1996 Outback Legacy Emissions Problems - Need help trouble shooting

[Sparky19]

I am getting only about 13 mpg in my newly acquired Outback and am new
to diagnosing these problems and need a little help with where to go
without replacing everything. I did a OBDII read and exported the
data to Excel :
Test was initiated beginning at idle with engine warm (coolant temp
reads 180-190 deg F). Idled for 1:34 (1 minute, sec)and the
increased rpm to ca. 2000 rpms for about a1.5 minutes and then dropped
rpms back to idle.

Mass Air Flow Sensor : Seems fine throughout the test reading steady
at idle (0.4-0.45 lbs/sec) and increased (2000) rpms (1.0-1.15 lbs/
sec).

Timing Advance for Cylinder 1: 15 deg at idle and 44 deg at 2000 rpm
(steady on both)

Short Term Fuel Trim: -25% at idle and increase in rpm, but up to 0%
when rpms went from 2000 back to idle and fell gentle and steadily
back down to -25%. Seems I'm running rich, but why?

Long Term Fuel Trim: Fluctuating from 26% to 27% at idle and constant
at 27% at 2000 rpm

Intake Manifold Absolute Pressure: 4psi to 4.5psi at idle and decrease
to 3.5 at 2000 rpm

Upstream Oxygen Sensor Voltage: Varies from 0-0.4v, but moreover 0.2
to 0.4v. It did increase to 0.5 after going from high rpm back to
idle and then drop back to previous levels once at idle

Downstream Oxygen Sensor Voltage: Almost the same as the upstream O2
sensor, but about a 0.1v lower and looks like it had a time lag of 2-3
seconds. Does this mean my catalytic converter is shot?

Upstream Oxygen Sensor Fuel Trim: At -22% to -25% except when rpms
drop from 2000 to idle and then it jumps up to -1.5% and then steadily
decrease back to -25% in about 1.5 minutes

Downstream Oxygen Sensor Fuel Trim: Always at 0. I'm guessing that
the car just doesn't register that parameter.

If I can find out how and where to post the charts, I will ( I can do
it in PDF, Excel, or Word)

Thanks in advance....

Sparky

 

[AS]

The manifold abs. pressure reading does not seem normal.

The vacuum reading at idle should be about 18" Hg (mercury), and
normally the reading should be in the 1 or 2 volt range. The int.
manifold pressure senson or its circuit seems to be out of whack.

Good luck!

 

[Sparky19]

Yes, you are right - I didn't see that. I guess I need to test it
with the key on and engine off to see if it reads atmospheric pressure
correctly. If so that part is a good $200. Is there a way to fix
that? I'll look at it tonight and see if I can't take it off and
clean it if it doesn't read the right barometric pressure.

Thanks! I'll report back.

Sparky

 

[Carl 1 Lucky Texan]

Yes, you are right - I didn't see that. I guess I need to test it
with the key on and engine off to see if it reads atmospheric pressure
correctly. If so that part is a good $200. Is there a way to fix
that? I'll look at it tonight and see if I can't take it off and
clean it if it doesn't read the right barometric pressure.

Thanks! I'll report back.

Sparky

There have been folks who have used K&N type (oiled) filters and have
needed to clean the filament to restore the MAF sensor function. But if
you have a MAP then I dunno.

I wouldn't discount the possibility of also having a bad Engine Temp
Sensor(not Temp gauge sender) - it can fail in such a way as to keep the
ECU in 'cold engine/choke' mode which will produce very poor gas
mileage/rich conditions.

Carl

 

[Sparky19]

Today I replaced the MAP sensor with another and the problems still
exist. MAP reads the same (about 4.5 psi - that's , but this time I
took the vacuum hose off the MAP and it read 14.5 psi (Barometric
pressure ). So it is reading right, it's just that the 10 psi
difference is the manifold pressure (vacuum), right? And you're
saying the OBDII data should be reading 9psi? Does Subaru have a
different zero point for the pressure?

No K and N filter installed an the MAF is reading good - I even
cleaned it to make sure.

Also when car is running, the OBDII says it's in a closed loop mode,
so not that.

I'm still wondering about the downstream O2 sensor reading about what
the upstream does. Catalytic converter?

Sparky

 

[AS]

Now you seem to have the proper change in the MAP reading reading (or
was it a typo in the original message?). Remember that the map reads
absolute pressure, so your 4.5 psi correspond to a vacuum of about 18 in
Hg. Accelerating the engine should increase the pressure, not drop it as
you stated in the original message.

The other sensors appear normal to me.

Have you tried the usual stuff? Tire pressure, alignment, air filter
replacement, spark plugs condition, ignition wires resistance, engine
compression? Is the tranny slipping, brakes sticking? Most of this
stuff can be checked without replacing anything.

Good luck!

 

[AS]

By the way, do you have an emissions problem, failed a test?

 

[brian]

By the way, do you have an emissions problem, failed a test?








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