97 Outback Undriveable: serious sensor issues, white smoke from exhaust and stalling

[Kyle.Mack]

I just bought a 1997 Subaru Outback (2.5L) with 44K miles for $6200 two
weeks ago. Great deal I thought... I had it checked by a mechanic,
drove it for a while, and found it to be in great shape. Since I bought
it, I have had to have it towed to a shop twice because it stalled
after freeway driving and became undriveable. I could start it again
but every time I tried to give it gas, it would sputter and die. If I
let the engine get cold, everything returns to normal. The details to
the best of my knowledge are below. I would greatly appreciate any help
you could give me to diagnose the problem. Thanks in advance!

Incidents so far:
The car drives fine around town. Everything seems to work well until I
try to drive it at highway speeds for 10 minutes or so. The idle is
good, acceleration is good, slight lifter noise but no knocking.

Incident 1:
We had previously driven about 30 miles on the highway with no incident
and had driven on short jaunts around town with no problems. I had been
driving for twenty minutes or so and started down the freeway, after
about 5 minutes the check engine light came on. I came to a stop and
the engine started to idle roughly, like it was struggling to stay
going. I tried to accelerate from stop and the engine died. After that
I tried to start it 6 or 7 times. Each time the engine would start and
idle okay, but as soon as i pressed the accelerator the engine would
die. I tried gentle acceleration and revving it high in nuetral then
popping it quickly into drive. Each time the engine died. I let the car
sit for 30 minutes, started again, and got the same result.

I called a tow truck, which took about 45 minutes and towed it into the
shop. By the time I got it into the shop, the car basically ran fine.
The shop checked the OBDII codes and found: Knock Sensor and O2 Sensor.
I also found there were recalls for alternator and throttle body
issues, so I took it into the dealer. Neither one was defective
(according to them.) After all this, the car ran perfectly again, with
no check engine light, and I was able to drive around town for a few
days without incident.

Incident 2:
After a few days, I changed the air filter and filled up with premium
gas. Everything was running perfectly for about 30 minutes. Once again
the check engine light came on on the highway. I noticed that when I
would slow down, I got the same chugging, low idle behavior. I
continued to drive and hit some hilly sections of the highway. I
noticed that when I tried to accelerate up the hills, I would push the
peddle to the floor but the engine had very little power. After a few
seconds, the engine would "catch" and normal power would resume. During
this time, the check engine light would come on and off again
eratically. A few miles later, I got off the highway and came to a
stop. The engine chugged and died. I tried starting it a few times, but
was unable to keep the engine going. White / Blue smoke was coming from
the exhaust and there was a serious smell of gas.

I let the car sit for about an hour and tried it again...same behavior:
chugging engine, white smoke, strong smell of gas. The check engine
light was blinking as I tried to start it. I called another tow truck,
which took about 2 hours to get into the shop. By the time I got there
and started it again, there was still smoke coming from the exhaust and
the check engine light was on, but the car had noticeably improved. By
the time the shop looked at it, everything ran fine, there was no
smoke, the check engine light was off, and there were no codes.

Has anyone seen behavior like this before? The mechanic told me flat
out that he is totally confused by the problem and thinks it could be
related to the Knock Sensor, Air Flow Meter, O2 sensor, or Coolant
Sensor...I don't know even how to diagnose it, let alone fix it,
because the only way to make it happen is to drive long enough away
from home to the point that I have to tow it back.

I read online about a specific knock sensor problem that causes
hesitation, and I think this could have something to do with it, but
every piece of advice seems to be about Gary's Fix: a home built
electrical work-around that de-sensitizes the knock sensor, but I can't
find any info on it except for an outdated web page. Does anyone know
what he did?


Please, please help me!!!

Incidentally, we were supposed to drive the car up to portland this
weekend but we can't move, because we can't drive it more than a few
miles.

THANKS

 

[Carl 1 Lucky Texan]

I just bought a 1997 Subaru Outback (2.5L) with 44K miles for $6200 two
weeks ago. Great deal I thought... I had it checked by a mechanic,
drove it for a while, and found it to be in great shape. Since I bought
it, I have had to have it towed to a shop twice because it stalled
after freeway driving and became undriveable. I could start it again
but every time I tried to give it gas, it would sputter and die. If I
let the engine get cold, everything returns to normal. The details to
the best of my knowledge are below. I would greatly appreciate any help
you could give me to diagnose the problem. Thanks in advance!

