2015 S3 down on fuel and power

[Damo S]

The last week or so I notice my car is down on fuel, probably by over 10% given like for like driving (getting low 30s at speeds that were previously giving high 30s or 40). I've also noticed that it feels a bit down on power as well, not all the time and driving it hard for a period does seem to shift the power problem somewhat. The car feels like it was in the heat of the summer when the ECU was backing the power off. It also seems to be a tiny bit little lumpy on tickover.

I'll try to get a diagnostic done later today and it could be just a fault code but fact it's not consistent makes me think its possibly something else.

On the old 3.2 these were the kind of symptoms that occurred when the coil packs were on their way out (but not failed completely). I'm wondering if it's the same thing could be happening here, although 25k miles seems a bit premature for them to start giving up.

 

[Damo S]

Used a work colleagues OBD reader and App. No fault codes stored.

 

[winrya]

Can’t comment on the power deficit but since the weather has cooled off the past few weeks my consumption has increased a good 10% (which is normal due to longer warm up times, extra drain from heated seats, lights, heaters, screen demisters etc)

 

[S32B]

Have you changed where you normally buy fuel from or let it run low on fuel? Could be some muck in the fuel system that need to pass, try a tank of V-power in it.

When I had the S3 I filled up @ Sainsburys on the way to Scotland, the car felt like I'd put the wrong fuel in it, got to Glasgow and I filled up with V-power, 3 mile down the road everything was back to normal

 

[Damo S]

Weather cooling: Yes I did consider this but it also happened on an 80 mile trip at the weekend. I wondered if it was the headwind on the way down but had the exactly same on the way back with a tail wind too. Even the instantaneous figure (once the engine was properly warm) seems well down. It was reading 34 to 35 (on flat bits) at 70 mph when I've previously averaged 38mpgs on a trip doing 80mph. It's definitely not right and by some margin.

Changed fuel: No, not before it started playing up but you are right that it had run very low. I was slightly miffed about this actually. It went in for the MOT and tracking to be sorted last week with about 50 miles left and came back with just 5 left! I don't know whether it had been sat around idling for ages or whether the guys who had done the tracking took it for a proper spanking up the road. The latter is unlikely as Ive used this garage for years but I have no idea. I would say its been worse since then, but it was not entirely right before this. I think I'll do what you suggest: A tank of V Power and see what happens.

 

[AlS3BE]

Have you checked your tyre pressures.
High pressures will give you better economy and low the opposite.
Maybe your pressures were adjusted for the tracking.

 

[S32B]

Changed fuel: No, not before it started playing up but you are right that it had run very low. I was slightly miffed about this actually. It went in for the MOT and tracking to be sorted last week with about 50 miles left and came back with just 5 left! I don't know whether it had been sat around idling for ages or whether the guys who had done the tracking took it for a proper spanking up the road. The latter is unlikely as Ive used this garage for years but I have no idea. I would say its been worse since then, but it was not entirely right before this. I think I'll do what you suggest: A tank of V Power and see what happens.

I'd put my money on it sucking all the crud up from the bottom of the tank...give it a good red line in each gear (somewhere safe obviously).

 

[ckl999]

Anybody know somewhere for a decent remap in Harrogate?

 

[Damo S]

Full tank of V power now so lets see what happens. The clutch is pretty much toast so thrashing it might not be on the cards. Its going in tuesday for a performance jobby to be fitted (along with an uprated intercooler which ... just kind of magically appeared on the same order )

 

[ictus_duplo2]

My fuel consumption has dropped noticeably with the cold weather over the last couple of weeks. The fuel tank range really drops which I assume is down to the poor initial MPG. Its gone from 38-40 on my run to work to 33mpg-ish. Start/ stop does not kick in , heated seat on and slow to get to temp.

 

[TYb]

My fuel consumption has dropped noticeably with the cold weather over the last couple of weeks. The fuel tank range really drops which I assume is down to the poor initial MPG. Its gone from 38-40 on my run to work to 33mpg-ish. Start/ stop does not kick in , heated seat on and slow to get to temp.

Same, I did check tyre pressures though and they had dropped significantly with the colder weather.

 

[Damo S]

OK, but that doesnt explain the car feeling a bit down on power. It should be up on power given the cooler charge temps. To me it feels like it comes on boost and then decides to back things off, but not all the time.

