Exhaust Smell Under Hard Acceleration (V12, AE31 engine)
Discussion
Hi, a question for DB11/DBSS owners with a V12 engine - does your car produce an exhaust smell under hard acceleration? It is also reproducible in a closed garage and revving out the engine. The exhaust smell reminds sulfur. The vehicle does not smoke, throw any codes, and does not seem to be consuming engine oil (but I cannot rule this out). The dealer checked it, says "nothing abnormal". But personally, I'm having a problem believing it. Could it be a sign of a failing catalytic converter (35 000 km on the clock)?
Edited by ress on Thursday 9th February 07:48
Hi Ress, I had exactly the same thing happen to me with my Vantage. however, it happened straight after having hi-flow cats fitted. The car didn't throw any codes, drove perfectly etc. but under hard acceleration the smell was there. All I can say is now the smell does not occur, it's almost like the cats needing bedding in. Told the garage (AHM) that fitted them as I had other things done at the same time such as new twin plate clutch etc. and they said it happens every time they fit them but it should sort itself out.
Can you clarify a little better? - maybe describe the smell? Is is kind of sweet? That could be uncatalysed unburned hydrocarbons.
How do you know it smells under acceleration? You as a driver or passenger are surely way ahead of anything fired out the exhausts?
You mention ‘reproducible’ an a garage by revving out the car - be a tad careful (no engine really appreciates being revved up under no load and especially when cold). It would take a fair while to reach full working temp in a garage.
I have a twin turbo V12 5.2. I have never smelled anything unusual, but my V8VS with no primary cats and 200cell secondaries produces very strange smells until the racing cats get hot enough to start working properly.
How do you know it smells under acceleration? You as a driver or passenger are surely way ahead of anything fired out the exhausts?
You mention ‘reproducible’ an a garage by revving out the car - be a tad careful (no engine really appreciates being revved up under no load and especially when cold). It would take a fair while to reach full working temp in a garage.
I have a twin turbo V12 5.2. I have never smelled anything unusual, but my V8VS with no primary cats and 200cell secondaries produces very strange smells until the racing cats get hot enough to start working properly.
Edited by Calinours on Friday 10th February 17:06
Can you clarify a little better? - maybe describe the smell? Is is kind of sweet? That could be uncatalysed unburned hydrocarbons.
I'm not an expert but it reminds me of a smell of a car without a cat.
How do you know it smells under acceleration? You as a driver or passenger are surely way ahead of anything fired out the exhausts?
In a tunnel, windows fully rolled down.
You mention ‘reproducible’ an a garage by revving out the car - be a tad careful (no engine really appreciates being revved up under no load and especially when cold). It would take a fair while to reach full working temp in a garage.
Agree. I usually do not rev the car in the garage and never when it is cold. A friend asked to rev it out to hear it - and that's how I got the smell for the first time (the car was fully warmed up after a drive).
I'm not an expert but it reminds me of a smell of a car without a cat.
How do you know it smells under acceleration? You as a driver or passenger are surely way ahead of anything fired out the exhausts?
In a tunnel, windows fully rolled down.
You mention ‘reproducible’ an a garage by revving out the car - be a tad careful (no engine really appreciates being revved up under no load and especially when cold). It would take a fair while to reach full working temp in a garage.
Agree. I usually do not rev the car in the garage and never when it is cold. A friend asked to rev it out to hear it - and that's how I got the smell for the first time (the car was fully warmed up after a drive).
Have you or a previous owner modified the exhaust system at all? Is ‘check engine’ light coming on?
Standard, The EU6 AE31 shouldn’t be smelling at all at any time. I can start mine and have a sniff when it’s just started from cold or super hot and not detect anything, and I’ve still a keen sense of smell, even though the eyes and lugs ain’t what they were.
If you don’t have a decent OBD reader, for peace of mind I’d advise taking it to an AMLMD for ignition and fuelling diagnostics and gas analysis. I’d be hopeful it’s something trivial, like a dodgy batch of fuel or maybe old fuel? - but if not, and the exhaust hasn’t been modified, it could be anything from blocked filters to failing coil packs to oxygen sensor and damaged catalysts.
