2007 Impreza stops for no reason

[blank]

Driving along the highway and the car just stops for no known reason. It
happened three times on a long trip recently. Had cruise control turned on
at the time but this might be just a red herring. Can put it into neutral
while still moving and turn the key and it restarts. Have had intermittent
trouble with this vehicle since new--sometimes it just wont start. Grind
and grind away at it and it goes. I think it is some sort of electrical
problem but am just guessing. Any thoughts?

 

[JD]

Driving along the highway and the car just stops for no known reason. It
happened three times on a long trip recently. Had cruise control turned
on at the time but this might be just a red herring. Can put it into
neutral while still moving and turn the key and it restarts. Have had
intermittent trouble with this vehicle since new--sometimes it just wont
start. Grind and grind away at it and it goes. I think it is some sort
of electrical problem but am just guessing. Any thoughts?

I'd look at the ignition module. Intermittent faults are notoriously hard
to diagnose.

 

[blank]

I'd look at the ignition module. Intermittent faults are notoriously hard
to diagnose.

Yes, I can imagine that it is going to be more or less impossible to find.
If the fault is not showing how can a mechanic know what to fix? I guess we
will just have to live with it, but its a real disappointment--it means we
need to change our thinking and realise that we can not consider the car to
be reliable. Damn.

 

[JD]

Yes, I can imagine that it is going to be more or less impossible to find.
If the fault is not showing how can a mechanic know what to fix? I guess
we will just have to live with it, but its a real disappointment--it means
we need to change our thinking and realise that we can not consider the
car to be reliable. Damn.

There are a few things you can try that aren't expensive. I would change
the plug wires, and check the connections to the ignition module, including
the ground. They can test the ignition modules. Also, does the car throw a
code when it happens?

 

[blank]

There are a few things you can try that aren't expensive. I would change
the plug wires, and check the connections to the ignition module,
including the ground. They can test the ignition modules. Also, does the
car throw a code when it happens?

I wasnt aware of any code display. Didnt notice anything at the time. But
we were so freaked out by it happening that I could have missed it.
On one occasioin we were in very hilly singlelane each way conditions out in
the middle of nowhere in the region of Mt Isa, and I knew there was a huge
roadtrain close behind me because I'd just passed it, and the bloody thing
concked out. I nearly shat myself. Anyway got it going again before being
crushed by the roadtrain. If my wife had been driving at the time it might
have been a very different story.

OK, so where does the code show up? When they test the ignition modules
would an intermittent fault like this be diagnosed? Appreciate any comments
before I take it to Subaru.

 

[S]

Hi Blank!

Driving along the highway and the car just stops for no known reason. It
happened three times on a long trip recently. Had cruise control turned on
at the time but this might be just a red herring. Can put it into neutral
while still moving and turn the key and it restarts. Have had intermittent
trouble with this vehicle since new--sometimes it just wont start. Grind
and grind away at it and it goes. I think it is some sort of electrical
problem but am just guessing. Any thoughts?

'07 car is (should be, anyway) still under factory warranty. I'd take
it back to the dealership and make it _their_ problem.

On a vehicle this new, the most likely candidate IMO is an
intermittent in the wiring harness.

Start the car, stand on your head so that you can reach up behind the
dash, and start moving wires around. Pay particular attention to the
large bundle(s) that terminate at connectors thru the fire wall. When
you move the bundle that has an intermittent. in all probability the
engine will hiccup, or stall. Spread the wire bundle and start again,
moving individual wires until you find _the one_.

My reasoning is this:

When the wiring harness is assembled, the connector male and female
pins are first crimped onto the prepared wire ends, and then the pins
are inserted into the plastic connector blocks. There is a metal tab
on the pin that locks it into the connector block once it is inserted
far enough.

It sometimes happens that, either because one wire is a tiny bit too
short, or due to sloppy workmanship, one pin doesn't get "locked" into
place. When the connectors are subsequently mated, the loose pin is
pushed back in the block w/o making a secure connection. Normal
vibration and/or temperature cycling can then result in an
intermittent contact.

FWIW, this can be a major PITA to find, but is easy to fix once you
find it; just push the wire/pin in 'til it locks. The wrench at the
dealership _should_ know this, and know how to deal with it. Again,
I'd make it their problem.

Hope this is helpful.

ByeBye! S.


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

 

[JD]

I wasnt aware of any code display. Didnt notice anything at the time.
But we were so freaked out by it happening that I could have missed it.
On one occasioin we were in very hilly singlelane each way conditions out
in the middle of nowhere in the region of Mt Isa, and I knew there was a
huge roadtrain close behind me because I'd just passed it, and the bloody
thing concked out. I nearly shat myself. Anyway got it going again
before being crushed by the roadtrain. If my wife had been driving at the
time it might have been a very different story.

OK, so where does the code show up? When they test the ignition modules
would an intermittent fault like this be diagnosed? Appreciate any
comments before I take it to Subaru.

You would need to have the ECU scanned. There may be pending codes that
wouldn't light the MIL light. That is the code I am referring to.

If they check the ignition modules, it may show up if the module is weak.
Maybe not though. As I said; intermittent faults are hit an miss.

 

[1 Lucky Texan]

"blank" <nowhere.net> wrote in message









You would need to have the ECU scanned.  There may be pending codes that
wouldn't light the MIL light.  That is the code I am referring to.

If they check the ignition modules, it may show up if the module is weak.
Maybe not though.  As I said; intermittent faults are hit an miss.

Yeah if there is no meaningful code stored (I might discount some
generic misfire code - dunno) I'd strongly suspect the ECU. Seems to
me an intermittent from any sensor would throw a code pointing to a
wiring or sensor issue. No repeatable/meaningful code - probably means
the ECU itself is shutting things down. And I would have a serious
discussion with the dealership and/or a regional Subaru Rep. I think
I'd begin documenting everything too.