Q7 3.0 tfsi 2015 4L.

Year and a half ago cylinders were fine.
Terrible oil consumption of 1 quart per 1000 miles quickly risen its appetites to 1qt per 500.

Several month ago started to smell gasoline in oil. Garage did this endoscope check saying they found corrosion and scoring. They are proposing ironcast sleeving. Compression in 5th cylinder is barely 8, the others 12.
Aren't scoring usually vertical lines?
For now they say fuel pump should be replaced which allegedly caused oil dilution.

Any thoughts?

 

I am having the exact same issue with the exact same motor and year, Only my compression was higher, 30 lbs in 5, more in the others. 1 score in 5, which I get could let the oil in, but not enough for a misfire and many module faults.
Shop tells me I need a motor swap, almost 10K
Many people tell to do a piston soak and oil flush, which I have done both, and changed the oil.But now my problem is, my system will not reset, meaning, I cannot clear faults in several modules, even with disconnecting both battery cables and connecting them together to drain the system and factory reset the system clearing all modules. How do you like that one.
I told the shop I cannot change the motor until I get the system reset, otherwise, after changing the motor it would still say the same thing, I need a motor because it will still misfire.
I got a post or 2 going pertaining to this subject.

 

Hi,
I see you've been posting about your car's extreme oil usage in past months, which generally means you've got big problems with the PCV failed internally and/or the low-tension piston rings are now carbon-captured and are basically ineffective at keeping oil in the crankcase and compression in the cylinders. Oil dilution to the point where your oil smells of raw gasoline should have been a clue that your rings weren't sealing and/or you had some other severe issues going on with the motor. Scoring is from the piston rings not being able to move and seal the cylinder properly in conjunction with the extreme oil dilution you mentioned, which has the net effect of thinning out the motor oil and eventually it gets to the point where it loses the ability to protect your engine...gasoline is a very effective solvent.

FWIW, there's another owner currently actively posting on his 3.0 TSFI motor is basically doing the same thing as yours is, and his shop is suggesting an engine swap. Of course his Q7 engine does have a fair good bit of mileage on it already, and so swapping out or fully rebuilding his existing engine kind of makes sense.

Not sure how the HPFP (primary fuel pump) could possibly figure into the oil dilution on your car, as oil dilution occurs simply from normal process of fuel sprayed into the cylinders, in addition to any combustion gases that make it past the piston rings. It is normal to have some oil dilution even if everything is working fine. Where it really becomes a problem is when you use extended oil change intervals, like those Audi recommends for these Q7s. It's too long and contributes to the eventual problems with the rings capture/oil dilution/oil consumption from the rings issue, etc., etc.

The HPFP itself is simply a pressurizing pump for the fuel system to allow for more precise control of fuel metering. You definitely don't want that pump to fail on you, as it can often have catastrophic fuel system contamination as an end result, but that said, it's not fair to blame it for the oil dilution issue, which has everything to do with your severely carbon-captured piston rings...that's why your compression is sooooo LOW, and it's likely the exhaust/intake valves are not sealing well either due to carbon build-up in the cylinders, which impacts/reduces individual cylinder compression even further.

 

Here's a link to help you understand oil dilution: https://cartreatments.com/oil-smells-like-gas/

Bearing in mind, this doesn't even consider the fact that your PCV was definitely a problem for your car prior based on your posts, and if you don't fix the PCV in a timely manner, then the extreme crankcase vacuum pressure from the failed PCV can cause permanent oil seal / engine damage as well...kinda like the perfect storm of convergence on this motor.

 

Thanks for the reply. I could easily take off oil cap while engine is running. Supposedly you should have huge suction with failed pcv, but who knows.
I have no idea what to do next. Shop said no need to change pcv since engine is in bad state. Only rebuild will help where the insert sleeves into bores.
Should I still try decarbonization with B12 berryman maybe?
I previously poured liqui molly 200km prior to oil change that supposed to clean the rings. I also poured in gas PEA cleaner for injectors a couple of times. Seems like piston tips are still very black. Maybe those chems don't work.

 

Sorry, 5th cylinder is 10 ATM not 8. I get contradictive responses in garages. Some say it could be injectors, others saying it's rare it is fuel pump due. While there is an opinion that direct injections can cause this. On photos I didn't see vertical scratches that I'd expect from scoring.
Why in the world it is so hard to find professional mechanic.

 

They said crater in the cylinder most likely was caused by fueled oil igniting inside a cylinder.
Fuel gets into a crankcase via some leaking fuel pump passages. I did have an intermittent error few times "insufficient sealing in fuel system". Computer considered it a low priority.

 

This sounds exactly like what is happening on my engine as we speak, same year 3.0T too. Started getting a misfire over the past month or 2, showing on cylinder 6. Also noticed since going into winter my mileage has slowly been getting worse, could be winterblend fuel but seems like more then that. Had my guy pull the plug and coilpack, plug looked like it could need to be done. Scoped that cylinder while we had it out and there's definitely signs on oil burning and some very slight scoring on the backside of the cylinder wall. Replaced that spark plug with a new OEM one and I'm still getting misfires, had cylinder 5 come up as misfiring now but that has since gone away. Still have a permanent code for cylinder 6. I also told him about the starting issues I've been having for months where on cold start, the engine will take a few seconds to actually turn over. For some reason, this is way worse when I use the button and not the key to start it. There have been times where it takes close to 10 or 15 seconds to finally fire when using the button on cold start. Sometimes it won't stay running and I have to hit it again too. He hooked up his laptop with Vagcom and monitored the fuel pressure bleed off as the engine sat over time, it went from 37 or 27 psi all the way down to under 5 psi in 20 to 30 mins. He said most likely my HPFP is bad and after looking into this more, it definitely seems that way. I pulled my oil cap off the other day after driving home from work and it definitely smells of gas pretty good. I plan on getting a new HPFP and also doing all my plugs, but my engine is still burning a ton of oil when it shouldn't be that bad. I had the entire PCV system and associated hoses completely replaced not even a year ago right after I bought my car for peace of mind, also the water pump, thermostat, and all new gaskets and seals on everything that had to be removed. No reason it should be burning through this much oil in my opinion. I'm at a loss though and hoping after I do both of these that something improves. I'm at 119k on mine, forgot to mention that.

 

Damn these engines. In mine I had never any misfire codes. Couple of insufficient fuel sealing, and several pcv errors. I went ahead with ordering new fuel pump via the garage and will change oil. Unfortunately I have to drive this weekend about 60km. Engine sounds good and drives just fine. Always have 2 liters of oils with me (laugh through tears). Should never have bought this trash.

10k USD for a used motor or just for labour? Is it USA?

I've read misfires can also pertain to coils, not spark plugs themselves.
90% of forum people say oil burn due to piston rings. Unfortunately no ship would want to do the decarbonization.

 

Seems high but for the engine itself, plus labor for removing and reinstalling everything, that doesn't sound too far off. I am in the US, yes. Piston rings sticking is most likely the cause, I may need to get the heads walnut-blasted (cleans carbon off the valves and intake ports) and see if that helps. Could be a coil pack but I'm told these usually don't fail and are pretty reliable, that's the next step though if changing plugs doesn't solve it. THEN, if I'm extremely unlucky, could be an intercooler core leaking coolant down into that cylinder possibly or also timing chain related. At that point I'm better off just selling it because I can't afford a timing job on this, intercooler I could fix but that'll also cost a pretty penny.