Winter idling?

[YKhan]

The temperatures are falling around here. They're below zero Celsius
most evenings now. My car (2000 OBW) is in a heated garage, yet it
still seems to want to idle at high revs these days. It now starts out
at fast idle of 3000 rpm, and then settles down to slow idle of 2000
rpm, then after a bit of driving it might go down to 1500 rpm at idle.
Previously in the summer these things would be fast idle of 1500 rpm,
and slow idle just below 1000 rpm. What could be causing this
temperature-sensitive idling rate?

Spark plugs getting old maybe? I haven't changed them in a while. How
often do they need to be changed? The check-engine light doesn't come
on with these idle rates, BTW. So perhaps the computer thinks this is
normal?

Yousuf Khan

 

[M.J.]

The temperatures are falling around here. They're below zero Celsius
most evenings now. My car (2000 OBW) is in a heated garage, yet it
still seems to want to idle at high revs these days. It now starts out
at fast idle of 3000 rpm, and then settles down to slow idle of 2000
rpm, then after a bit of driving it might go down to 1500 rpm at idle.
Previously in the summer these things would be fast idle of 1500 rpm,
and slow idle just below 1000 rpm. What could be causing this
temperature-sensitive idling rate?

Spark plugs getting old maybe? I haven't changed them in a while. How
often do they need to be changed? The check-engine light doesn't come
on with these idle rates, BTW. So perhaps the computer thinks this is
normal?

I think regular spark plugs need to be changed every 30k miles.

I had crappy Champion plugs in my new '00 Impreza and replaced
them at approximately 26k miles with NGK Iridium plugs. Wow,
what a difference! Much, much, smoother running engine, and they
are supposed to last 60k or more.

You may check your oil if its not a bit too thick grade for winter
conditions. If so, adding a small amount of Marvel Mystery Oil,
just a few onces into the oil will thin it out and very likely affect/reduce
the idle, a bit.

M.J.

 

[M.J.]

I think regular spark plugs need to be changed every 30k miles.

I had crappy Champion plugs in my new '00 Impreza and replaced
them at approximately 26k miles with NGK Iridium plugs. Wow,
what a difference! Much, much, smoother running engine, and they
are supposed to last 60k or more.

Forgot to add that the idle went down a little, or so it seemed,
I was not really paying much attention to idle rpms per se, but
I think they went down.

You may check your oil if its not a bit too thick grade for winter
conditions. If so, adding a small amount of Marvel Mystery Oil,
just a few onces into the oil will thin it out and very likely
affect/reduce
the idle, a bit.

More precisely cold-start idle rpms.

M.J.

 

[Yousuf Khan]

Forgot to add that the idle went down a little, or so it seemed,
I was not really paying much attention to idle rpms per se, but
I think they went down.

How much more expensive are the Iridiums compared to regular?

More precisely cold-start idle rpms.

It turned out that the problem could be fixed by resetting the ECU.
However, it's true that I haven't changed the sparks in a very long
time. I've changed the air filters, the oil, the fuel filters, etc.,
many times, but the sparks get ignored.

Yousuf Khan

 

[M.J.]

How much more expensive are the Iridiums compared to regular?

They are several times more expensive. I forget how much I paid for mine,
USD $9.99 a piece, or so. Taking into account that it is a somewhat
unpleasant
job to change plugs in a Subaru flat-four engine, I consider it money well
spent,
as I won't have to do it again for a very long time. The smoother running
engine
is an extra bonus. They claim the Iridiums also save fuel but I haven't
been
able to notice much difference.

I highly recommend the NGK brand.

It turned out that the problem could be fixed by resetting the ECU.

Good to know.

M.J.

 

[YKhan]

USD $9.99 a piece, or so. Taking into account that it is a somewhat
unpleasant
job to change plugs in a Subaru flat-four engine, I consider it money well
spent,
as I won't have to do it again for a very long time. The smoother running
engine
is an extra bonus. They claim the Iridiums also save fuel but I haven't
been
able to notice much difference.

I highly recommend the NGK brand.

Yeah, so I went down to a couple of Canadian Tire stores yesterday to
check out the spark plugs. One of the stores was completely sold out of
Iridiums, and the other store had them, but the particular model that
is relevant to my model had only one pair available. The price was
$19.99 for a package of two. Plus some kind of a 3 year guarantee?
What's that guarantee about?

Also noticed that the Iridiums were of similar shape and design to the
bunch of cheaper Platinum tipped plugs. Basically they all seem to have
that extra narrow point on them. I assume the only difference is that
the Iridiums last longer than the platinums?

Also I don't have a torque wrench, is it advisable to put a spark plug
on without a precise torque wrench? The owner's manual says I should
let the dealership change the plugs on this engine.

Yousuf Khan

 

[M.J.]

Yeah, so I went down to a couple of Canadian Tire stores yesterday to
check out the spark plugs. One of the stores was completely sold out of
Iridiums, and the other store had them, but the particular model that
is relevant to my model had only one pair available. The price was
$19.99 for a package of two. Plus some kind of a 3 year guarantee?
What's that guarantee about?

Also noticed that the Iridiums were of similar shape and design to the
bunch of cheaper Platinum tipped plugs. Basically they all seem to have
that extra narrow point on them. I assume the only difference is that
the Iridiums last longer than the platinums?

Supposedly they are better, not necessarily last longer than platinums.

I think they may, at least partially, pay for themselves in fuel savings.
This is difficult to observe on a single tank of gas, but over 30k, or 50k
miles there may be a good number of gallons of fuel saved.

Here's NGK site where the describe them and also have a nice tech
section giving some very general instalation tips and other info.

http://www.ngksparkplugs.com/products/cars_trucks_suvs/iridiumix.asp?nav=11420&country=US

Also I don't have a torque wrench, is it advisable to put a spark plug
on without a precise torque wrench? The owner's manual says I should
let the dealership change the plugs on this engine.

Changing spark plugs on a Subaru can be tricky. If you are not
very patient, or somewhat mechanically inclined, you may well
let the dealer install them just like the owners manual suggests.

This is beacause the access is not very good, and primarily because
there is a visibility problem. The plugs sit so deep in engine block
you barely see them. This can be a bit intimidating. If you get
aggravated easily let the dealer do it. Don't get me wrong it can be
a do-it-yourself job, just if you are patient, don't panick, and are
at least minimally mechanically inclined. Do a google search of this
newsgroup, there was a guy describing here how he uses plastic
tubing as an extention when positioning plugs into the deeply
recessed plug holes.

I don't use a torque wrench, and I never had a problem.
Remember to use anti-seize compound and do not tighten
them "too much." With anti-seize compound on they tend to
slip in very nicely and overtightening is a risk.

M.J.