S3(8P2): Misfire cylinder 3, no engine code faults - idles like a pig

[warren_S5]

Very strange, without warning the car starting running like a dog today (now I need a clutch and flywheel).

Started to feel incredibly hesitant, almost like it would cut out, then started to idle better but not well.

Car still very fast right to the redline but sounds pretty poor.

Ran diagnostics - no engine code errors were detected. Only thing that seems different that I hadn't noticed before was when you come of the throttle I'm getting a strange pressure release sound from the exhaust that I've not noticed before (heard it in an enclosed area which accentuated the noise).

Don't a very short log of how the car is running, so would be grateful if anyone could have a look at the log file more me and interpret whether you can see anything unusual beyond the misfire in cylinder 3 (I can e-mail the file over - txt)

Many thanks in advance

Warren

 

[KRL]

****** hell unlucky mate. It seems to be issue after issue for you at the moment

PM the files over and I can have a look and do my best to help. I am off out in 10 minutes so I will probably not get a chance to look at them until tomorrow.

 

[warren_S5]

Cheers Krisitian

Here are a few photos of plugs so they don't look that bad. All cleaned and re-inserted and whilst its better its not 100%.

Plug from cylinder 3

Current NGK plug vs an old Bosch OEM plug (for comparison)

An attempt to see down into cylinder 3 (fail!!)

All appears well - everything connected up as normal

Always happens at a time when garages will be shutting for weekend!!

 

[Sarah's A3]

Oh sorry to hear you've got problems! I wont tease but do you you get it sorted soon! x

 

[warren_S5]

Oh sorry to hear you've got problems! I wont tease but do you you get it sorted soon! x

Cheers hun!

Car is smelling very rich so I wondering whether its over-fuelling. As soon as I cleaned the plugs down it has improved it a bit.

Hopefully the bill won't be Paddy-sized, but by the time I've had the clutch / DMF done, I may need WMI to get round this issue (+ other stuff), I'm reckoning on £2k (and get the RS4 regulator fitted at same time). Maybe I should just buy a new one as I want S&M bucket seats!!

 

[Sarah's A3]

Cheers hun!

Car is smelling very rich so I wondering whether its over-fuelling. As soon as I cleaned the plugs down it has improved it a bit.

Hopefully the bill won't be Paddy-sized, but by the time I've had the clutch / DMF done, I may need WMI to get round this issue (+ other stuff), I'm reckoning on £2k (and get the RS4 regulator fitted at same time). Maybe I should just buy a new one as I want S&M bucket seats!!

Ew! could be a dear do! Bucket seats eh!!! very tempting..........

 

[paddy]

Sorry to hear this warren. The fault codes are not comprehensive on Audi's, mine never did show a fault code although it registered a misfire on the vagcom blocks. If it was rich i would have thought the Lambda sensors would pick it up and in any case the plugs look fine. dont suppose you can hear an air leak anywhere around the intake...? try tapping the throttle body with a spanner in case its not shutting...other than that just run through blocks on the Vagcom and look for anything odd when comparing cylinders.

 

[warren_S5]

Sorry to hear this warren. The fault codes are not comprehensive on Audi's, mine never did show a fault code although it registered a misfire on the vagcom blocks. If it was rich i would have thought the Lambda sensors would pick it up and in any case the plugs look fine. dont suppose you can hear an air leak anywhere around the intake...? try tapping the throttle body with a spanner in case its not shutting...other than that just run through blocks on the Vagcom and look for anything odd when comparing cylinders.

WOuld you say in the comparison picture of the plugs Paddy that there is a lot of soot build up around the plug electrode (outer rim) almost like the plug which is 2 steps cooler is struggling to burn all the fuel (OEM plugs are 6's, one step colder which some run are 7's, and these are 8's which I was recommended to try when I was running OEM DP with Stg2+)?

 

[Iggu]

Don't know enough to help you for sure Warren but I was told only to run one step cooler NGKs (7s) by a number of people who know their VAG tuning. I've not had any problems like this but then again neither had you until today so who knows .... ? I was warned that 2 step cooler plugs might cause misfire problems though.

 

[warren_S5]

You may well be right Iggu.

I have some 6's/7's/8's in the drawer in the garage so I'll change to 7's.

I'm wondering if they are just too cold and there way too much unburned fuel in the chamber when running with richer mix on stage 2+.

Let's hope that's all it is as the car stinks of fuel at idle.

 

[Iggu]

You may well be right Iggu.

I have some 6's/7's/8's in the drawer in the garage so I'll change to 7's.

I'm wondering if they are just too cold and there way too much unburned fuel in the chamber when running with richer mix on stage 2+.

Let's hope that's all it is as the car stinks of fuel at idle.

Does stand to reason doesn't it ?
if so it's going to be a cheap fix and a big relief !

 

[warren_S5]

Does stand to reason doesn't it ?
if so it's going to be a cheap fix and a big relief !

You're not joking, would just wondering whether with all the carbonation that may have happened whether it's worth using any money I may save for WMI to repair some of the damage that may have been done.

 

[waring192]

You're not joking, would just wondering whether with all the carbonation that may have happened whether it's worth using any money I may save for WMI to repair some of the damage that may have been done.

Are you going to pop the sparks in tonight Warren?

 

[warren_S5]

Are you going to pop the sparks in tonight Warren?

was going to but I can't be @r$ed!! will do it in the morning and take it for a harsh run to clear it out. Just noticed lots of black spots on the back of the car like uinburned fuel so everything is pointing that way. As long as running new plugs can clear it through we should be laughing. If not, new car!!

