93 Subaru Impreza shuts down at idle

[bwv]

Hello. I own a 93 Impreza, auto trans, 94k (my mother in law gave it
to us last year, she had put 60K on it in 13 years).

Car runs great except for one thing that has recently developed.

There are some times when, if I am at a stop light, the car will
suddenly shut down. I can restart it, but will have to keep my foot
on the gas for it to stay on. Sometimes this shut down will happen if
I need to slow down during driving and take my foot off the gas to
brake.

A local mechanic who I trust checked the car's computer codes and did
not find any evidence of a failure of an idle- or air-flow-related
sensor.

This morning I checked the oil, and the dipstick showed I was about a
quart low.

Now I am beginning to think that there might be a low-oil sensor that
will shut down the engine if the pressure drops.

I added a quart and took her for a drive, and had no problems. That
could be coincidental.

If anyone has any thoughts or experience with this issue I'd
appreciate any information you could share. Thanks.

 

[Carl 1 Lucky Texan]

Hello. I own a 93 Impreza, auto trans, 94k (my mother in law gave it
to us last year, she had put 60K on it in 13 years).

Car runs great except for one thing that has recently developed.

There are some times when, if I am at a stop light, the car will
suddenly shut down. I can restart it, but will have to keep my foot
on the gas for it to stay on. Sometimes this shut down will happen if
I need to slow down during driving and take my foot off the gas to
brake.

A local mechanic who I trust checked the car's computer codes and did
not find any evidence of a failure of an idle- or air-flow-related
sensor.

This morning I checked the oil, and the dipstick showed I was about a
quart low.

Now I am beginning to think that there might be a low-oil sensor that
will shut down the engine if the pressure drops.

I added a quart and took her for a drive, and had no problems. That
could be coincidental.

If anyone has any thoughts or experience with this issue I'd
appreciate any information you could share. Thanks.

That's a puzzler with no codes. maybe something like cracked coil or
plug wires. Is the charging system working well? maybe check the voltage
at idle. Hmmm...is it more likleto happen when the car is hot or cold?

I dunno

Carl

 

[bwv]

That's a puzzler with no codes. maybe something like cracked coil or
plug wires. Is the charging system working well? maybe check the voltage
at idle. Hmmm...is it more likleto happen when the car is hot or cold?

I dunno

Carl

Those are excellent suggestions, thanks. The plug wires are all new,
as is the coil. I will check them out nevertheless. Charging system
seems fine,... the shutdown seems more likely to happen when car is
hot. I just hate to put in a $300 idle control sensor that may not
solve the problem. thanks again.

 

[Carl 1 Lucky Texan]

Those are excellent suggestions, thanks. The plug wires are all new,
as is the coil. I will check them out nevertheless. Charging system
seems fine,... the shutdown seems more likely to happen when car is
hot. I just hate to put in a $300 idle control sensor that may not
solve the problem. thanks again.

Well, sensors and the ECU are electronic components which can sometimes
be intermittent with temp.
Um...does it re-start and run immeditely after stalling? Ooops -
rereading the original post seems to indicate it does.

I dunno. I was gonna suggest crank angle sensor but...

maybe a good throttle body cleaning? The age of the car coupled with the
stresses low-mileage driving yields MAY mean some build-up of varnish
and other 'gunk' in a few systems. Probably wouldn't hurt to check the
PCV valve and hoses, but likely not connected to the problem.
But I THINK you must be careful not to use the wrong solvent in the
throttle body. I've read that some can damage a rubber seat or something
in there.

You should consider posting this at www.ultimatesubaru.org as well.

Carl

 

[johninKY]

Is your foot on the brake pedal when it stalls? Slim chance the brake
booster or check valve could be going south creating a major vacuum leak.

 

[AS]

How does the car die, does it shut off in a similiar way as when you
turn the ignition key to off or does it stumble, miss and then die.
Does it die at once or gradually?

I lean to think that there could be a vacuum leak, as suggested check
the EGR, booster, throttle body, IAC valve.

Good luck

 

[bwv]

How does the car die, does it shut off in a similiar way as when you
turn the ignition key to off or does it stumble, miss and then die.
Does it die at once or gradually?

I lean to think that there could be a vacuum leak, as suggested check
the EGR, booster, throttle body, IAC valve.

Good luck

Thank you all for the very helpful replies. First, I found the source
of the oil loss -- oil is leaking at the bottom of the timing belt
cover, where the two covers are bolted together. I know that there
should not be any oil in there, so I guess I have some sort of seal
problem. And the timing belt might be contaminated with oil, which I
suspect is not a good thing. I went ahead and changed the oil
yesterday, and the car is running fine -- no sudden shutdowns.

Looked inside the throttle body, looked clean, no sludge or carbon
buildup to speak of.

To answer the question, yes, the car usually would die if I took my
foot off the gas and applied the brake. Pressing the brake pedal
itself does not cause the problem, however.

When the car does die, it does so as if you are turning the key to the
off position, in other words, it is quite sudden -- no missing or
stumbling. If I act fast I can press the gas pedal and get it back
before it stops altogether, but this is rare.

Does anyone know of an online diagram showing the EGR valve location?
Thanks again.