Of mine, I feel I could almost breathe the gas coming out the back of the DB11, yours should be that clean. My modified V8VS would make me high and kill a few more of what little brain cells I have left, while my 1980 V8 would simply kill me
Standard, The EU6 AE31 shouldn’t be smelling at all at any time. I can start mine and have a sniff when it’s just started from cold or super hot and not detect anything, and I’ve still a keen sense of smell, even though the eyes and lugs ain’t what they were.
If you don’t have a decent OBD reader, for peace of mind I’d advise taking it to an AMLMD for ignition and fuelling diagnostics and gas analysis. I’d be hopeful it’s something trivial, like a dodgy batch of fuel or maybe old fuel? - but if not, and the exhaust hasn’t been modified, it could be anything from blocked filters to failing coil packs to oxygen sensor and damaged catalysts.
Of mine, I feel I could almost breathe the gas coming out the back of the DB11, yours should be that clean. My modified V8VS would make me high and kill a few more of what little brain cells I have left, while my 1980 V8 would simply kill me
I'm the first owner and the exhaust is stock, with no modifications at all. However there is some history - the O2 sensor was replaced, then the whole engine got replaced (due to a faulty intercooler and leaking coolant into the engine). So basically the engine is brand new, but the catalytic converters are the same and have now 35k on the clock. Let me schedule a real diagnostics session to watch the parameters you recommended. Thanks.
Just to clarify - the car does not smell when idle, and when it is started it smells like any other gas car with cold catalytic converters, it settles when they are up to operating temperature.
What do you mean by the blocked filters?
Just to clarify - the car does not smell when idle, and when it is started it smells like any other gas car with cold catalytic converters, it settles when they are up to operating temperature.
What do you mean by the blocked filters?
Edited by ress on Saturday 11th February 12:37
Update - we measured the oil consumption, which revealed quite a high volume, around 0.7l per 1000 km. Further inspection showed oily spark plugs (no issue with turbochargers, I'm waiting for more details). The factory has decided to replace the engine. I'm curious what more details would be shared because the exhaust smell was present from the beginning so it could be faulty assembly or something like that.
ress said:
Update - we measured the oil consumption, which revealed quite a high volume, around 0.7l per 1000 km. Further inspection showed oily spark plugs (no issue with turbochargers, I'm waiting for more details). The factory has decided to replace the engine. I'm curious what more details would be shared because the exhaust smell was present from the beginning so it could be faulty assembly or something like that.
TarquinMX5 said:
Two engines in 35,000km (c22,000 miles), that's not good (statement of the bl**din' obvious).
I can't see how it would affect the current engine but, depending how bad it was, I wonder if the coolant leak into the previous engine damaged the cats?
Yes but did you previously, and are you this time, getting a NEW engine?I can't see how it would affect the current engine but, depending how bad it was, I wonder if the coolant leak into the previous engine damaged the cats?
When my Vantage S engine was replaced under warranty at 20K miles I was told I was getting a "new" engine. Somewhat ridiculous anyway because the only fault was the valve shims going out of spec. but the main dealers do not do any internal engine repairs, instead they just put a "new" engine in. Turns out that "new" engine is a remanufactured engine and mine was of dubious quality. The value shims went out of spec. again within a couple of years and so I had the repair done by an independent that actually works on engines.
The killer blow came 5 years later when that engine had done 30K miles and dropped an exhaust valve head into cylinder 2. The resultant catastrophic engine failure is the subject of another thread that I will update shortly https://www.pistonheads.com/gassing/topic.asp?h=0&... but suffice to say it almost broke my resolve to own a nice car.
My point is, you're probably not getting a NEW engine, just as you didn't last time, and perhaps that's why it's failed again so quickly. "Luxury" doesn't necessarily equal quality I'm afraid.
TarquinMX5 said:
Two engines in 35,000km (c22,000 miles), that's not good (statement of the bl**din' obvious).
I can't see how it would affect the current engine but, depending how bad it was, I wonder if the coolant leak into the previous engine damaged the cats?
Good point. I have asked for the cats analysis but who knows? At the moment, I completely lost trust in the brand and dealer (and bought 911 just because of the fact it is produced in mass quantities, has fewer issues, and there are quite a few experts/services in my area).I can't see how it would affect the current engine but, depending how bad it was, I wonder if the coolant leak into the previous engine damaged the cats?
V8V Pete said:
My point is, you're probably not getting a NEW engine, just as you didn't last time, and perhaps that's why it's failed again so quickly. "Luxury" doesn't necessarily equal quality I'm afraid.
