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Conflicting Diagnosis: 2004 Subaru Outback Question


Apologies in advance for the long post: My spouse and I are the original owners of a 2004 Subaru Outback. The car was rock-solid reliable and judiciously maintained by us through ~165K. Then we moved to a new area and had to deal with a new mechanic and a new dealer — at which point things became complicated.

I’ll start with my question and then back into the explanation: Is it possible for a Subaru Outback 2.0L, AT (EJ259, CA engine type) to throw a P1092 code?

We’re stuck between two conflicting diagnosis: An independent repair shop claimed that this code is for a tumble generator valve in a Subaru WRX. The shop owner says we need to install a new electronic control module because that part doesn’t exist on our Outback engine. Our local Subaru dealer has a completely different take. In February, before pandemic lockdowns were in effect, the dealer claimed to have attempted to install what the service advisor called a “tumble generator valve”. They apparently broke the replacement part — an “AY Motor Assembly” per its actual part name — so they took it off and reinstalled our old one. They then ordered a replacement and claimed that upon installing it, the CEL did not clear. At that point, the dealer diagnosis became a “dirty intake manifold” — but they do not guarantee that cleaning the manifold will correct the problem!

Shortly after the dealer advised us to clean the intake manifold, the pandemic lockdowns struck and they abruptly told us to take our car back. In July we attempted to pick up where we left off. Some five weeks at the independent mechanic’s shop later, the shop owner was still reporting he was unable to source the part (a used ECM). In August, we were evacuated for a wildfire — at which point we called and asked “When?”. Without even pausing to apologize for the delays, the owner of the shop simply told us to come get our (still not repaired!) car. Since the next nearest Subaru dealer is ~80 miles away, spouse decided to approach dealer management about what we hoped had been a fluke (our first experience with this particular dealer since moving to the area). We learned that the service manager we were dealing with back in February had been let go and were hopeful that the car would be properly diagnosed after the current service manager claimed he would take care of us. That was a month ago and now we’re right back to square one — calls to the service manager routed directly to voicemail, with no clarification on whether the P1092 code was relevant to our car or whether or not cleaning the intake manifold would be guaranteed (our service tickets earlier this year actually say they won’t guarantee the repair).

Although we wanted to hit the 200K odometer mark with this car, we threw in the towel and bought another car while evacuated from a recent wildfire. Because the car was still tied up in the shop — some 9 weeks between the independent shop and the Subaru dealer so far this year — we were unable to trade it in. It’s due for a smog check but in CA a check-engine light for any reason precludes a smog check. We’ve poured too much money into this car within the past year — head gasket repair and a slew of suspension repairs that inexplicably became necessary while in the care of the same independent mechanic — to junk this car. Ideally, we’d like to donate the car to someone who can use it — assuming there’s any hope of fixing it without throwing another $800 into it. Any suggestions?

I was a little fuzzy about what was called a tumble generator valve as I’ve never heard the phrase around here. After a quick look I see it’s nothing more than an intake manifold runner and the 1092 code is for a left hand stuck open. It’s quite possible that it’s stuck because of intake deposits over the years and a little cleaning could unstick it. In the event a new runner is needed I don’t think they’re very much in the aftermarket.

Just an FYI, but the purpose of the intake runners is to provide long runners at low RPMs and which helps performance. When the RPMs get up to 4k or so the system changes over to short runners by flap movement and that aids performance at higher RPMs.
One used to see this half a century ago on some Chrysler products. They had Short Ram and Long Ram intake manifolds available.

Cars are perfectly driveable with inoperative runners but that will likely be a problem in CA due to DTCs being set.

I had a driver side runner sticking on my Lincoln some years back and managed to free it up with some aerosol carburetor cleaner. Good thing because for some weird-oh reason no one provides intake runners for a 96 Lincoln. One can get them for 95s and 97s though.

Thanks for the reply. If I had to guess, the valve/flap may have stuck closed because the car can’t climb any sort of grade or get up to highway speed.

It strikes me as odd that the dealer had this vicinity open to install the “Motor AY Intake Manifold”, which they say they broke, after which they said they tried again to replace that same part (check engine light was still on so they pulled it and reinstalled the old one). Between the head gasket work last year and the dealer service, no one noticed that it needed to be cleaned earlier? Hmm… (Dealer wants $800 to clean the manifold but shop that did the prior work still stands by their faulty ECM diagnosis.)

