haystack. brand of octane boost (which shall
As I removed the spark plugs I remain nameless), but the contents
noticed a reddish coating on the elec- didn’t list any metallic additives.
trodes (figure 5). Could that fouling I still don’t know if the fouling was
cause an intermittent ignition misfire? a result of additives from the gas or the
Perhaps the misfire was light enough bottle of octane booster. And I’m still
not to be noticed at low speeds or even shocked at the amount of plug fouling,
heavy load because the unlocked con- especially given the coil-on-plug igni-
verter would act as a cushion. tion system.
I remembered working on a After installing a fresh set of man-
Thunderbird with an AOD and a bad ufacturer-recommended spark plugs,
plug wire causing a shudder in over- the vehicle was happy again. The shud-
drive (remember, the intermediate shaft der was gone.
locked directly to the converter cover in I remained a little curious though
Figure 5: Reddish plug fouling:
overdrive). I also remembered the guy about the converter slip. I elected to
fuel additives?
at the dealer mention something about make additional data recordings and
the red color on the plugs. He thought monitor clutch slip now that the car was seem to work just fine, as long as the
it was the fault of the coils and replaced fixed. Under the same type of condi- engine is happy.
them. tions I found the converter clutch slip I’m glad this one is fixed. Now I
Seeing the red fouling for myself value to be much lower. It was fluctuat- can ponder other important questions,
gave me flashbacks to plug condition ing less than 10 RPM (figure 6). such as: Why did the chicken cross the
charts in school and I remembered it So apparently (at least on this vehi- road?
could be certain metallic-based fuel cle) the chicken-or-engine misfire can Matt Dixon is an Assistant Professor
additives. I’d recently added a bottle of cause the egg of converter clutch slip. at SIUC’s Automotive Technology pro-
octane boost to get a little more oomph All attributed to something simple like gram, where he specializes in vehicle
out of the engine via spark advance. I fouled plugs that got overlooked for too stability, ABS/TCS systems, emissions
returned to the store and checked the long. The low speed lockup points all and driveability.
Figure 6: Without engine misfire, the calculated converter slip never exceeded a few RPM.
GEARS March 2010 35
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