Incidents so far:
The car drives fine around town. Everything seems to work well until I
try to drive it at highway speeds for 10 minutes or so. The idle is
good, acceleration is good, slight lifter noise but no knocking.

Incident 1:
We had previously driven about 30 miles on the highway with no incident
and had driven on short jaunts around town with no problems. I had been
driving for twenty minutes or so and started down the freeway, after
about 5 minutes the check engine light came on. I came to a stop and
the engine started to idle roughly, like it was struggling to stay
going. I tried to accelerate from stop and the engine died. After that
I tried to start it 6 or 7 times. Each time the engine would start and
idle okay, but as soon as i pressed the accelerator the engine would
die. I tried gentle acceleration and revving it high in nuetral then
popping it quickly into drive. Each time the engine died. I let the car
sit for 30 minutes, started again, and got the same result.

I called a tow truck, which took about 45 minutes and towed it into the
shop. By the time I got it into the shop, the car basically ran fine.
The shop checked the OBDII codes and found: Knock Sensor and O2 Sensor.
I also found there were recalls for alternator and throttle body
issues, so I took it into the dealer. Neither one was defective
(according to them.) After all this, the car ran perfectly again, with
no check engine light, and I was able to drive around town for a few
days without incident.

Incident 2:
After a few days, I changed the air filter and filled up with premium
gas. Everything was running perfectly for about 30 minutes. Once again
the check engine light came on on the highway. I noticed that when I
would slow down, I got the same chugging, low idle behavior. I
continued to drive and hit some hilly sections of the highway. I
noticed that when I tried to accelerate up the hills, I would push the
peddle to the floor but the engine had very little power. After a few
seconds, the engine would "catch" and normal power would resume. During
this time, the check engine light would come on and off again
eratically. A few miles later, I got off the highway and came to a
stop. The engine chugged and died. I tried starting it a few times, but
was unable to keep the engine going. White / Blue smoke was coming from
the exhaust and there was a serious smell of gas.

I let the car sit for about an hour and tried it again...same behavior:
chugging engine, white smoke, strong smell of gas. The check engine
light was blinking as I tried to start it. I called another tow truck,
which took about 2 hours to get into the shop. By the time I got there
and started it again, there was still smoke coming from the exhaust and
the check engine light was on, but the car had noticeably improved. By
the time the shop looked at it, everything ran fine, there was no
smoke, the check engine light was off, and there were no codes.

Has anyone seen behavior like this before? The mechanic told me flat
out that he is totally confused by the problem and thinks it could be
related to the Knock Sensor, Air Flow Meter, O2 sensor, or Coolant
Sensor...I don't know even how to diagnose it, let alone fix it,
because the only way to make it happen is to drive long enough away
from home to the point that I have to tow it back.

I read online about a specific knock sensor problem that causes
hesitation, and I think this could have something to do with it, but
every piece of advice seems to be about Gary's Fix: a home built
electrical work-around that de-sensitizes the knock sensor, but I can't
find any info on it except for an outdated web page. Does anyone know
what he did?


Please, please help me!!!

Incidentally, we were supposed to drive the car up to portland this
weekend but we can't move, because we can't drive it more than a few
miles.

THANKS

There are tests that can be performed for most of those sensors.
Additionally, at least 2 of them are relatively cheap, easy enough to
get to and could easily be bad at 44K to make them very tempting(temp
sensor and front O2). It does seem as if the Engine Temp sensor COULD be
the (or one of the) problem if the car consistently runs well when cold
and seems 'rich' or choked after warmed up. And that sensor is a known
weak spot for some models (the color of the plastic housing is the
giveaway - maybe someone will recall or try searching at www.usmb.net).

A MAF might cause the problem you are experiencing, but it is an
expensive part (on some models, the sensor element alone can be changed
- saving quite a bit of money).

The problem seems too severe for the knock sensor ALONE to the problem.
I would rent or borrow a different car for out-of-town travel until this
is properly diagnosed and repaired.

Carl

 

[Michael Pardee]

I just bought a 1997 Subaru Outback (2.5L) with 44K miles for $6200 two
weeks ago. Great deal I thought... I had it checked by a mechanic,
drove it for a while, and found it to be in great shape. Since I bought
it, I have had to have it towed to a shop twice because it stalled
after freeway driving and became undriveable. I could start it again
but every time I tried to give it gas, it would sputter and die. If I
let the engine get cold, everything returns to normal. The details to
the best of my knowledge are below. I would greatly appreciate any help
you could give me to diagnose the problem. Thanks in advance!

