the odometer, original plugs, orginal ignition
cables, and a defective coil. A set of plugs and cables,
with a new coil and the misfire was corrected. A KAM Reset,
fuel trims back to normal, misfire gone, and away goes the
This was not a complicated failure, nor a complicated
diagnosis. This vehicle certainly could have been diagnosed
a number of ways utilizing a wide variety of tools and/or
methods. Still, the power of the built in test functions of
the Ford IDS for this vehicle made it a no risk, low effort,
high comfort diagnosis.
Shannon from California
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47 Replies Received