[vLiiaaM]

Hello,

Hoping to get a little bit of guidance.

My A1 has been rough idling on start, regardless if cold or warm. I got an EML with the code P2188 - system too rich at idle bank 1. There was a strong smell of fuel mixed with the oil and oil level was high. I decided to change the piston and seals on the HPFP, but didn't make any difference. So I took my car to a local garage and they found fuel trims were out. Spark plugs and injectors were all fine, compression normal. But they did note that one pipe in the intake system had 'come adrift'. They reconnected this and changed the oil, cleaned the injectors through and the fuel trims were now correct. After about two weeks, rough idling started again but was less frequent. As the car was driven more, the rough idling became more frequent.

I decided to take it to another garage to have a second opinion; they found the oil was a little high again but thought little of this. They checked the fuel trims and noted these as higher than they should be again. They focused on the injectors, checked the bores, removed spark plugs and didn't smell any petrol. Misfire counter showed various cylinders logging misfires on start, but not whilst running/driving. They did a full carbon clean, and advised to give it a good run to clear out any loose carbon leftover (there was a lot!). Was advised to use E5 fuel (premium) and run it through.

The rough idles are still occurring as frequently as before, and once again I have an EML with error code P2188 - system too rich at idle bank 1, and code 04106 - manufacturer specific. Oil is extremely potent with fuel and the level is way above the maximum line on the dipstick.

Does anyone have any ideas what else could be causing this issue/seen anything like this before? I will be taking the car to an Audi Specialist next week in hopes of some further diagnostic and a resolution.
Any help would be much appreciated!

 

[amonkeymafia]

Hi,

That sounds like a painful one to work out as crankcase fuel dilution causes listed below...

So what makes it difficult is there is not one cause of fuel dilution within engine oils and this is a reason why it is such a common occurrence within engines. However, the main cause is through a process called blow-by. This occurs because most seals are not perfect (nor are the cylinders perfectly rounded), or there is an opening through the cylinder crosshatches, and this causes the migration of fuel and exhaust gases into the areas where the oil is used. This often happens in the region between the piston rings and the cylinder bore.
But it is worth noting that other factors include leaking of the fuel injectors, incomplete combustion of the fuel, low engine temperatures, long periods of idle time and frequent short-distance driving. Below, we look at some of the other factors and mechanisms that contribute to fuel dilution in engine oils.

Wet Stacking
Wet stacking occurs in engines which are cold, i.e. engines that have not yet reached their optimum operating temperature. Colder engines have a lower combustion efficiency than engines which are at the ideal operating temperature, and this causes the fuel to ignite further on in the compression stroke (because of the lower internal temperatures). This can also cause the fuel coming out of the injector to stick to the walls of the cylinder. Once the fuel is stuck to the sides, it will slowly enter the oil system by being scraped off by the piston rings and entering the crankcase.
Poor Maintenance
Fuel dilution within an oil system happens slowly. So, when some oil becomes contaminated with a small amount of fuel, the effects are very minimal and won’t affect the performance of the oil (or the engine in general). That is if it isn’t allowed to build up—that is when issues start to arise as large amounts of fuel dilution will affect the performance of the oil and the engine. Therefore, regular maintenance in the form of regular oil checks and changes can stop fuel dilution from presenting any adverse effects, but there can be catastrophic consequences if these basic checks are ignored.
As well as regular oil checks and changes, checking the fuel injector nozzles can help to reduce the occurrence of fuel dilution—as dirty nozzles can prevent the fuel from atomizing correctly, and in turn, prevent the fuel from combusting efficiently—so not keeping up with maintenance in this area is another way of increasing the potential for fuel dilution to occur.
Engine Modifications
Modifications to an engine, especially anything that affects the way that fuel is injected into an engine, is another way of increasing the possibility of fuel dilution within the engine oil. This is often manifested through modifications that produce a much greater amount of smoke. The smoke passes by the crankcase before leaving via the tailpipe, so naturally, more smoke is going to enter the oil system which causes the oil to be diluted by the fuel; as well introducing other types of oil contamination.
The Implications of Fuel Dilution in Engine Oil
There are quite a few concerns with fuel dilution which affect the performance of the oil and the engine in general. Over time, excessive dilution can lead to a significant amount of wear, and ultimately, the failure of the engine.
The biggest issue that arises from fuel dilution is the lowering of the oil’s viscosity, as fuel has a much lower viscosity than the oil (as well as possessing a lower vapor pressure and thinning effect), which in turn can cause the oil-fuel mixture to adopt a viscosity lower than it is designed for. This causes the oil to possess less-effective lubricating properties and causes the strength of the oil film to be reduced, which increases the amount of wear on the cylinder liner and the bearings—this arises from the fact that the oil film is crucial for reducing the friction between moving components by providing a barrier, and the thinning of the oil causes the effectiveness of the barrier to be reduced, thus increasing the amount of wear on the system.
There are also many other issues that can occur because of a lower oil viscosity (or a degraded oil in general), and these include reducing the effectiveness of the additives within the oil, increasing the volatility of the oil and increasing the rate at which oxidation occurs within the oil (which then leads to more frequent oil changes).

