Hi all,

I'm in line for my next outback...my other one pretty much completely spent after 100,000 miles with serious torque bind and completely shot struts/ shocks. It's headed for the boneyard to get pieced out to build other subies for worthy drivers.

 

I test drove the new one...a '98 standard with about 125,000 miles on it. It sounded fine except for a mild backfire/sputter when letting of the gas to shift gears (especially from the lowest gears when RPM is the highest).

 

 

Is this something I should be concerned about? I'm thinking plugs/wires...maybe fuel or air filter?

 

Thanks for your input,

Damien

Probably a leak in the exhaust, or the cat is gutted. Any CEL on?

 

Honestly I wouldn't worry about it unless you notice the gas mileage is really bad or have other driveability issues.

I heard years ago, that slight backfire on cars in general can result from a bad exhaust valve. I don't know if this applies to Subies, but I thought I would at least mention it.

well I suppose it could be the timing belt....maybe a tooth or two off.

 

 

I suppose it could also be carbon buildup on the valves....

 

whaddyathink?

 

 

--Damien

there's no CEL light on...

Yeah timing is easy to check. An exhuast cam off a tooth might do something like that.

A burned valve will generally cause a misfire (unless a very minor case), and show a loss in compression on the cylinder with the burned valve.

well then I'm hoping it's just carbon scoring...a dose of 'Seafoam' in the tank may be the solution....(or maybe the trickier pouring a quantity down the PCV inlet).

 

 

What are symptoms of an improperly aligned timing belt?

 

 

Cheers!

--Damien

are you 100% sure it is an actual backfire? or could it be just exhaust pop sounding loud due to a hole in the exhaust/loose exhaust header or blown exhaust gasket???

 

i run a cherry bomb turbo style muffler on my Legacy and when i downshift and back off the throttle to slow down it pops pretty good - I actually like it!

yeah, maybe...it's more prevalent if there's an increased weight load on the vehicly.

 

I'll listen more closely as I rarely get a look at the undercarriage....

 

 

 

You lucky guys with shops'n'lifts'n'tools... *sigh*

 

 

--Damien

yeah, maybe...it's more prevalent if there's an increased weight load on the vehicly.

 

I'll listen more closely as I rarely get a look at the undercarriage....

 

 

 

You lucky guys with shops'n'lifts'n'tools... *sigh*

 

 

--Damien

 

tools - yes

shop - well, sort of - cram packed garage that i cant get the complete car into...

Lift - yeah, in my dreams!

if it's popping when engine braking that is pretty normal. I love it when my car does it! I still get a bum bum sound when I rev and let off.

I noticed that the part of the air intake assy (the tube with the MAF sensor) was not properly clamped to the filter housing so that may have been a contributing factor. I put in a new Subaru filter anyway...

 

could be dirty valves...I guess I'll have to drive it for a few more thousand miles with the fuel additives in the tank and see if that reduces the possible carbon buildup on the valves.

 

I'll let ya know.

 

 

--Damien

The ever ignored but simple vacume gauge, sees all tells all.

 

http://www.classictruckshop.com/clubs/earlyburbs/projects/vac/uum.htm

Carbon on your exhaust valves will not be cleared off by fuel system cleaners, the cleaner is already burned by the time it gets to the exhaust valve.

Fuel system cleaners clean intake valves, because the fuel is sprayed over the face of the valve by the injectors.

Heat cleans exhaust valves. Engine heat burns the carbon off.

Try driving the car hard if it is not too bad that may help.

 

Using a water spray into a vacume line or air intake (spray bottle) can decarbonize an engine, just do it in the middle of no where as it can make quite a lot of smoke. It does the same thing as any fancy chemical. Its the way it used to be done but modern engines dont carbon up unless driven too gently. Or sometimes things just happen.

Well the solution is to pour the stuff directly into the PCV inlet but I'm too weary to 'do it again'.

 

 

The Seafoam stuff really works...I used just a tiny bit for my lawnmower and it perked it right up.

 

 

My nose caught a whiff of jet fuel exhaust...so the secret may be therein.

 

 

--Damien