98 Subaru Forrester Stalls with in 10 seconds of start up

[timmiller4]

We had the oil changed on our 98 Subaru Forrester recently. We got the
car back and tried to start it up, it started fine but with in 10
seconds or so it would start running rough then stall. If you hit the
gas the engine revved fine and didn't show any signs of roughness,, but
if you let it idle it would stall out. We had it towed to a mechanic
and he said he got some error codes off of it saying that there was an
error in the NOX sensor and the Evap System and that the NOX sensor is
the likley culpriate. I always thought the NOX sensor was there to
measure emissions levels and I can't see how it could be causing this
type of problem. Am I wrong and a NOX sensor could cause this type of
problem?

Tim

 

[Carl 1 Lucky Texan]

We had the oil changed on our 98 Subaru Forrester recently. We got the
car back and tried to start it up, it started fine but with in 10
seconds or so it would start running rough then stall. If you hit the
gas the engine revved fine and didn't show any signs of roughness,, but
if you let it idle it would stall out. We had it towed to a mechanic
and he said he got some error codes off of it saying that there was an
error in the NOX sensor and the Evap System and that the NOX sensor is
the likley culpriate. I always thought the NOX sensor was there to
measure emissions levels and I can't see how it could be causing this
type of problem. Am I wrong and a NOX sensor could cause this type of
problem?

Tim

Was ANY other service done?(air filter for instance) Is the check engine
light on? Do you know the exact code number the mech got?

Carl

 

[Porgy Tirebiter]

We had the oil changed on our 98 Subaru Forrester recently. We got the
car back and tried to start it up, it started fine but with in 10
seconds or so it would start running rough then stall. If you hit the
gas the engine revved fine and didn't show any signs of roughness,, but
if you let it idle it would stall out. We had it towed to a mechanic
and he said he got some error codes off of it saying that there was an
error in the NOX sensor and the Evap System and that the NOX sensor is
the likley culpriate. I always thought the NOX sensor was there to
measure emissions levels and I can't see how it could be causing this
type of problem. Am I wrong and a NOX sensor could cause this type of
problem?

Tim

Tim.....
This is just one of the reasons "JiffyBoob"/ "Pit-Stop" and some of the
others are a BAD idea .....
Others have had wrong fluids installed, oil drain plugs stripped out,
filters crossthreaded.
A few have had the tranny drained and the engine overfilled!
Batteries filled with TAP WATER, brake fluid contaminated and/or wrong
type....

I suspect they broke a connector, unplugged something or?? while in/under
there.

Good luck!

 

[Dmitriy]

Do you mean the 'knock' sensor by any chance? A bad one of those can
put your car in 'limp' mode... it still shouldn't stall out though.

The only sensor that really actually matters is the oxygen sensor (or a
possibly a MAF, since you have a 98 Forester, and I think those were
MAF) in your intake.

Ask the mechanic what the actual codes were (i.e. number, like P1234),
and post them here.

 

[timmiller4]

Here's an update on the situation. The mechanic looked at everything
that could have been screwed up during an oil change and didn't find
anything that could be causing this problem. After talking to him
further said that he really didn't think the NOX (knock?) sensor was
the problem. The mechanic also said that he had managed to get it
running but it was real rough and it backfired on him once. Based on
that he suggested that a better place to start was with the
plugs/wires. As I was planning on having it "winterized" anyway I told
him to go ahead and give it a tune up as well. I'm hoping to hear back
sometime today on whether or not that worked.

To answer a few questions:

1) I don't have the error codes, I'll see if I can find out what they
are. The mechanic did say that it looks more like they are the result
of the engine running rough and not the cause

2)The place that did the oil change did "check" the air filter. They
told us that it was fine and didn't need to be replaced.

3) They probably said "knock" (as that makes more sense) and I heard
"NOX". I'll make sure to get that clarified.

 

[Edward Hayes]

I'm still not convinced that there is a connector loose or not
connected.

 

[Dmitriy]

The codes could help us diagnose the problem... even if they are the
effect and not the cause.

The wires/spark plugs would indeed cause the car to run rough, but it
would not cause repeatedly sputter and die exactly 10 seconds after...
you car would either not run, or run crappy all the time.

Sounds more like something ECU related... meaning that (and I'm not an
expert on Subaru ECUs so I'm just giving you my idea on how it works)
when you start the car, for 10 seconds or so the ECU will keep it in
"startup" mode, then after 10 seconds it goes into another mode... and
that's when it stalls. Since it's not very likely that the ECU itself
went bad, I would agree that it's some kind of sensor, maybe the MAF.

Or... it may be something fuel related, for example it may be a bad
fuel pump.

It's really hard to tell without knowing more information (namely the
codes...)

Try also searching the forums at nasioc.com

 

[Carl 1 Lucky Texan]

Here's an update on the situation. The mechanic looked at everything
that could have been screwed up during an oil change and didn't find
anything that could be causing this problem. After talking to him
further said that he really didn't think the NOX (knock?) sensor was
the problem. The mechanic also said that he had managed to get it
running but it was real rough and it backfired on him once. Based on
that he suggested that a better place to start was with the
plugs/wires. As I was planning on having it "winterized" anyway I told
him to go ahead and give it a tune up as well. I'm hoping to hear back
sometime today on whether or not that worked.

To answer a few questions:

1) I don't have the error codes, I'll see if I can find out what they
are. The mechanic did say that it looks more like they are the result
of the engine running rough and not the cause

2)The place that did the oil change did "check" the air filter. They
told us that it was fine and didn't need to be replaced.

3) They probably said "knock" (as that makes more sense) and I heard
"NOX". I'll make sure to get that clarified.

WEll, its somewhat common on some soobs to fail to clip in the bottom
section of the air filter box - though your mech likely would have
spotted that.

maybe something just coincidently happened like the belt slipped time -
that could possibly yield backfiring. Or some kind issue with an
injector stuck open ore something?

weird


Carl

 

[VP]

Here's an update on the situation. The mechanic looked at everything
that could have been screwed up during an oil change and didn't find
anything that could be causing this problem. After talking to him
further said that he really didn't think the NOX (knock?) sensor was
the problem. The mechanic also said that he had managed to get it
running but it was real rough and it backfired on him once. Based on
that he suggested that a better place to start was with the
plugs/wires. As I was planning on having it "winterized" anyway I told
him to go ahead and give it a tune up as well. I'm hoping to hear back
sometime today on whether or not that worked.

To answer a few questions:

1) I don't have the error codes, I'll see if I can find out what they
are. The mechanic did say that it looks more like they are the result
of the engine running rough and not the cause

2)The place that did the oil change did "check" the air filter. They
told us that it was fine and didn't need to be replaced.

3) They probably said "knock" (as that makes more sense) and I heard
"NOX". I'll make sure to get that clarified.

I vaguely remember that someone had mentioned this kind of symptoms
when the air filter was replaced and airflow sensor (which is located
somewhere in the vicinity of air filter box) was left disconnected.
The symptoms seem typical for Mass Air Flow (MAF) Sensor Failure
http://www.ecutek.com/tuning/diagnostics/

 

[timmiller4]

Just wanted to let everyone know that the problem was resolved. They
performed a full tune up and it is now starting and running fine. It
looks like it was indeed a knock sensor that was causing the error
code. The tech said a couple of the plugs were really fouled and the
gas filter was very dirty. So it looks like nothing was caused by the
oil change and that it was just a coincidence. Thank you to everyone
who participated in this discussion.

Tim