To keep it short, on the road home from visiting family for the holidays, our 2017 Audi Q7 3.0T started driving very rough and drive system malfunction alert occurred. No smells, smoke, or alarming sounds coming from the car, just running really rough/wobbly feeling and got that way even while idling on the side of the road. Pulled over immediately (car load of kids, xmas presents, luggage and all) and my OBD11 scan showed cylinder misfires and a hide cylinder static fault codes (it also tripped an intermittent PCV regulator valve code as well fwiw). Since we were 400 miles from home, we sent it to a nearby mechanic who looks at Audis, and he said that spark plugs definitely needed to be replaced (we were at 128k miles and spark plugs were new as of ~60k miles - we now realize we pushed this way too long, so I'll take the blame on that one, even though I feel like our mechanic could have informed us of spark plug intervals on our car as least once in the past year or 2). They also ran a dry compression and leak down test and said that cylinder #5 needs its exhaust valve fixed/replaced (it was the only cylinder that failed the test). No comment on coils or any other leaky gaskets so I assume those were ok.


Unfortunately, he then went on to say that he basically doesn't have the manpower to tackle this, suggesting "it's a gamble" to fix and you'd have to practically rebuild the engine to make sure everything is 100% fine (I can only assume he means tearing down the engine to inspect the piston rings at that point). While it is technically accurate to basically say "a new engine will fix it," it seems excessive based on the info that has been established. I'm not suggesting he was being dishonest at all, it just seemed a little hasty... almost like a doctor jumping straight to saying a patient with one bad valve needs a full blown heart transplant vs addressing the bad valve that seems to have been pretty clearly identified.


Bottom line is we are having the car shipped back to our hometown mechanic to get his opinion, and meanwhile I'm trying to square what option is the most cost effective on a 7yr old car between:

1. replace/fix a bad/burnt exhaust valve on the one bad cylinder (and obviously replace all spark plugs)
2. tear down the engine all the way to the piston to inspect for issues there (in addition to replacing/fixing the exhaust valve and new spark plugs)
3. replace the entire engine (a used one for sure)

I'm just finding it hard to believe that the engine went from fine to 100% toast but my knowledge base with cars is more on the interior/electrical side vs under the hood. We are fortunate to have family able to lend us a car but I'm just trying to figure out ballpark costs for each of those options would look like - and what anyone else who maybe has experienced this would ultimately recommend?

Fun sidenote - I did manage to get in touch with our local Audi dealer and just over the phone the tech said "Yea I mean you just assume replace the engine entirely... that's about 30k." On a 7yr old car prob worth ~15k, I almost just laughed and hung up.

Anyways, any help appreciated in here... Starting the new year with a bang!

 

Was the vehicle consuming oil and asking you to top it up, and if so how many miles between it asking you to add a quart?

 

128k miles... and unfortunately yes, it was asking for a quart relatively often (the typical "please add a quart, you can keep driving" notification)... less than 1,000 miles. Car still always ran fine though... not rough at all.

Was consistently given the usual "these supercharged V6s just chew oil at higher mileages" explanation at local shops and Audi itself (go figure). Troubleshooting here in the past I had read about possible piston ring damage, but was under the impression that 1) it was pretty rare and would be more noticeable in the way the car drives and 2) obviously a much more expensive adventure for someone to investigate. The car is 7yrs old and been paid off for a while so I wasn't eager to have my family down a car on top of who knows what kind of money for essentially exploratory surgery on it. Considering the OBD11 scans never produced any alarming static fault codes on the engine, like cylinder misfires or pressure too high/low or anything (until now), I figured the car was still in decent shape considering the mileage and all.

Obviously in hindsight the possibility for internal engine/piston damage/issues has turned out to be not as rare, although I'm not necessarily sold that is/was the issue anyway. I'm possibly out of my depth, but I think the spark plug at least on cylinder 5 was run down and it essentially melted the exhaust valve... also think the engine is in need of a piston soak which seems to be par for the course for any of these FSI engines particularly at higher mileages. Fwiw, we always got plenty highway, high speed mileage on the car so I kind of hoped/assumed a lot of that buildup would get burned/blown out of the car since it was getting consistent highway mileage, but I fully admit that could be a gross misunderstanding on my part.

