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Dimitri Survives Coil on Plug Hell
To all SHO owners,
For the last three months, my wife's 97
SHO put me through hell.
The problem began with a slight misfire that
could be felt at idle. My first assumption was that she may have gotten
some "bad gas", so I told her to finish out that tank, at which
point I would replace the fuel filter. No Luck.
Next, I figured that since the car has 85,000
miles on the original spark plugs, it might be time to replace them, so based
on recommendations I purchased 8 brand new Bosche Platinum +4 Plugs (not
cheap) (refer to http://www.v8sho.com/SHO/SparkPlugChoice.htm).
The first time I had to remove the intake
manifold expansion tank, it took me and my cousin about 1.5hrs (refer to http://www.v8sho.com/SHO/HowToPulltheSurgeTankforRearPlugChange.htm).
Notice I said the "first time". I
replaced the plugs, reassembled the engine (another 1hr), but, still...No
At this point, I purchased a FORD Factory
Service Manual CD-ROM for $20 and an OBD II scanner on eBay for $140 and
hooked it up. I got P0304 Cylinder 4 Misfire.
My next guess was that there may be a faulty
coil pack on cylinder 4, so off comes the intake manifold expansion tank for
the second time. I perform an electrical
resistance test with my digital volt-ohm meter to verify that electrical
resistance on each coil is between 5-6 ohms (refer to http://www.v8sho.com/SHO/MissfiresandCoilTests.htm).
All of the coils pass the test, so I swap the coils front to back, hoping that
the misfire would change cylinders, therefore revealing the faulty coil.
Once again,...NO LUCK!!!
At this point, things were getting
worse. After the coil pack swap, my SHO began to stall when hot, but
only if it was driven hard. After the stall, it would hardly start and
if it did, it ran VERY BADLY. The Service Engine Soon light (MIL) came
on and I got a P0743 Torque Converter Clutch Circuit Electrical
and P0103 Mass or Air Flow Volume High Input. The
Misfire code, by the way, had NOT come back.
After doing some digging in the FORD Service
CD-ROM, with its overly complicated navigation, I found that the TCC (P0743) code
could be the result of the MAF(P0103) code. I had the MAF bench tested
by Jerry's Leesburg Ford, and it came up fine. Running out of ideas at
this point, I took the car to Jerry's Leesburg Ford to be diagnosed.
Their results were shocking, to say the least. Apparently, the COIL
PACKS <---(I say that with much hatred!) were creating a "noise"
on the electrical circuits which was causing the PCM to "crap
out" and give incorrect instructions to the fuel injection system (refer
The problem was that they couldn't tell me which coil packs were doing it
because that required "sophisticated diagnostic equipment" which
they didn't have.
Once again,...OFF COMES THE INTAKE MANIFOLD
EXPANSION TANK!......for the third time!
I purchased one coil and it came to my
attention that it didn't rattle like the old one when I shook it, so I removed
another coil pack and shook it...then another, then another. They all
rattled as if their insides were loose. ALL OF THEM DID, so I bought
seven more and replaced them all......PROBLEM SOLVED!!! The SHO now runs
as if it were brand new ($800 later).
One of the last lines in the ALL SHO and NO GO article states, "While
this type of problem is not an everyday occurrence (fortunately), ignition
noise does exist and can cause some pretty unusual problems for us.".
(refer to http://www.v8sho.com/SHO/AllSHOandNoGo.htm)
How very untrue.
It seems to me that not only is this problem an everyday occurrence, I believe
that if all the coil packs failed at approximately 85,000 miles, they should
be considered a maintenance item and serviced in 80,000 mile intervals.
Quite an expensive maintenance item, in my opinion!
I suppose that the only good thing to come
out of this is that I can now remove and reinstall the intake manifold
expansion tank in about 30-45 minutes and can identify every nut and bolt that
is involved in the process.
Good luck to the rest of you. I hope I have
saved some skinned knuckles and shouted obscenities.
Electrical Design/CAD&IT Support
E.K. Fox & Associates, Ltd.
Shouted Obscenities? Who me? ;-)
Other folks have suggested, replace one coil replace them all.