The shop we used for the head gasket work last summer and to repair the shorted headlight assembly either had very bad luck with our car or was dishonest (took us to the cleaners). The first HG repair failed immediately, bending valves (re-do of the job was under warranty). When the car was supposed to be ready for pickup, we learned the rack-and-pinion is leaking (to the point of fluid accumulating in the exhaust and rising up through the engine bay as smoke — not something that had occurred prior to the HG work). When the rack-and-pinion was repaired, we took it on a test drive only to find we couldn’t make a turn without the car shaking/quaking (formerly it had no odd vibrations and had never been in a serious accident). That was diagnosed as a bad drive shaft. While that was being repaired, a CV boot was apparently torn (just had those boots replaced about a year prior to moving into the area so it didn’t add up). Then, as if that was not enough, the muffler started whistling — high pitch, annoying sound — every time we would reach highway speed (this is all before we even managed to get the car home from the shop last summer). Needless to say, it racked up a ridiculous repair bill. (Previously we had the same mechanic for ~20 years — never had anything like this happen.)

While I wish we had obtained a second opinion sooner (on the prior work), most likely that would have meant taking it to Subaru and as this year’s experience has demonstrated they haven’t been much better. In February, we even called on Subaru of America as this is our 2nd Subaru purchase (customer loyalty?) but they gave us odd explanations about not having any master mechanic in their employ to advise the dealer (the out-of-area dealer that sold us the car told us otherwise by phone). SOA also claimed they couldn’t compel the dealer we are currently stuck with to send over our service records (we requested they review the records, if nothing more, but they claimed the dealer had no obligation to comply with their service records request). All the way around, our experience has been bizarre. (Not even the pandemic situation can completely explain it.) I’d be thrilled if it could be as simple as buying a spray-on type cleaner and unsticking the flap/valve. But if that is all there is to it, one wonders how this solution eluded two different repair shops. :thinking:

I hope your replacement car is not a Subaru because neither of the shops you have been to seem capable of diagnosing one.

It gets worse… When the fire evacuations went into effect, we were down one car and couldn’t fit our pets + bare necessities to evacuate. We made a snap decision to “borrow” a vanpool used for my spouse’s work to fit what we would have been able to fit had we had our second vehicle available. (That made the people who used it frustrated because they had to commute to work in their personal vehicles for a couple days.) Perhaps customers going without their cars for weeks on end is normal in some parts of the country? All I know is that neither the dealer nor the independent shop never even bothered to apologize for 4-6 week stints on their lots. Where we lived before, space was at a premium and nobody had the luxury of keeping a customer’s car on the lot that long — they had to move them out to make room for incoming repairs. This is mind boggling, honestly.

Are you Desert_Outback_Driver on There’s a remarkably similar post there. Elsewhere on that site is a list of codes, P1092 is given as "tumble Generator valve #2 (LH) malfunction (stuck open). It appears that some of the other answers to that post are worth considering.

There are several youtubes devoted to Subaru TGV’s (not the French train). One mentions the possibility of a TGV position sensor mispositioned following service resulting in a stuck butterfly valve. Given the work done on your engine there’s a chance something got damaged or misassembled.

On the forum there’s mention of fixing a similar sounding problem by cleaning and greasing the electrical contacts at the TGV.

The above were located with a few minutes of searching, no doubt there’s more info. out there.

Best wishes

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I don’t necessarily think the lack of power climbing hills is due to an inoperative intake runner. Considering the head gasket issues and potential problems related to that I wonder if the catalytic converters are partially clogged. And I’m hoping that the engine is not worn to the point of major power loss.
Keep in mind that an engine loses roughly 3% of its power for each 1000 feet of altitude above sea level. It adds up.

The best and easiest way to check that is with a vacuum gauge. Many mechanics do not seem to use them or know how to read them.Checking converter clogs is a 5 minute deal with the gauge.
The gauge can also provide a reading about engine wear.

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I agree that with the repair history and the symptoms it’s more consistent with the way it might drive with a clogged CAT. There was a CAT code a few months ago but spouse cleared it and it didn’t come back. (Don’t know if it was stored or not but the dealer hasn’t mentioned any other codes.) Problem is they allow most of their calls to disappear into voicemail so trying to find out if they’ve looked at the CAT or the possibilities Ken2116 mentioned (electrical contacts, TGV position, etc.) is tough due to the phone tag.

Oldtimer_11, sad to say you nailed it. We panicked during our fire evacuation because with only one (compact) car on hand we were unable to fit our pets in our one remaining working car and figured it was time to cut our losses with our 2004. It was still in the shop so we didn’t have it on hand to trade in when we went car shopping. Spouse wanted to buy yet another Subaru (3rd one but our first used purchase). As I type, THAT car is dead in the driveway (engine won’t turn over). The car was purchased with less than 25K — a 2016 2.5i Premium model, single owner and a clean CarFax. I can’t believe our horrific luck!