I know I'm trying to glass half full this thing, but my hope is the car could be essentially back on track with a new exchange valve on the bad cylinder (per the compression and leak down test done by that one mechanic), new spark plugs, and then honestly a piston soak to maybe clean out any and all carbon deposits. But as mentioned before, I'm weighing the cost-benefit of that vs just replacing the engine outright (or seeing what I could get out of the car as-is and just move on).

I'll also add that if I was having my mechanic do the following work, I'd also see about replacing the PCV regulator because that intermittent fault code went off as well and I know that also can cause issues too, albeit not as immediately detrimental to my knowledge.

 

That really sucks. These failures seem to be more common as these vehicle age, and the fact that the mechanics are saying that high oil consumption is normal on these engines is doing no one any favors. Be prepared for some skepticism, as there are some deniers on these and other forums which suggest that these failure reports are fake.

 

I don't understand this idea that they are fake, there are literally multiple reports of this exact thing on small Canadian automotive forums that are not even Audi-specific, in a single Audi thread. This is clearly a significant issue with these vehicles.

Sounds like with the vehicle worth $15k I would move on.

 

Supposedly the PCV system capacity was reduced for Euro-6 emissions standards, leading to faster carbon buildup. With only a few years left for installation of the engine in new cars, I imagine Audi wanted to spend as little as possible in order to certify it.

You still need to scope the valves on a used engine, but removing the heads for cleaning and replacing the PCV valve is probably a better course of action.

Audi could have done a better job, but there are also external influences that do not promote reliability of their product. If you install a new or rebuilt engine, do 5k oil change intervals.

 

Appreciate the insight @kelisko and yea while I check this forum every so often, I seem to have completely missed the carbon cleanout discussion... a costly bummer indeed (the last time I was on here I posted pics and an update on replacing the overhead cam system module... Jan 2024).

I know your ultimate advice is just replace the engine and/or junk the car (mainly due to risk that the block or pistons or something else are toast), but if you were to play this out based on the info I've got, the steps seem to be:

1. Replace damaged cylinder valves - it appears exhaust valve on #5 is for sure burnt/ruined (mechanic did not specify that all were burnt or just one but cylinder 5 is the only one that failed the compression test); regardless, check/replace other ones as well
2. Piston soak to clear out any carbon in all cylinders (B12 method... shoutout to eurotrash)
3. (for good measure) - replace the PCV regulator
4. (also for good measure) - replace the spark plugs

It is my understanding that all of this can be done without having to drop the engine, correct? I'm not saying that means it's easy work, but certainly much more manageable and less time consuming (and therefore less expensive). The mechanic who said my exhaust valves were burnt up clearly had to take off the head to see that unless I'm misunderstanding something. So if it was that easy to do that (he was able to tell me about it in less than a day and only charged me for a diagnostic), wouldn't it presumably be manageable to replace exhaust (or even intake valves) that are right there in plain view if they are chipped/burnt/whatever?

The car fixed up would be worth prob $12-15k, so I'm saying if I can get back on track for, let's say, solidly under $10k, that would be somewhat of a win in my book. Hence me entertaining all options. Now if doing the work described above vs getting a used engine with, say, 40k miles on it, comes to about the same price (let's say between $7-10k), then of course, you just assume replace the whole engine and then stay on top of maintenance (piston soaks, prompt spark plug changes, etc). But if it's literally half the cost to do the work above, I'd opt for that.

 

He most likely checked the valves with a borescope via the spark plug holes...

 

There is a vocal group (I'm not one of them) that suggest that since a relatively new user posts their story of their engine detonating after experiencing oil consumption issues, gets attacked for "whining", subsequently does not follow up, then it must be fake. I don't know if they think it is Russian disinformation or aliens, but this group exists. Perhaps they feel it is a smear campaign against their beloved car brand.

I do believe that this engine, despite being good, does have flaws. Fortunately, if you are aware of them, they can be mitigated. Unfortunately, if you follow Audi's advice, then you run the risk of it grenading. Bottom line, these Audi's are not bulletproof, and do require special care, which is not for the faint of heart.

Audi's manuals and dealers compound the problem by dismissing and normalizing the oil consumption issue, despite it being continually brought to their attention. This same vocal group does not seem to see a problem with this issue, instead blaming the owners that they should have known better.

 

Ahhh ok... that's my naivete on full display there... apologies.

Even so, would a "valve job" aka take the engine head off and inspect, replace bad/burnt valves, and then in no particular order do a piston soak and/or compression test, leak down afterwards to test out everything be a far less costly job vs a full on engine replacement?