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Our 2017 Q7 with the 3.0 V6 has about 100,000 miles on it now and has burned oil since we got it a year ago at 8XXXX miles. When we first got it., it burned a quart every 1500 miles. For the last couple months it's gotten worse, about a quart every 300 miles. I've been worried about the long term consequences of this level of oil consumption on the catalytic converter.

Despite the oil consumption, the car runs well and we were going on a 300 mile roundtrip today and were about 50 miles away when it started running poorly. It felt like it was missing. We pulled into an autoparts store and their code reader said it had a P0302, misfire on #2. We changed the coil and spark plug on #2, but the CEL stayed on and it still ran rough, so we headed back home. I noticed on the way home that the missing seemed to go away if I floored it, or if it were coasting. It was under partial throttle that I had the miss.

When I got back home I tried my code reader and it said that it had a P0300 (general misfire), P0301, P0302, and P0306 (misfires on #1, #2, and #6. It's possible that I had all these codes when I was using the borrowed code scanner and I just didn't know how to see the other codes.

I'm worried that the catalytic converter could be clogged and causing this. I was going to try doing a compression test and changing the rest of the spark plugs. The spark plug that was in it had a lot of deposits.

pluga

plugb

I don't know if it was original

I was going to try replacing all the plugs and doing a compression check. I'm not sure what could cause a sudden onset of misfires on multiple cylinders on this car, especially one that seems much worse at partial throttle, but mostly goes away at full throttle and at no load.

Thanks

Eric
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3 Answers3

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your symptoms indicate car needs internal mechanical work. See what your compression test tells you about engine.could be worn piston rings, valve seals, etc.

Bill Sullivan
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Plugged cats is a definite concern when you're burning that amount of oil. I wrote a separate answer on how you can check your cats.

Considering your engine is the supercharged 3.0L V6, I'm wondering if the supercharger has bad seals and is allowing oil to be pushed past it, and then passed into the combustion chamber. That is a lot of deposits on the spark plug. 100k is usually the point where most manufacturers recommend new plugs, so you're doing it at the right time. A fresh set of plugs should help with how it is running, regardless of how much oil is being burned.

Pᴀᴜʟsᴛᴇʀ2
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I have an Audi Q7 (2008)

I've found that when mine would leak oil (it would pool up on top of the valve cover and in the sparkplug wells), it would run like crap and misfire EXACTLY like you described.

I'm pretty sure I had the same issue, and assumed it was clogged cat. Haven't yet fixed it though but from my experience:

Before you mess with the cats, remove the O2 sensors and use a borescope to look at the cat material. If it looks like a honeycomb its fine, assume if you can't tell that its fine. A clogged cat would make your vehicle stall out constantly. I tested this by blocking my uxhause flow before the cat when i had the cats taken off. This engine is very very sensitive to intake and exhaust flow.

You should do an oil change and use thinner or thicker oil. I had some improvements with different viscosity oils.

Sorry I couldn't be more help. I'll be watching this Q hoping for a solution for mine as well.

HNx
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