96 Outback Rough Idle...

[rick]

Hi -

Recently my 96 Outback (85k mi) has developed a really rough idle. At a
stop it kind of bucks a bit, rpms bounce a bit, but nothing huge... You
can definitley hear the putt-putt-putt. At higher rpms the "putt" goes
away... though I think it still exists... it's just too fast for my
ears to detect.

Plugs / Wires / Fuel filter have only 20k miles (changed by Subaru)...
my fuel milage *has been* less than favorable ( < 18 mi/gal city). I
was under the hood yesterday and I couldn't detect any arc-ing from the
wires....Oh, and NO check-engine-light.

My "spidey senses" says it's the fuel pump, so I picked the pump/screen
up last night, and I'll install it this afternoon...

Should I be looking for anything else while I've tearing through the
car?

-Rick

 

[Sparky Polastri]

Check the oxygen sensor. Mine (2001) did exactly the same type of stuff and
weirder.

Turned out the O2 sensor went flakey/bad.

Good news it's a fairly cheap repair. Though I am suprised you don't have
an error code for that.

Your computer is probably running the engine on "limp home" mode, wasting
lots of gas and lacking a bunch of power.

 

[soggydorito]

Hi -

Recently my 96 Outback (85k mi) has developed a really rough
idle. At a
stop it kind of bucks a bit, rpms bounce a bit, but nothing
huge... You
can definitley hear the putt-putt-putt. At higher rpms the
"putt" goes
away... though I think it still exists... it's just too fast
for my
ears to detect.

Plugs / Wires / Fuel filter have only 20k miles (changed by
Subaru)...
my fuel milage *has been* less than favorable ( < 18 mi/gal
city). I
was under the hood yesterday and I couldn't detect any arc-ing
from the
wires....Oh, and NO check-engine-light.

My "spidey senses" says it's the fuel pump, so I picked the
pump/screen
up last night, and I'll install it this afternoon...

Should I be looking for anything else while I've tearing
through the
car?

-Rick

I have a 96 Impreza Outback that does something similar although maybe
not quite so bad. I changed plugs and wires and was considering the
fuel filter. O2 sensor also went through my mind. Let me know if you
find out what the problem is for sure.

 

[Edward Hayes]

I would first clean the throttle body and get a bottle of Techron
concentrate fuel system cleaner. Might also be some water in the gas.

 

[rick]

Sparky et al -

*Finally*, just yesterday, the CEL came on after a real fit, and I was
able to get some codes: EGR Malfunction, and Mis-Fires on Cylinders 1
and 3...

Today I replaced the BPT (back pressure transducer), a hose/filter from
the pressure exchange solenoid (suggestion from the local subaru
mechanic), and one of the EGR solenoids... I tested all of the other
solenoids using a SWEET technique that the Subi mechanic told me:

.... under your dash, towards the center console are two hanging wires
with green connecters (male and female)... if you connect them, and
turn the key to "on"... you'll see you check engine light flashing...
under the hood, the solenoids and the fans are all going through their
on and off phases. I was able to use this to test the solenoids (by
blowing into them, and feeling them open and close).

So.... with all of the parts replaced, I still have a broken car....
I'm a bit hesitant on the O2 sensor since I'm not getting an error
code... Any other suggestions?

Oh... an observation....while letting the car run for a bit, I *DID*
notice liquid sputtering from my tail pipe... water maybe? Is this
normal?

thanks for the help!

-Rick

 

[marcwert1]

I have a 96 Impreza Outback that does something similar
although maybe not quite so bad. I changed plugs and wires
and was considering the fuel filter. O2 sensor also went
through my mind. Let me know if you find out what the problem
is for sure.

is the idle rough or is it high like 1000 rpm and sometimes drops to
600 rpm. is it cyclic or mostly high. i have had worn plugs cause
rough idle and low power