There could be something about this, let me try to get more insight but I doubt they would admit it.Owning the same cars with the same engines as both ress and Pete I begin to wonder if I’m walking a tightrope…
A common factor between the two cars here is early life faults followed by factory ‘replacement’, which is subsequently followed by further engine failure requiring replacement/rebuild. OK different failure modes, catastrophic in Pete’s case and what looks like internal wear or component failure leading to excessive oil consumption in ress’s case…
So I read that OP ress eventually concluded the smells to be burning oil. Before better engine design, manufacturing and better oils and component longevity AND multi-cats made oil burning both a much rarer and harder to detect thing, it used to be easy to see if you were burning oil - the smoke where visible would have a blue tinge.
Excessive oil consumption, bad luck, it looks very much like your ‘replacement’ engine was flawed from the outset. 0.7litre or more than a pint every 600miles (1000km) is indeed heavy oil consumption for any engine, let alone one as modern as that V12. By comparison, I could not detect any noticeable consumption with mine in between oil changes, which I’d consider to be the norm.
In the good old days, heavy oil consumption, smoky/smelly engines would usually be down to bore wear or valve stem seals, sometimes blown turbos on later designs, though there are myriad other and less serious/detectable and fixable sources, for example the old AML n/a V12 could slurp oil as a result of a failed breather valve.
Excessive oil consumption is a very bad thing, due in part to the fact that in general modern cars are so good, and systems so automated that many owners no longer properly check the engine oil as often as they should, and if excessive consumption is not detected and temporarily resolved (by adding more oil), the risk of serious internal engine damage and catastrophic failure shoots up. Thankfully the AE31 retains a good old dipstick.
I guess as you are getting another ‘new’ engine and are moving to a 911 you probably aren’t that interested in determining the root cause of this second failure - but many of us in here absolutely would be…
While it’s clear you have lost faith with AML products, and very sorry to hear that, respectfully, is there any chance that you can request that out of courtesy they update you with the established root cause failure mode of your failed engine (it will happen as the lump will likely go for strip (maybe) root cause analysis and rebuild at AM’s new AE31 V12 engine build subcontractor, Autocraft UK. I feel pretty sure that whoever is having to underwrite yet another engine replacement will want at least some answers…
It would be helpful for us here on the forum, as owners of similar cars to understand as much as possible about what has gone wrong.
It appears that you have had terrible luck. AM engines are generally considered to be very tough. Until now I’ve not heard of a single failure of the AE31 V12. Remember also that Porsche engines also have their fair share of problems.
Finally - are you 100% sure that they repaired your original fault (intercooler failure) by replacing the entire engine?
The subsequent problems you have described and have now been confirmed to be (engine component wear resulting in) excessive oil consumption could present to some people as both a continuation and development of the original problem.
I wish you the best of luck, and if you can, please update us all
A common factor between the two cars here is early life faults followed by factory ‘replacement’, which is subsequently followed by further engine failure requiring replacement/rebuild. OK different failure modes, catastrophic in Pete’s case and what looks like internal wear or component failure leading to excessive oil consumption in ress’s case…
So I read that OP ress eventually concluded the smells to be burning oil. Before better engine design, manufacturing and better oils and component longevity AND multi-cats made oil burning both a much rarer and harder to detect thing, it used to be easy to see if you were burning oil - the smoke where visible would have a blue tinge.
Excessive oil consumption, bad luck, it looks very much like your ‘replacement’ engine was flawed from the outset. 0.7litre or more than a pint every 600miles (1000km) is indeed heavy oil consumption for any engine, let alone one as modern as that V12. By comparison, I could not detect any noticeable consumption with mine in between oil changes, which I’d consider to be the norm.
In the good old days, heavy oil consumption, smoky/smelly engines would usually be down to bore wear or valve stem seals, sometimes blown turbos on later designs, though there are myriad other and less serious/detectable and fixable sources, for example the old AML n/a V12 could slurp oil as a result of a failed breather valve.
Excessive oil consumption is a very bad thing, due in part to the fact that in general modern cars are so good, and systems so automated that many owners no longer properly check the engine oil as often as they should, and if excessive consumption is not detected and temporarily resolved (by adding more oil), the risk of serious internal engine damage and catastrophic failure shoots up. Thankfully the AE31 retains a good old dipstick.