 

[Damo S]

It is definitely coming on boost for a second or so and then backing the timing off. It was really noticable this morning when planting it in 6th at 2krpm. Turbo kicks in fully and then a second or so later a sudden reduction in power.

 

[AlS3BE]

Could it be over boosting? Maybe turbo actuator sticking a little and ecu is pulling it back and then over doing it. Not sure how the s3 dials it back when it detects Too much boost.
These new turbos comes on boost really early so if it’s over boosting then I would assume the ecu will be quick to react.
Could also be coolant temp sensors, maf, and other sensors. Coolant temp sensor will be the main suspect that has an effect on your economy especially if it thinks your car isn’t warmed up properly and if it thinks it isn’t warmed up then ecu not let you drive hard or rev it hard.

 

[Damo S]

I don't think its overboosting as if it was then the initial torque would feel stronger than before, which it doesnt. I would agree its likely to be a sensor starting to fail, perhaps the MAP making it underfuel -> detonation, or possibly a knock sensor which claims that its detonating when it isnt. I've mentioned it to the garage doing the clutch so hopefully they will be able to work it out. I've heard that MAP sensors are cheap so it might be worth just fitting a new one anyway. It was a failing MAP sensor that lead to the destruction of the engine in one of my old performance cars just after I'd rebuilt the ****** thing.

 

[AlS3BE]

Get a cheap obd reader to get live data and drive around and see what the sensors are showing. That’s should give you a better idea.
I’ve seen coolant sensor show really low readings in the obd reader even though the dash says it’s around 80-90 degrees so I wouldn’t believe too much what you see on your dashboard.

 

[desertstorm]

Usually MAP sensors just fail completely. They don't start reading inaccurately. The MAF sensor is more likely to be the culprit. If you have a K + N or other oiled type air filter and it's over oiled this can get on the MAF and affect it's calibration. Or they just deteriorate.
Try disconnecting the MAF and see if the driveability improves. Could also be a boost leak, check all the hoses and connections for splits or leaks.

 

[Damo S]

Yes, I got through several MAF sensors on the old 3.2 quattro. The car is stock currently so no oily filter or anything

 

[Damo S]

Just for some closure to the thread, and in case anyone else has a similar problem. It took me some time to come up with concrete proof that there was an actual problem which basically involved getting my own OBD reader and scanning the test result logs. Turns out that the ECU was recording misfires on cylinder number 1, at which point I booked it in with Audi to be fixed.

The problem ended up being that somehow a bolt (which looks a lot like the ones holding the plastic casing around the cam shaft pulleys to the head) had found its way into the cylinder head and damaged the number 1's lobe on the exhaust camshaft. The only way in, if not present from manufacture, is through the oil filler cap. Unfortunately, because I'd had the clutch changed and bigger intercooler fitted not long before it went into Audi they pointed the finger at the "3rd party garage" and took no responsibility. In a nut shell, irrespective of me moaning about and having evidence of trying to diagnose a running issue several weeks before that work was completed they still told me to get lost. The bill for replacing the exhaust cam, oh, and a new injector they tried came to 3 grand. To give them their due they had spent 33.8 hours on the car from start to finish but only billed me for 17 hours at a reduced rate. In affect their way of going "50/50" on the issue.

I got my car back from Audi yesterday having been there for the best part of 2 months. Seemed a bit sluggish at first but it felt better after some time ... and then this morning, engine management light: po420 some garbage about the cat but could be many things causing emissions problems. So next week its going back in to have that sorted out. ***.

An expensive lesson in why not to muck about with your car in any way at all if you want to use the approved warranty, including using a cheaper garage to fix a failed component not covered by the warranty (clutch), because if they can get out of paying up for an expensive repair then they will.

I'm still looking into whether its worth taking them to court under consumer law: the car not being fit for purpose at point of sale. As it was reported within 6 months of purchase the onus is on Audi to prove it didnt exist when I bought the car, and Im not sure they can. Their diagnostic check pre-sale shows no misfires, but that doesnt prove the bolt wasnt already present inside the engine or hadnt already done some damage to the shaft, which would worsen over time with use. Unfortunately for me, the earliest recorded misfire in the ecu's "unwipeable logs" (according to Audi) was some 10 days after the clutch change work which conveniently makes it look like it was caused by the garage (even though they didnt go near the filler cap). However, I know 100% that some issue existed well before then and the same symptoms have persisted throughout the ordeal. perhaps the damage just wasnt bad enough to register a misfire until later but this really has not helped me at all. Despite the onus being on Audi, I think if it went to court I would have to somehow show that the lack of recorded misfire at point of sale isnt enough to prove 100% that the physical problem didnt already exist to some extent. I will be seeking legal advice on this.

