mwatt

I don't have a direct answer to your concern, but did you read the post by "Forester air recirculation problem" ??dalecherokee It is worth noting that you're the second owner to post an "exhaust odor inside vehicle" concern within a week.......although you mention yours occurs in the "outside air" mode.... Is the exhaust system on your vehicle damaged/modified in any way? Has the vehicle been put up on a lift by a technician to have the exhaust system inspected? Have you looked at the tailgate and tailgate surround weatherstrip (as I suggested to dalecherokee) to make sure the gate closes/seals securely so that exhaust isn't sucked back into the interior? A leaking manifold gasket can be HEARD, especially under acceleration. Starts out as a "ticking" under acceleration..........

prices on parts at any dealer (not just Subaru stores) depend on the parts pricing "matrix" that the parts manager has employed for "over-the counter" parts sales. Typically, small parts (like valve cover bolt seal washers, for example) that cost the dealer only a little are marked up the MOST, so they make the best profit. Many dealers will apply a particular parts matrix to groups of parts that they consider "fast movers", again to maximize their profit. As you're probably well aware, all of this pricing matrix stuff can vary tremendously from dealer-to-dealer. I bought twelve valve cover bolt washers (13271AA051) from a dealer here in MD for 3.10 each; dealer cost is 1.77 each and Subaru LIST is 2.95 each. Have you checked other dealers in your area? Dealers in urban areas tend to be worse about this because they often have a "captive audience" business ethic (or lack thereof).

when you press the recirc button, you should hear air "rushing" under the passenger side of the dash, below the glove compartment (if system is working properly). By the way, you're not using "recirc" unless the A/C is on, right? (Using "recirc" with the compressor off allows excessive moisture to build up inside the vehicle and will lead to window fogging.) Also---does the liftgate latch securely? Is the liftgate opening surround weatherstrip damaged in any way (Thereby allowing your vehicle's exhaust to be sucked inside...)?

Thanks... now I understand the abbreviation. I was a service advisor at a Chevrolet dealer for years (that's why I own a Subaru) so I was used to seeing the letters "AF" applied to mass air flow sensor.

How did you diagnose mass air flow sensor with no code stored?

Thank you for the great advice--after I read more about knock sensor issues posted by other owners, I think you've probably pointed me in the right direction. The possibility of the knock sensor causing timing-retard when it shouldn't makes sense because if I deliberately hold the throttle at about 1100 RPM in "D", I can replicate a continuous "up and down" surge, although it's rather subtle. I'll let you know what I come up with....thanks again.

My 1999 Legacy GT 2.5 (Automatic--115,000 mi) runs great with one exception: when the engine is fully warm in traffic and the throttle is pressed very gently(just enough to edge the vehicle forward in traffic), the engine "stumbles" or surges. If you step on the accelerator normally, like accelerating away from a stop sign, the engine responds properly. It's not an engine misfire--just a momentary stumble at about 1100 RPM when the accelerator is pressed very gently from a standstill. I've removed the throttle body, cleaned it out, and replaced the T/B gasket. I replaced spark plugs and plug wires as normal maintenance just a few months ago, but that was not an effort to correct the stumble condition. The "check engine" light is NOT coming on--I borrowed a friend's Snap-On scanner and there are no codes stored. Anyone have any ideas?