I guess as you are getting another ‘new’ engine and are moving to a 911 you probably aren’t that interested in determining the root cause of this second failure - but many of us in here absolutely would be…
While it’s clear you have lost faith with AML products, and very sorry to hear that, respectfully, is there any chance that you can request that out of courtesy they update you with the established root cause failure mode of your failed engine (it will happen as the lump will likely go for strip (maybe) root cause analysis and rebuild at AM’s new AE31 V12 engine build subcontractor, Autocraft UK. I feel pretty sure that whoever is having to underwrite yet another engine replacement will want at least some answers…
It would be helpful for us here on the forum, as owners of similar cars to understand as much as possible about what has gone wrong.
It appears that you have had terrible luck. AM engines are generally considered to be very tough. Until now I’ve not heard of a single failure of the AE31 V12. Remember also that Porsche engines also have their fair share of problems.
Finally - are you 100% sure that they repaired your original fault (intercooler failure) by replacing the entire engine?
The subsequent problems you have described and have now been confirmed to be (engine component wear resulting in) excessive oil consumption could present to some people as both a continuation and development of the original problem.
I wish you the best of luck, and if you can, please update us all
Edited by Calinours on Saturday 16th December 10:07
Calinours, thanks much for your message. Here are some answers.
Calinours said:
Excessive oil consumption, bad luck, it looks very much like your ‘replacement’ engine was flawed from the outset. 0.7litre or more than a pint every 600miles (1000km) is indeed heavy oil consumption for any engine, let alone one as modern as that V12. By comparison, I could not detect any noticeable consumption with mine in between oil changes, which I’d consider to be the norm.
Same view here, the second engine must be flawed from the beginning. The original engine with the faulty intercooler hardly consumed any oil, something around 0.1 liters per 1000 km.Calinours said:
I guess as you are getting another ‘new’ engine and are moving to a 911 you probably aren’t that interested in determining the root cause of this second failure - but many of us in here absolutely would be…
While it’s clear you have lost faith with AML products, and very sorry to hear that, respectfully, is there any chance that you can request that out of courtesy they update you with the established root cause failure mode of your failed engine (it will happen as the lump will likely go for strip (maybe) root cause analysis and rebuild at AM’s new AE31 V12 engine build subcontractor, Autocraft UK. I feel pretty sure that whoever is having to underwrite yet another engine replacement will want at least some answers…
It would be helpful for us here on the forum, as owners of similar cars to understand as much as possible about what has gone wrong.
911 is now my daily, but Aston remains in the garage, it sits in my heart and still will provide much more emotions compared to the 911. I'm interested in understanding the root cause and I will keep you posted.While it’s clear you have lost faith with AML products, and very sorry to hear that, respectfully, is there any chance that you can request that out of courtesy they update you with the established root cause failure mode of your failed engine (it will happen as the lump will likely go for strip (maybe) root cause analysis and rebuild at AM’s new AE31 V12 engine build subcontractor, Autocraft UK. I feel pretty sure that whoever is having to underwrite yet another engine replacement will want at least some answers…
It would be helpful for us here on the forum, as owners of similar cars to understand as much as possible about what has gone wrong.
Calinours said:
Finally - are you 100% sure that they repaired your original fault (intercooler failure) by replacing the entire engine?
100% sure, I have seen (and took a photo) of the old engine in a crate box.Ah, OK. It would seem then that the new engine may have had a problem from the outset, or insufficient care was taken with the installation of the replacement engine. I’m assuming the failed heat exchanger was replaced and all connecting pipe work cleaned when that engine was installed…
Cleanliness is critical, with the best will in the world no garage/workshop could reproduce the control the factory would exercise over this.
I’ve gone from hearing of zero AE31 engine failures/replacements before today to now hearing of two - and you are the owner of both, crumbs. A similar story to last year when V8S engine failures alarmingly started being reported (like Pete’s).
Thanks for the reply and I’m sure many will look forward to your update.
Cleanliness is critical, with the best will in the world no garage/workshop could reproduce the control the factory would exercise over this.
I’ve gone from hearing of zero AE31 engine failures/replacements before today to now hearing of two - and you are the owner of both, crumbs. A similar story to last year when V8S engine failures alarmingly started being reported (like Pete’s).
Thanks for the reply and I’m sure many will look forward to your update.
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