Please let me know how you get on ;-)

M

 

[DavidC_Surrey]

Hi,
I've also looked at this car and having viewed a few cut-away drawings of the engine, I was convinced that it had to be the HPFP despite the first mechanic telling the owner that it couldn't possibly be that. There is literally a hole in the rocker cover which it is connected to, with a lobe of the cam shaft driving a piston to pump the petrol into the injector bar. I couldn't see any other way that so much petrol could be ending up in the oil, that the level rose up to the red warning marker on the dipstick in a little over a week or two at most. A stuck injector would result in unburnt fuel in the cylinder which could pass the pistons into the crank case but one of the mechanics who had seen the car did compression tests which he reported were fine. He also said that the injectors tested fine and were not stuck open or closed. The owner also put so much injector cleaner through the engine that it is probably gleaming like a mirror in there now 😄 I believe that the large quantity of fuel in the oil was causing the rich fuel mixture, by coming back up past the pistons in the oil film and that the HPFP had a leak somewhere inside resulting in fuel leaking directly into the rocker cover. I was confused initially when replacing the outer seal and cam follower "piston"-like thing didn't fix it and we ordered up a brand new HPFP which I fitted. The oil level is no longer rising after a couple of weeks plus now and we believe that the problem has been resolved.
I'd like to open up the old pump to see if whatever caused this is visually apparent and if it could be repaired rather than members here having to for out over £200 for a new pump.

I do find it quite worrying that the three separate professional mechanics who have looked at this car, were unable to work that out but were able to find various ways of spending a couple of thousand Pounds of the owner's money! 🙄 I hasten to add, though, that the third garage didn't charge at all so full marks to them, and in fairness they looked at the car after I'd fixed it, not yet knowing that it was fixed.

I personally believe that the transient misfire on startup is a different, unrelated matter. Could be down to the rich mixture from reverse blow-by I suppose, as it has improved recently now that's fixed. It could be a coil that doesn't like being cold or a similarly minded injector or spark plug. I think we're going to stop worrying about that now. Or it couild be an improving residual effect of a car that laid idle for nearly two years before the current owner acquired it.

 

[IvorETower]

Hi,
I've also looked at this car (snip)
Or it could be an improving residual effect of a car that laid idle for nearly two years before the current owner acquired it.

I wish we'd known that before ! It seems that very many problems can be caused by laying a car up for an extended period of time.
Fingers crossed that the issues have all now been resolved to the current owner's satisfaction

 

[DavidC_Surrey]

I wish we'd known that before ! It seems that very many problems can be caused by laying a car up for an extended period of time.
Fingers crossed that the issues have all now been resolved to the current owner's satisfaction

Yes indeed. My own Jaguar also suffered quite badly from being unused throughout the pandemic. All sorts of annoyances now!

Thanks for the help and advice in here. I'm sure one of us will get back to you should there be any further information.

Incidentally, having seen the A1 when it came back from the initial oil change, I know that the oil was at the correct level then. When I changed the oil finally myself, when it was well up the warning marker, I drained out almost a Litre of extra fluid than was supposed to be in there! 😲

 

[Riohindle88]

Hello David,

I've just seen this Audi A1 forum, which my Audi A1 TFSI 1.4 S Line is experiencing the same issue.

Taken the car to multiple garages and none of them can diagnose the fault, the initial mechanic advised the Oil had been overfilled which makes sense if the issue you've mentioned is related to the fuel pump.

Do you have any contact details you can provide me to speak to you

 

[DavidC_Surrey]

Hi, I have sent you a text if you need to call me. In a nutshell, though, we took the car to three garages to find out what was going on and I'd already pretty much decided that the HPFP was the problem despite one garage (supposedly an Audi specialist) telling me it couldn't possibly be that. As I think I mentioned; I initially replaced the piston and seal but it still did it and that was when we decided to take it to a professional but it was a complete waste of £1000 or more for various mechanics to try to diagnose it. That was when I got hold of an engine diagram and had a look to see what was going on and I realised that there was only one place that fuel could be getting into the oil in that sort of quantity and that was the HPFP. So I replaced the whole thing and that was problem solved. Still now, months later, the oil level has not risen. It was an incredibly easy part to replace, too.

 

[Sillystu84]

Hi, I have sent you a text if you need to call me. In a nutshell, though, we took the car to three garages to find out what was going on and I'd already pretty much decided that the HPFP was the problem despite one garage (supposedly an Audi specialist) telling me it couldn't possibly be that. As I think I mentioned; I initially replaced the piston and seal but it still did it and that was when we decided to take it to a professional but it was a complete waste of £1000 or more for various mechanics to try to diagnose it. That was when I got hold of an engine diagram and had a look to see what was going on and I realised that there was only one place that fuel could be getting into the oil in that sort of quantity and that was the HPFP. So I replaced the whole thing and that was problem solved. Still now, months later, the oil level has not risen. It was an incredibly easy part to replace, too.

Hi I’m having same issue with a vw golf 1.4 tsi it failed mot on emissions and really strong smell of fuel when opening oil filler cap, had oil pressure warning but nothing else, to me there is petrol getting into oil could this be the hpfp ?

 

[keviskennogti6]

I am too having the same problems with my daughters car, Audi A1 1.4 TFSi, where & which one did you get please?