Wednesday, July 1, 2015

Adventures in Auto Repair

I highly recommend that you replace your Ignition Coil, Spark Plugs, and Wires every 220,000 miles, whether they need it or not.  :-)

My $1800 1996 Sable Stationwagon began running really rough at idle.  It seemed to run OK at higher speeds, but at idle, it would almost die and would misfire bad enough that the check engine light would start flashing.  (That is the pull-over-and-stop-NOW indicator.) It would backfire when accelerating and have little power until higher speeds.  After a couple of minutes at higher speeds the light would quit flashing.

I was also having trouble with the transmission.  I suspected that the valve body was cracked.  It would hunt back and forth and slam into gear when slowing down and speeding back up at low speeds.  This got worse and worse.  Finally, it got so bad that I could no longer use overdrive -- I had to drive in D all the time.

I was also having temperature issues.  The engine didn't ever actually overheat, but the temperature would cycle up and down over several minutes.  I suspected a 'sticky' thermostat that was responding slowly.


Last weekend, I replaced the ignition coil, spark plugs, and wires.  I expected to have a LOT of trouble getting to the back three plugs and getting the plugs out of an aluminum engine.  Given the difficulty I have (age and condition) doing anything, it all went unusually easy.

However, when I started it up, it ran uniformly rough at all speeds.  I had a 50/50 chance of getting #1 & #2 wires swapped (they were hard to see and the wires were both the same length), so I swapped them.  It was MUCH worse.  OK, that wasn't it!  I checked all the connections.  Everything was plugged in good.

The guy at Advance said I might have a bad (brand new) coil.  I bought an OBD II DTC Code Reader.  It said that (only) 4 & 6 were misfiring.  The coil pack has 3 coils which fire the cylinders in pairs.  4 & 6 were NOT a pair.  That means it wasn't the coil.

I had been very careful with the front three wires.  They were very easy to get to and easy to trace.  And I noticed the odd pattern on the coil.  The back 3 were 1, 2, 3.  The front three were NOT 4, 5, 6.  So I had carefully put them in the order 4, 6, 5.

Since the Reader indicated only 2 cylinders, I dug the old coil out of the trash so I could read the numbers.  (The new one didn't have numbers.)  The order was 1, 2, 3 / 6, 5, 4.

I unplugged the easy-to-get-to wires that I was sure were right.  I carefully traced each one and put them back (correctly).  The car now runs perfectly.

Not only that!  The transmission shifts smoothly now!  The thermostat works good!  It doesn't kick in and out of overdrive going up hills!  The sun is shining and birds are singing!  Wow!

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