 

[AlS3BE]

Sorry to hear about this. Have you tried the ombudsman? Think it’s £200 for them to do a review but it might be too late for that now it’s fixed. They are a helpful bunch at least.

 

[Damo S]

Update. The cat is shot but at least they are replacing it under warranty. Interesting, to me it seems incredibly unlikely that just 2 weeks of misfires (as audi claim) would wreck the cat. I would say its more indicative of the longer term problem.

 

[Khufu]

an expensive tale . I dont think it takes too long for unburnt fuel to ruin a cat. We did one on an Astra after doing a coilpack as it had caused the cat to totally melt. Owner said it hadnt been missing for long but we suspect it was only because engine wouldnt rev over 3k that she brought it in.

 

[CoffeeAndJam]

Update. The cat is shot but at least they are replacing it under warranty. Interesting, to me it seems incredibly unlikely that just 2 weeks of misfires (as audi claim) would wreck the cat. I would say its more indicative of the longer term problem.

Sorry to hear that. Did your engine misfires ever trigger a CEL? How many misfires were you getting and how long was it going on for? It does seem strange it would ruin the cat so quickly.

My engine still misfires pretty regularly on certain cold-starts but never throws a CEL. Hope it doesn’t ruin my catalytic converter.

 

[Damo S]

Never any codes. the only reason I discovered it is because I went digging in the logs. I was seeing between 120 to 200 after a 30 min drive. The earliest recording of a misfire, according to the ecu, was on the 25th november so about 3 weeks before it went to audi. However, it was intermittantly running badly under certain conditions for at least 6 weeks before that, and most likely longer (probably since I bought the car in july but just not as extreme). Whilst the poor running got a bit worse over time the actual symptoms didn't change over the whole period even from when it started recording the misfires. The same intermittant behaviour has been pretty much a constant, although it would be less noticeable or even go away completely on a hot day (which is why I think I barely noticed it over the summer or during the test drive) or if I gave the car a bit of stick after it played up. Consequently, I have no idea how long its been running poorly. I suspect the "misfire" instances most likely started because the damage on the cam shaft degraded further to a state where it became detectable by the ecu.

what is slightly odd is that on a 30 min journey at an average for say 2k rpm thats 60,000 rotations out of which it thinks only 200 were not right. That's a pretty low hit rate considering the physical damage to the shaft which would be present and affect every rotation (one would have thought).

 

[Damo S]

Car is back on the drive again. The cat was replaced but the warranty company refused the pay out due to it being caused by the previous issue, apparently. However, the dealership said they have taken the hit and just replaced it without charging me. If true then that's some nice good will from them (secretly they know the truth IMO).
Hopefully it will stay working long enough for me to test the car properly to see if they have actually fixed the original intermittent problem. It does feel fairly strong in terms of power and the fuel usage looks better so lets see.

 

[pop80_uk]

Full tank of V power now so lets see what happens. The clutch is pretty much toast so thrashing it might not be on the cards. Its going in tuesday for a performance jobby to be fitted (along with an uprated intercooler which ... just kind of magically appeared on the same order )

Bit off topic, but where are you taking it for the clutch? and do you mind me asking how much?
Thanks

 

[Damo S]

Quattro tech in St Ives. 1300 quid for sachs organic and a new audi DMF. However, whilst car was with audi I asked them to have a look to see why sometimes I had trouble getting it into 5th gear. They just said "clutch seems heavy so its possibly to do with whatever was put in there". Yes, a clutch that will hopefully last more than 25k miles you utter morons! Ive not had the 5th gear issue since the new clutch was installed so perhaps it was just a symptom of the failing original clutch or perhaps linkage adjustments were made during the install.
One consideration is whether having an uprated clutch would cause a warranty claim problem if there was an issue with gearbox or drive train. Their response suggest they didnt even bother looking further once they suspected it wasnt an Audi clutch. They dont need much of an excuse to not pay out, it seems.