Incidents so far:
The car drives fine around town. Everything seems to work well until I
try to drive it at highway speeds for 10 minutes or so. The idle is
good, acceleration is good, slight lifter noise but no knocking.

Incident 1:
We had previously driven about 30 miles on the highway with no incident
and had driven on short jaunts around town with no problems. I had been
driving for twenty minutes or so and started down the freeway, after
about 5 minutes the check engine light came on. I came to a stop and
the engine started to idle roughly, like it was struggling to stay
going. I tried to accelerate from stop and the engine died. After that
I tried to start it 6 or 7 times. Each time the engine would start and
idle okay, but as soon as i pressed the accelerator the engine would
die. I tried gentle acceleration and revving it high in nuetral then
popping it quickly into drive. Each time the engine died. I let the car
sit for 30 minutes, started again, and got the same result.

I called a tow truck, which took about 45 minutes and towed it into the
shop. By the time I got it into the shop, the car basically ran fine.
The shop checked the OBDII codes and found: Knock Sensor and O2 Sensor.
I also found there were recalls for alternator and throttle body
issues, so I took it into the dealer. Neither one was defective
(according to them.) After all this, the car ran perfectly again, with
no check engine light, and I was able to drive around town for a few
days without incident.

Incident 2:
After a few days, I changed the air filter and filled up with premium
gas. Everything was running perfectly for about 30 minutes. Once again
the check engine light came on on the highway. I noticed that when I
would slow down, I got the same chugging, low idle behavior. I
continued to drive and hit some hilly sections of the highway. I
noticed that when I tried to accelerate up the hills, I would push the
peddle to the floor but the engine had very little power. After a few
seconds, the engine would "catch" and normal power would resume. During
this time, the check engine light would come on and off again
eratically. A few miles later, I got off the highway and came to a
stop. The engine chugged and died. I tried starting it a few times, but
was unable to keep the engine going. White / Blue smoke was coming from
the exhaust and there was a serious smell of gas.

I let the car sit for about an hour and tried it again...same behavior:
chugging engine, white smoke, strong smell of gas. The check engine
light was blinking as I tried to start it. I called another tow truck,
which took about 2 hours to get into the shop. By the time I got there
and started it again, there was still smoke coming from the exhaust and
the check engine light was on, but the car had noticeably improved. By
the time the shop looked at it, everything ran fine, there was no
smoke, the check engine light was off, and there were no codes.

Has anyone seen behavior like this before? The mechanic told me flat
out that he is totally confused by the problem and thinks it could be
related to the Knock Sensor, Air Flow Meter, O2 sensor, or Coolant
Sensor...I don't know even how to diagnose it, let alone fix it,
because the only way to make it happen is to drive long enough away
from home to the point that I have to tow it back.

I read online about a specific knock sensor problem that causes
hesitation, and I think this could have something to do with it, but
every piece of advice seems to be about Gary's Fix: a home built
electrical work-around that de-sensitizes the knock sensor, but I can't
find any info on it except for an outdated web page. Does anyone know
what he did?


Please, please help me!!!

Incidentally, we were supposed to drive the car up to portland this
weekend but we can't move, because we can't drive it more than a few
miles.

THANKS

On the white smoke issue, which doesn't fit well with the rest of the
symptoms... is the Subie consuming coolant, or does the coolant level return
to the same point after each episode? You may have to make a point of
marking the level and rechecking it.

My concern is that the head gasket(s) may be failing at freeway speeds and
the white smoke is from coolant. If so, the white smoke will have a sweet
smell. The usual shadetree test - with the engine cold, remove the radiator
cap, start the engine, pinch off the hose to the reservoir and place the
palm of your hand over the radiator opening to feel for rising pressure -
may not be definitive when the symptoms show up when hot. But if the test is
positive (boo!) you should focus on that until the head gasket question is
resolved. A failing head gasket can certainly cause the running problems.

Mike

 

[Kyle.Mack]

On the white smoke issue, which doesn't fit well with the rest of the
symptoms... is the Subie consuming coolant, or does the coolant level return
to the same point after each episode? You may have to make a point of
marking the level and rechecking it.

My concern is that the head gasket(s) may be failing at freeway speeds and
the white smoke is from coolant. If so, the white smoke will have a sweet
smell. The usual shadetree test - with the engine cold, remove the radiator
cap, start the engine, pinch off the hose to the reservoir and place the
palm of your hand over the radiator opening to feel for rising pressure -
may not be definitive when the symptoms show up when hot. But if the test is
positive (boo!) you should focus on that until the head gasket question is
resolved. A failing head gasket can certainly cause the running problems.

