04 Forrester missing on damp mornings

[4orrester]

My 04 Forrester is missing on wet mornings - enough to get the "check
engine" light to come on. Once warm, everything is ok. There are 136k km
on the electrical parts of the engine, but only 50k km on the short block.
Had the thing undercoated about 3 weeks ago with "Rust Check".

My guess is probably plug wires ($134.00 from dealer) or coil ($218.00 from
dealer). Neither are a huge expense, but more than expected.

Any thoughts from the group? Will the OBC put the engine in "rich" mode
after it detects a fault? Will it clear automatically or do I have to clear
the memory with an OBD reader? Gas mileage has dropped a bit. I have yet
to start it up in the dark and have a look for leaking plug cables - its
been raining and very windy here for the last week from a storm front.

Thanks in advance.

 

[1 Lucky Texan]

My 04 Forrester is missing on wet mornings - enough to get the "check
engine" light to come on.  Once warm, everything is ok.  There are 136k km
on the electrical parts of the engine, but only 50k km on the short block..
Had the thing undercoated about 3 weeks ago with "Rust Check".

My guess is probably plug wires ($134.00 from dealer) or coil ($218.00 from
dealer).  Neither are a huge expense, but more than expected.

Any thoughts from the group?  Will the OBC put the engine in "rich" mode
after it detects a fault?  Will it clear automatically or do I have to clear
the memory with an OBD reader?  Gas mileage has dropped a bit.  I have yet
to start it up in the dark and have a look for leaking plug cables - its
been raining and very windy here for the last week from a storm front.

Thanks in advance.

It does sound like classic high voltage problems. If you want to track
this down for DIY purposes, one trick is to look around at night for
arcing as you seem to know. Also, using a mister bottle to isolate -
say - one side of the car from the other or coil/wires etc. is an old
trick. Did the misfire code(s) come from the same cyl? If it's all
cylinders - and has persisted for more than a coupla tanks of gas,
could be igniter/coil (does you car have a single 'coil pack' or
individual coils?) if the code is always the same cylinder - could
just be that wire, or even a single bad plug. You'd expect a plug not
to be sensitive to moisture - though I suppose the ceramic could
crack....?????

If the car is experiencing a miss, gas mileage will drop. After you
make any repairs/adjustments the car will 'adapt' after a few drive
cycles, and everything should be OK.

 

[StephenH]

My 04 Forrester is missing on wet mornings - enough to get the "check
engine" light to come on.  Once warm, everything is ok.  There are 136k km
on the electrical parts of the engine, but only 50k km on the short block..
Had the thing undercoated about 3 weeks ago with "Rust Check".

My guess is probably plug wires ($134.00 from dealer) or coil ($218.00 from
dealer).  Neither are a huge expense, but more than expected.

Any thoughts from the group?  Will the OBC put the engine in "rich" mode
after it detects a fault?  Will it clear automatically or do I have to clear
the memory with an OBD reader?  Gas mileage has dropped a bit.  I have yet
to start it up in the dark and have a look for leaking plug cables - its
been raining and very windy here for the last week from a storm front.

Thanks in advance.

pull the wires off the coil and look. Sometimes one coil post and wire
will be badly corroded. Also get the codes read and see if its a
specific cylinder.

 

[4orrester]

My 04 Forrester is missing on wet mornings - enough to get the "check
engine" light to come on. Once warm, everything is ok. There are 136k km
on the electrical parts of the engine, but only 50k km on the short block.
Had the thing undercoated about 3 weeks ago with "Rust Check".

My guess is probably plug wires ($134.00 from dealer) or coil ($218.00
from
dealer). Neither are a huge expense, but more than expected.

Any thoughts from the group? Will the OBC put the engine in "rich" mode
after it detects a fault? Will it clear automatically or do I have to
clear
the memory with an OBD reader? Gas mileage has dropped a bit. I have yet
to start it up in the dark and have a look for leaking plug cables - its
been raining and very windy here for the last week from a storm front.

Thanks in advance.

pull the wires off the coil and look. Sometimes one coil post and wire
will be badly corroded. Also get the codes read and see if its a
specific cylinder.

I found the culprit ( I think!). The single coil pack on top has what
appears to be a wormhole through the bakelite just under where the plug wire
attaches on #3. There was also the telltale white streak of an arc
radiating from the boot of #3 wire at that point. I put some Si grease on
it for now to seal out the moisture. I have no OBD reader, but should
probably buy one. The check eng light is on constantly now. Will the fault
clear itself or do I have to clear it by disconnecting the negative battery
terminal or use an OBD reader? We've had 146% of normal November rainfall -
and it is only the 7th, with 4 more days of rain on the way.

Thanks everyone!

 

[Jack Countryman]

pull the wires off the coil and look. Sometimes one coil post and wire
will be badly corroded. Also get the codes read and see if its a
specific cylinder.

I found the culprit ( I think!). The single coil pack on top has what
appears to be a wormhole through the bakelite just under where the plug wire
attaches on #3. There was also the telltale white streak of an arc
radiating from the boot of #3 wire at that point. I put some Si grease on
it for now to seal out the moisture. I have no OBD reader, but should
probably buy one. The check eng light is on constantly now. Will the fault
clear itself or do I have to clear it by disconnecting the negative battery
terminal or use an OBD reader? We've had 146% of normal November rainfall -
and it is only the 7th, with 4 more days of rain on the way.

Thanks everyone!

Some of the auto parts stores will read/clear codes for you for
free...on the assumption that you are going to buy the parts to fix the
problem from them. FAS (Fleenor's Auto Service) is one such in
Indiana...don't know where you are/who the stores are there, or which
would do it for free in your area?

 

[1 Lucky Texan]

pull the wires off the coil and look. Sometimes one coil post and wire
will be badly corroded. Also get the codes read and see if its a
specific cylinder.

I found the culprit ( I think!).  The single coil pack on top has what
appears to be a wormhole through the bakelite just under where the plug wire
attaches on #3.  There was also the telltale white streak of an arc
radiating from the boot of #3 wire at that point.  I put some Si greaseon
it for now to seal out the moisture.  I have no OBD reader, but should
probably buy one.  The check eng light is on constantly now.  Will the fault
clear itself or do I have to clear it by disconnecting the negative battery
terminal or use an OBD reader?  We've had 146% of normal November rainfall -
and it is only the 7th, with 4 more days of rain on the way.

Thanks everyone!

Around here, Autozone and similar will read - but claim they are not
allowed to clear - codes.

Disconnecting the battery, stepping on the brake pedal, and waiting
several minutes(10-15) SHOULD reset the ECU. Because the monitors will
need to complete, and, especially on older cars, because the ECU will
use the 'factory map', you will not pass most State emissions tests
and the car may run oddly for the first few drive cycles while the ECU
readjusts for older sensors.

If the check eng. light comes back on - do have it read as there may
be another problem. It is not uncommon to have several codes and some
folks don't scroll down past the first one on the readers.