Subaru air filter. Is it needed?

I recently purchased a 7/98 Subaru Outback AWD Standard with a 2.5L engine. I noticed it is missing its air filter(engine, not cabin). It runs rough on start and idle and starting to drive. Once it gets moving, it seems to run smoothly with no power loss(of course I have no idea what kinda power it should have, I just purchased it).

Could it be that a air filter might be the answer? I don’t want to buy a filter if it doesn’t need one(read ‘cheap bastard’).



You’ll definately want an air filter. I would not drive the car without one. There is fair chance that the engine has already been damaged.

Yup, the air filter might be the answer.
Modern engines measure the airflow in as well as the manifold pressure, temperature, and a number of other variables, run them all through a computer, and meter the fuel based on the output of that formula. Change the airflow in for a given set of paramters by removing the air filter, for example, and you just may cause the metering to be off enough to affect the idle.

Try putting an a filter and see what happens. Post back with the results.

Without the $10 or less air filter, you are getting a bunch of dust, etc in your ocmbustion chamber. Get one in ASAP and see if the idle changes for the better. I am surprised you don’t have a check engine light on.

Did you buy a used car without getting it checked by your mechanic first, or did your mechanic not notice the missing air filter? I wonder how long this car has been running without an air filter. It could have significant damage.

As others have stated or implied, this does not bode well for some of the less obvious maintenance items that the previous owner decided to cheap out on. If you want this car to continue running, and to hopefully run better than it is currently, you need to open up that wallet and pony up the $10. for the air filter.

Just pray that the previous owner didn’t skip things like timing belt replacement, fuel filter replacement, differential oil change, etc. Even though it is a bit late, I would suggest a thorough inspection by your mechanic in order to catch any other “time bombs” left by the negligent previous owner. Although a mechanical inspection is unlikely to provide much information regarding the timing belt, I think you should be prepared to spend a few hundred $$ on the replacement of the timing belt and the water pump. Otherwise, your investment could quickly become a pile of immobile metal.

I would do the equivalent of the 60K or 120K service, including timing belt, unless there is proof otherwise. I found it really weird for no air filter to be there, and while I don’t normally check out that aspect of the car when shopping around, one can’t help but wonder what else may be missing or not done. Was the idle rough when you road tested it, or did that occur later?

Hopefully doing one of those services, plus timing belt, will get the car back into decent shape, maintenance-wise, without any negative occurrences.

No offense intended but sometimes cheap bastards can be penny wise and pound foolish. You should have had this used vehicle checked by a mechanic before you bought it. By spending a little up front, you can save yourself from buying a junker. Also, with a mechanics report in hand you possibly could have negotiated a better price.

Anyway, there’s no question you need an air filter, if only to prevent further damage.

I bought the car from a young woman. Need I say more? The car was also down on oil - a quart and a half. She mentioned her mechanic said it had a bad cylinder. I don’t know.

I put in the $7. air filter last night. I didn’t drive it, but I let it roughly idle for a few minutes. No real change.

The “Check Engine” light is flashing.

I have no idea how long she may have driven it without the filter.

Thanks for the replies.

The young woman may not have been diligent regarding maintenance, but you were apparently either too trusting or too interested in a bargain to do your due diligence prior to buying this car.

“The “Check Engine” light is flashing.”

When the CEL is flashing, that indicates a SERIOUS problem, and the car should be brought to a qualified mechanic immediately. Next time you buy a car, I strongly suggest that you have it inspected by your mechanic prior to purchase.

THE ANSWER is yes. The flashing CEL means there is a serious running issue. My simple stab is your MAF(Mass Air Flow Sensor) is contaminated and has failed and would translate to your poor running condition.

However the only way to get this checked out is the getting your codes read. You can pay a mechanic for diagnosis(includes code read) or possibly get code read free at an auto parts store. The free read is that, simply a code but you need to post back to get an interpretation. Don’t count on auto parts counter people to diagnose.

Driving around with a flashing CEL is likely damaging the engine.

Hope it was a cheap car, this likely won’t be cheap to fix.

Post back.

I’ll put it to you this way…

For every gallon of gas your car consumes…it will also consume 10,000 gallons of air. Do you want those 10,000 gallons of air filtered or unfiltered??

Excellent post. I never thought of it that way.

Hey, great info all.
The lady I bought the car from was younger than me and good looking. I didn’t ask a single question before I handed over the five C-notes.
The car is in great shape and I think I did all right even if I have to spend another ten C-notes to put it on the road. Am I looking at more than that if the engine is really toast?
I plan on taking it to a dealer to have them diagnose and give it a once-over. Do they charge for that?
Even if it is only running on three of the four cylinders(like she said it was), it should still be less costly to drive than my V-8 Ford. Will the unburned fuel end up exploding my muffler?

Not meaning to come across as too crass here but you bought a rough running 10 year old vehicle with the CEL illuminated, told by the seller it had a cylinder down on it, and you coughed up 500 bucks anyway?
Sorry, but with those conditions the car is 100-200 bucks at best. And that’s if one really, really wanted it and was mechanically inclined on top of that.

Given the fact a mechanic has said a cylinder is down and the engine is a quart and a half low on oil it’s entirely possible this car was seriously overheated by the seller. Her mechanic gave her the grim news and she decided to dump the car rather than spend a lot of money on it.

No air filter? Excessive blow-by caused by fried piston rings could have caused the air filter to become saturated with oil and the seller’s mechanic simply removed it.

Your first step should be to remove the spark plugs and run a compression test. If the results are bad, as I fully expect them to be, then the engine is going to have to be rebuilt or replaced.

You are better off finding a good independent mechanic to get the CEL code read, compression test and any follow-on work done. You will get charge for the labor. Follow ok4450’s advice below and I would be checking out low mileage used engines for this car.

I sort of wish the details that were added later were in the original post. It definitely would have changed my answer.

To the OP, I think the only way you’ll get out for a mere 10 C-notes is to look for a boneyard engine to replace the original. That would be my suggestion.

Sincere best. You’ve gambled, and frankly. with a bit of luck you still may come out ahead.

Hey! The Governor made me do it.

Here’s how I see it:

Girl gets her $ and is happy.
I get a loaded car that’s in mint shape(excluding under the hood of course;) that runs well enough to get me to work and back and I am happy.
And… if I ever see fit to fix it, the repair facility gets money from me and is happy.

Happy! Happy! Happy!

Oh, I can sell the car to a scrap metal yard for $400. At least I had fun tinkering on the thing for a while and it only cost me $100!

Thanks for the replies and all the helpful info!

I’ve read all your replies and have to add that I own a subaru outback and you have got a real good car. So put the money into it to have these things checked out because they are actually pretty simple fixes. You will not be dissappointed in your ride.

Thanks. That’s what I think too.

If I was to spend all the time checking out a used car before buying it, like some here think I should have, it would be gone by the time I was ready to buy. And if I did get to buy it, I would really be upset when something went wrong later.

This way I might end up pleasantly surprised!