Mike

Thanks for the response. A couple other people had suggested head
gasket. I am leaning against this as the cause (it might be wishful
thinking). The white smoke has a very strong gas smell, and the tail
pipe seems to drip a bit of gas if I push the accelerator hard. I
smelled the drips of fluid coming from the tail pipe, and they smelled
like gas. No sweet smell. Coolant level seems exactly okay.

 

[Carl 1 Lucky Texan]

Thanks for the response. A couple other people had suggested head
gasket. I am leaning against this as the cause (it might be wishful
thinking). The white smoke has a very strong gas smell, and the tail
pipe seems to drip a bit of gas if I push the accelerator hard. I
smelled the drips of fluid coming from the tail pipe, and they smelled
like gas. No sweet smell. Coolant level seems exactly okay.

You are running very rich - that points to the temp sensor, MAF O2 or
other emmisions-type sensor. I suppose an injector could be stuck open
or some other esoteric/rare issue could do this too.

Carl

 

[Michael Pardee]

Thanks for the response. A couple other people had suggested head
gasket. I am leaning against this as the cause (it might be wishful
thinking). The white smoke has a very strong gas smell, and the tail
pipe seems to drip a bit of gas if I push the accelerator hard. I
smelled the drips of fluid coming from the tail pipe, and they smelled
like gas. No sweet smell. Coolant level seems exactly okay.

That would be a relief! At least it sounds okay so far. The sensor codes
don't explain the strong gas smell - even a completely wacked out O2 sensor
or knock sensor couldn't change the mixture that much.

Do you know if the spark plug color has been checked? I'm thinking of soot
to indicate the mixture was running way rich. If just one plug has signs of
soot I'd suspect the injector on that cylinder was jamming open... I haven't
heard of that happening but I'm sure it could. It would even be an
affordable fix

Mike

 

[Kyle.Mack]

That would be a relief! At least it sounds okay so far. The sensor codes
don't explain the strong gas smell - even a completely wacked out O2 sensor
or knock sensor couldn't change the mixture that much.

Do you know if the spark plug color has been checked? I'm thinking of soot
to indicate the mixture was running way rich. If just one plug has signs of
soot I'd suspect the injector on that cylinder was jamming open... I haven't
heard of that happening but I'm sure it could. It would even be an
affordable fix

Mike

So I am planning to replace the knock sensor, coolant temp sensor and
O2 sensor, but I am not sure which O2 sensor to replace. There are
two: one front and one rear. Which should I start with? BTW I am
looking to fix this issue, not necessarily get peak fuel economy.
Should I start with the front?

Thanks,

Kyle

 

[Carl 1 Lucky Texan]

So I am planning to replace the knock sensor, coolant temp sensor and
O2 sensor, but I am not sure which O2 sensor to replace. There are
two: one front and one rear. Which should I start with? BTW I am
looking to fix this issue, not necessarily get peak fuel economy.
Should I start with the front?

Thanks,

Kyle

I would, it almost always burns out before the rear one - it's hotter
and in front of the cat so gasses are somewhat more corrosive I guess.
Don't test with an ohmeter - it can destroy some of them. The voltage
drop across them should be between .5 and 1 volt IIRC (anyone?) and
should 'switch' which is why they are sometimes said to get 'lazy'.

Carl


Carl

 

[Michael Pardee]

I would, it almost always burns out before the rear one - it's hotter and
in front of the cat so gasses are somewhat more corrosive I guess. Don't
test with an ohmeter - it can destroy some of them. The voltage drop
across them should be between .5 and 1 volt IIRC (anyone?) and should
'switch' which is why they are sometimes said to get 'lazy'.

Carl

I also vote for the front sensor, whether or not it is related to your
original complaint. The rear one is just used to determine whether the
converter is working right, while the front one adjusts the mixture moment
by moment.

The O2 sensor is a fuel cell that produces about 0.9 volt when there is CO
in the exhaust and air on the outside of the sensor. When everything is
working right the output fluctuates between nearly 0 and about 0.9 volts
seven or more times per second (as in 3 1/2 cycles per second). I used to
have a link on that, but for general entertainment this will do:
http://users.cnnw.net/~fourty/sensors2.html

There is a controversy in alt.autos.honda as to whether an O2 sensor in an
OBDII system can get lazy enough to cause symptoms without setting the check
engine light. I have seen enough posts by credible people who say replacing
the O2 sensor has improved throttle response and/or fuel economy that I
think it may be true.

Mike