 

[AlS3BE]

Struggling to get into gears in my experience is normally linkages or synchros.
Sometimes changing the gearbox oil helps as well.

 

[pop80_uk]

Quattro tech in St Ives. 1300 quid for sachs organic and a new audi DMF. However, whilst car was with audi I asked them to have a look to see why sometimes I had trouble getting it into 5th gear. They just said "clutch seems heavy so its possibly to do with whatever was put in there". Yes, a clutch that will hopefully last more than 25k miles you utter morons! Ive not had the 5th gear issue since the new clutch was installed so perhaps it was just a symptom of the failing original clutch or perhaps linkage adjustments were made during the install.
One consideration is whether having an uprated clutch would cause a warranty claim problem if there was an issue with gearbox or drive train. Their response suggest they didnt even bother looking further once they suspected it wasnt an Audi clutch. They dont need much of an excuse to not pay out, it seems.

That is a fantastic price! All the quotes I have had are £200 - £300 more than yours for the same package.
Also some want to change the DMF no questions, its a must. And others are telling me the standard DMF will be fine to reuse and not to worry.

Sounds like Audi dealer is washing their hands.

 

[Damo S]

I gave the car a good run this morning and all the fixes does seem to have resolved my original running problem. It does feel pretty rapid too. However, it recorded 7 misfires on cylinder number 3 this time, and 0 on all the others. I guess I'll have to monitor this and if it continues it might have to go back, again.

Turbo boost pressure still seems a little unstable. I did see 17psi at one point, which as I understand is what its meant to run, but generally it was only going up to around 15 most of the time. A youtube video of a golf R being put through its paces using an APR boost gauge showed theirs peaking at about 15psi too, pretty much inline with what I'm seeing on mine.

Interesting:
"I have an analog gauge on my stock MK7 sport GTI. In hot weather I can peak around 19psi, sometimes 20psi. Colder weather around 16-17psi"

I remember reading somewhere that the ECU does try to ensure the power output is consistent so maybe this is an example of that in work. Perhaps mine is a little lower at times because of the uprated intercooler which will be effectively mkaing it appear to the car that the ambient air temp is a bit colder.

Some googling also found a graph where someone recorded the boost pressure in 3rd gear and the boost pressure seems to vary by a few psi up the rev. This behaviour is a little baffling and I assume it is something to do with the electronic wastegate control and the ecu perhaps trying to moderate the power / torque.
It seems as if the ECU tries to moderate the boost pressure when it comes on boost too. The boost doesnt fly up to 15 psi it gets up to about 12 psi fairly quickly but then further progress slows up a lot which I assume is the ecu trying to prevent overboosting (overboost - a nice feature of the old school turbo wastegates providing a nice shunt of torque when it came on boost quickly but a silent destroyer of engines). Whilst safer for the engine it doesnt excite the butt dyno quite as much. These ****** cars are just too complicated.

 

[CoffeeAndJam]

Happy to hear the fix helped. And by the fix, do you mean your cat or the problem with the camshaft? Just curious.


7 misfires is nothing compared to what my engine logs. My engine still logs misfires on all cylinders once warmed up. Anywhere between 3-20 per cylinder. No pattern what-so-ever, just random between all cylinders.

 

[Damo S]

The cam shaft replacement I would say (but they also replaced the injector but I dont believe that was at fault in the first place). The replacement cat has sorted the ECL meaning its not running limp again and seems to be running how it should.

Only 1 misfire this morning on cylinders 2 and 3.

 

[CoffeeAndJam]

Only 1 misfire this morning on cylinders 2 and 3.

Great! Is that after a whole drive or after a cold start only?

 

[Damo S]

After a 30 minute commute giving it some stick at times

 

[CoffeeAndJam]

That’s great to get so few on a 30 minute commute. Sounds like it was fixed like you said. Thanks for keeping us updated with the progress and fix.

My average is up to 7-15 on all cylinders for the same commute time. Still makes me wonder if it’s “normal” like everyone is telling me. Definitely not very comforting after shelling out over $10k for an engine & turbo.

 

[Damo S]

Indeed, "normal" isnt exactly comforting when you've had misfires wreck your engine previously. I had this on an old car. Neither fun or cheap and leaves you feeling paranoid.