Our 2004 is still at the dealer (4 weeks and counting), after spending five weeks there prior to the pandemic lockdowns. Our goal was to get it working well enough to pass a smog check and then consider donating it (can’t stomach the idea of junking it with all the money we poured into it last year). Now this. Our only consolation on the 2016 is that we sprung for the full warranty (zero dollar deductible). I learned my lesson: Veto spouse when shopping for cars! :slightly_frowning_face:

I think that if you still like the 2004, then I’d recommend having the intake manifold removed and taken apart. I haven’t done this on a Subaru but this configuration with two different length intake runners was pretty common back then.

The ones I’ve seen come apart where the butterfly valves are located. The valves can get stuck, or the actuator located outside the manifold can go bad. But it is also possible for one of the butterfly’s to come loose from the shaft and fall down further and partly block the whole intake runner, which would lead to the low power situation that you have. Nissan’s were bad about this back then.

I would have both sides done so that you end up with a clean intake, secured butterflies using the new orange locktite or an epoxy on the screw threads and everything working like it is supposed to.

If you can find a mechanic with a borescope, one of those cameras on a thin flexible shaft that can look down inside the manifold, they may be able to determine if the butterflies are OK and free without the disassembly.

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You only get a financial benefit from donating it if you have deductions over the standard deduction and then you are limited to what the charity sells it for and you only get the percentage of what they sell it for that is your tax bracket.

Are you neat Nevada, only two counties in Nevada have emissions testing.

My mother got full auction price for her van donated to public radio. $4300 for a 16 year old van, had a cel so the church would not take it.

OK, but did the $4300 save her ant money on her taxes.? Gid she have enough deductions to put her over the standrd deduction and by how much. The last time I was able to itemize was when I bought 2 cars in yjr same year and the 8 3/4 % salws tax along with my other deductions put me past the standrd deduction at the time. I saved $12, If I would have known that ahead of time, I would not have bothered. And that was before they doubled the standard deduction.

Most charities that accept donated cars, have a flat rate arrangement with a business that includes a junkyard and either a used car dealer or an auction and that flat rate is usually just above junk price. Say junk price is $200. Junk it and you get $200. If the flat rate price is $225 you get a $225deduction. If you cannot itemize, You get $0.00. Even if you can already itemize because you have so very many deductions, you get $225 x your tax rate, say 18%. $225 X .18 = $40.50.

This is an old topic but I thought I’d reply. Turns out that a mobile mechanic who installed an alternator installed it incorrectly and there was some aspect of the linkage that was interfering with the butterfly valves (TGR). What makes this bizarre is that back in February when a Subaru dealer had five weeks with the car, they claimed they replaced an “AY motor assembly” (TGV), and it did not resolve the problem. Two mechanics later after this topic was started and someone pulled out enough of the alternator and the manifold to see what the problem was. I don’t even know how it was physically possible to install it that way as the manifold never came off when the alternator was installed — that said, the car went straight from that repair to the shop that did the head gasket work and I can’t rule out that the car was tampered with there (that was the shop that insisted that we needed an new ECM). It turned out to be a physical obstruction that was tripping the code. No sooner did we figure that out that on the way home it threw another code having to do with the throttle position sensor. The accelerator peddle assembly (with sensor) was replaced and now it’s running fine — except now we learn that the rack-and-pinion is leaking again (after it was replaced in summer 2019 by the same shop that did the head gasket work). Having lost the car for nearly five months out of 2020, we didn’t have it in our own driveway enough to appreciate that the rack-and-pinion repair was faulty.

I have had a lot of old cars in my time because my late father was an autobody repairman (professionally) and backyard mechanic at home — and yet for all the stories I can tell — reason I was such a big fan of the show Car Talk! — I have never in all my years seen a car attempt to “die” in so many ways as this Subaru Outback. (I almost choke when I see the same model Outback depicted on a Subaru car commercial in which they flash a frame of the odometer at 505K+ miles. Ours barely cleared 165K before all hell broke loose despite regular maintenance). Currently our “money pit” is running again with no check engine lights and a recent (successful) smog. For how long before the now-out-of-warranty rack-and-pinion work fails? Who knows. Since I posted my last reply here, the car has only been back in spouse’s possession a month. This is one crazy story to top all crazy car repair sagas, hence I thought it deserved an update.

Happy Holidays, everyone!

Thanks for the update. Who knows, if you got to the root cause, maybe the car will last long enough to be worth the money spent.

It wasn’t the car trying to die so much as incompetent mechanics trying to kill it (and your wallet!)

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When replacing the head gaskets the engine is removed and disassembled, the alternator and intake manifold are removed. Your engine repair mechanic had the opportunity to inspect or damage the intake manifold linkage.

That is not bad luck, that is poor workmanship and it shows that they disassembled the engine twice. Who do you think damaged the intake manifold linkage?

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I watch some motor tear downs on Subie performance on YouTube. It’s in Germany so the language barrier works well with the absurd subie design. I will never own one. Bottom line= works fine till it breaks. Then sell it. Ex failed Audi designers get new jobs at Subaru?