2003 Subaru Outback 2.5 H4 SOHC

Boxer Blues

So its been a while since my last blog.  Well summer has a funny way of doing that.  After a two week vacation to the desert southwest with my wife Kelli in our RV, my go get em' attitude with writing suddenly waned.  Well, I decided I work my way back into the saddle so to speak and found this baby above the perfect subject to get my writer's block on the defensive.

This particular 03 Subaru Outback was brought in with a complaint of intermittent rough running and check engine lamp. The warning lamp would come and go, whether or not the rough running was occurring at the time, according to the owner.  Hmm.  Whenever this light comes on... and this goes for any car built in the US after 1996, an alpha-numeric diagnostic code gets stored in the control units diagnostic memory.  Even after the light goes off, the code remains in memory for future retrieval (unless the battery gets disconnected).

Plugging into the vehicles diagnostic connector with the shop scan tool showed us a diagnostic code P0303.  This code points us to a misfire in the #3 cylinder.  A misfire occurs when any one of the criteria needed for proper combustion is NOT present, resulting in a cylinder not contributing power.  Well this certainly goes along with the rough running complaint.  Time to get dirty and do some investigations.

Removing the #3 spark plug wire and spark plug reveals some interesting information.  Click on the pics for a closeup, and you can see on the spark plug on the right has small black lines on it.  These lines are usually called tracking.  Modern day ignition systems make very high voltages. (40,000-60,000) volts to fire the plug.  This is a case where the path of least electrical resistance became the outside of the spark plug, rather than the normal path inside.  I run into this type of problem quite a bit, and it can happen to almost any vehicle.

You can see here the tracking has left marks on the plug wire boot shown on the left.  This happens because of old age, lack of maintenance, or perhaps the spark plugs were replaced without replacing the plug wire set.  I know it costs a little extra, but it can save you a trip to the shop down the road.

Whenever spark plug wires are replaced, the new set comes with a small tube of the di-electric grease. A small dab inside the plug boot will prevent the new boot from welding onto the new spark plug from extreme heat.  (Pardon the dirty thumb)

The last step to complete this job was to clean out the throttle plate.  The two photos here are before cleaning and after cleaning.  The reason they get dirty in the first place is because of vapors left behind in the engine after shutting it down ted to condense on the cooler parts of the engine.  The plate happens to be about the coolest!

This "coke" builds up over time and can cause several problems from stalling, hesitations, to idle surging.  Figured since we were making it good on the freeway, might as well make it good at idle too!

Oh yeah in the upper photo here, there is a piece of rubber caught between the throttle housing and air cleaner.  I fixed that too.

Till next time.....  Chris