MY 98 Forester question

[Jonathan Heard]

Help!

I have a 1998 Forester with 275000 miles which had developed a rough idle.
Since there were over 80k miles on the plugs and wires, we changed them.

After we changed the plugs and wires and we are still getting a CEL code,
P0304. The code definition is, Cylinder Number 4 misfire detected. We
checked the #4 plug, not apparent issue.

I tested the Coil Pack with an ohmmeter and it is good.

Looking for other ideas, no other issues or codes.

Thanks.

 

[Tony Hwang]

Help!

I have a 1998 Forester with 275000 miles which had developed a rough idle.
Since there were over 80k miles on the plugs and wires, we changed them.

After we changed the plugs and wires and we are still getting a CEL code,
P0304. The code definition is, Cylinder Number 4 misfire detected. We
checked the #4 plug, not apparent issue.

I tested the Coil Pack with an ohmmeter and it is good.

Looking for other ideas, no other issues or codes.

Thanks.

Hi,
Used OEM wires? One thing you can do is, in the dark open the hood and
while engine is running look if sparks fly around the #4 coil pack or
wires. Some times heat affects the coil pack. It'll look good when cold
but when hot, goes bad(intermittent).

 

[S.Hansen]

Help!

I have a 1998 Forester with 275000 miles which had developed a rough idle.
Since there were over 80k miles on the plugs and wires, we changed them.

After we changed the plugs and wires and we are still getting a CEL code,
P0304. The code definition is, Cylinder Number 4 misfire detected. We
checked the #4 plug, not apparent issue.

I tested the Coil Pack with an ohmmeter and it is good.

Looking for other ideas, no other issues or codes.

Thanks.

As its with the #4 you have to break it down. Coil- fuel injector (swap with
another cylender- be awaire the o rings will be bad and you should have a
two new sets with you) if you swap the injectors then the problem is the
injector. After that you need to do a compression check on the car and a
cylender leak down. At 275, I wouldent be surprised to see the engine
getting weak. I'm putting in a junkyard engine in my 98 forester real soon-
only 80K.

 

[Hachiroku $B%O%A%m%/(B]

Hi,
Used OEM wires? One thing you can do is, in the dark open the hood and
while engine is running look if sparks fly around the #4 coil pack or
wires

I just grab the wire with one hand, and a fender with the other.

If there's a bad wire, you'll know it!!!

(I actually did this once quite by accident, very early in my
experimenting with cars. Quite the eye-opener!!! Never did that again!

 

[Jonathan Heard]

Tony,

Still chasing this issue on the MY 98.

New Plugs, new wires and also a new coil block. ( We did see a lot of arcing
in the dark.)

Problem presists. Don't know the specific CEL code; but we suspect it is
the same code.

Additional question. If I were to remove one wire at a time, while it was
running and it quit, have I found a specific problem?

 

[Carl 1 Lucky Texan]

Tony,

Still chasing this issue on the MY 98.

New Plugs, new wires and also a new coil block. ( We did see a lot of arcing
in the dark.)

Problem presists. Don't know the specific CEL code; but we suspect it is
the same code.

Additional question. If I were to remove one wire at a time, while it was
running and it quit, have I found a specific problem?

In the 'old days' that would tell you if a specific cylinder were
'dead'. Basically, pulling the wire from the bad cylinder would make NO
difference. Then you could pursue spark plug or compression or other
issues specific to that cylinder. I guess that could still work if you
are having a bad miss at idle.


Carl

 

[Tony Hwang]

Tony,

Still chasing this issue on the MY 98.

New Plugs, new wires and also a new coil block. ( We did see a lot of arcing
in the dark.)

Problem presists. Don't know the specific CEL code; but we suspect it is
the same code.

Additional question. If I were to remove one wire at a time, while it was
running and it quit, have I found a specific problem?

Hi,
Pulling wire when engine is running is not a good idea. If you still see
sparks fly around in the dark, prob;lem is still there. high voltage os
leaking instead of going to plug. Try washing the engine with dtergent
at self serve car wash.

 

[Uncle Ben]

Tony,

Still chasing this issue on the MY 98.

New Plugs, new wires and also a new coil block. ( We did see a lot of arcing
in the dark.)

Problem presists.  Don't know the specific CEL code; but we suspect it is
the same code.

Additional question.  If I were to remove one wire at a time, while it was






- Show quoted text -

Suggestion: Spend a bit for a scanner you can use with your laptop to
read the codes and lots of performance data while you are operating
the car.

You can get one for under $100. Of the two I tried, I recommend
OBDCOM. The Auto Tap unit had a flaky USB connector and flaky
software.

Uncle Ben

 

[S]

Hi Jonathan!

Additional question. If I were to remove one wire at a time, while it was
running and it quit, have I found a specific problem?

Possibly, but I think that due to the way the coil packs work, both
plugs (i.e. 1 & 3 or 2 & 4) have to be connected for either to fire.

In this case, pulling one plug wire will kill two cylinders, and the
engine might well die as a result. Additionally, you might damage the
coil pack. As the high voltage pulse from the coil pack does not have
it's "normal" path to ground (thru the spark plug), it may arc
internally, which can leave a carbonized track. If this happens, that
is where the spark will go preferentially.

A better solution would be to disconnect one plug wire (with the
engine off), and either ground the end of the wire to the engine with
a screwdriver or the like, or insert another spark plug and lay that
on top of the engine such that it is grounded. Gives the spark
somewhere to go, right?

Beyond that, check the compression on all four cylinders. Should be in
the range of 140 to 160+ PSI, and fairly even across all four. Try
swapping injectors. Is the number four plug coming out black? All
should be a light tan color (on the electrode). If it's black, you
might have oil control issues; valve guide seals or oil control rings.
As a last resort, try another ECU.

Using an OBDII interface with real-time readout and data logging
capabilities can be very helpful in troubleshooting these kinds of
problems. I like the ElmScan products. http://www.scantool.net/

Hope this helps.

ByeBye! S.
Steve Jernigan KG0MB
Laboratory Manager
Microelectronics Research
University of Colorado
(719) 262-3101