 

[paddy]

Well to be honest you cant tell a lot from just looking at plugs like that. They can soot up very quickly if you have been running with a lumpy tick over for a while before taking them out. On the race bikes we used to do what was called a plug chop which involved running down the road at high revs and cutting the engine, coasting to a stop with the throttle shut and then checking the plugs. To be honest if it was rich it wouldn't be missing on one pot.

 

[warren_S5]

Well the good news is changing plugs has resolved the misfire issue, but as if often the case with Audi's you take one step forward and another backward.

Idle is now rock solid, but if you push on the brake pedal it starts to flutter. I take it this is an air leak!!!

Incidentally, changing to Iridium 6 plugs from Iridium 8's, the car feels slower at higher speeds even though the 8's were terrible at idle.

I'll give the week to be back in a position where all is good. No error codes, so zero point of going to Audi, so will have to be indpendent jobbie. Can see quite a few bits coming on the horizon, so maybe it is time for a change.

 

[jamieswales]

Mine seems to be having the same problem on idle, very lumpy idle with the occasional splutter. Runs fine when moving. Where can I get some of these plugs? Im not too sure what it already has as they I got the car with the stage2+ already fitted. Will try upload a video to show you what its doing and see if you can help.

 

[gaz m]

Don't know enough to help you for sure Warren but I was told only to run one step cooler NGKs (7s) by a number of people who know their VAG tuning. I've not had any problems like this but then again neither had you until today so who knows .... ? I was warned that 2 step cooler plugs might cause misfire problems though.

Iggu's right warren, Just one step colder should have you sorted mate.

There is a test we do on fuel called RVP (Reid Vapour Pressure) it is an estimate of the starting ability of the sample, so your fuel could have a low score and the cold plugs are defo not helping if you have excessive carbon as the fuel is not burning right.
It could just be that the last lot of fuel you got was near to the bottom of the garage's tank? Some smaller companys often mix storage tanks at the refinery as new stocks come in and so every so often they will mix old and new stock which actualy makes it all old stock!

Fuel only has 6 months before it starts to break down a bit and loose's some starting abilities even though it will still pass all the quality control test's. .......... It realy does pay to stick to a big company for fuel as quality control and additives are slightly higher quality.

Also the air leak when you put foot on the brakes wont help your tick over as the leak will come from the inlet manifold which may cause the ecu to use a wrong calculation for its fuel air ratio?

Gaz

 

[warren_S5]

Iggu's right warren, Just one step colder should have you sorted mate.

There is a test we do on fuel called RVP (Reid Vapour Pressure) it is an estimate of the starting ability of the sample, so your fuel could have a low score and the cold plugs are defo not helping if you have excessive carbon as the fuel is not burning right.
It could just be that the last lot of fuel you got was near to the bottom of the garage's tank? Some smaller companys often mix storage tanks at the refinery as new stocks come in and so every so often they will mix old and new stock which actualy makes it all old stock!

Fuel only has 6 months before it starts to break down a bit and loose's some starting abilities even though it will still pass all the quality control test's. .......... It realy does pay to stick to a big company for fuel as quality control and additives are slightly higher quality.

Also the air leak when you put foot on the brakes wont help your tick over as the leak will come from the inlet manifold which may cause the ecu to use a wrong calculation for its fuel air ratio?

Gaz

Gaz,

Interesting post,

I always use Shell V-Power 98 (one used half a tank of 95 in Cornwall 2 years ago when I nearly ran out of fuel). Used Shell V-100 in Germany for 1000+ miles.

Exhaust is black, and I mean coked BLACK!! When I accelerate I get a plume of black dust out of the exhaust where there must be massive carbon build up from the 8's (two steps colder).

Something is not right - have you seen my plug comparison thread of the 4 plugs types I've used?

Been meaning to get to Ben at AVP for about a month, but have had to cancel due to work commitments, will try and schedule a day soon as something seems wrong. Exhaust pops during cold start cycle when you lift off the power, and there is an odd noise coming from the exhaust as you life - almost a split second 'farty' type noise - no, it's not me ;-)

Again, no error codes to speak of, but with all that tech in the ECU there wouldn't be. Engine will fail before I get a useful DTC!!!

 

[warren_S5]

Mine seems to be having the same problem on idle, very lumpy idle with the occasional splutter. Runs fine when moving. Where can I get some of these plugs? Im not too sure what it already has as they I got the car with the stage2+ already fitted. Will try upload a video to show you what its doing and see if you can help.

e-bay / JKM Performance in Portmouth / sparkplugs.co.uk

 

[gaz m]

Warren

One thing we all overlook with the Audi's ECU is that it is ment to be adaptive so it may now have adapted its own settings to work with what it believes to be its current needs? Small air leak and cold plugs?

Does anybody know of a way to reset or revert to know ECU figures so that the changes you have now made will get a chance to work properly with good settings, or does the system constantly check itself so that it will sort itself out over a few hundred miles or so?

Just like Paddy I have spent years with bikes and it got to be an art sorting out fueling, Air ratio's and spark issue's. New plugs and a good long blast at higher rev's for an hour os so should clear out the exhaust! as a draw back of working on the car is excessive idle whilst you tinker away trying to sort the problem so excess carbon is produced.

Gaz

 

[gaz m]

Warren

One more point for you, I would recomend you also clean the EGR valve as if also clogged up with carbon it will stick open slighty and this may also be afecting the tickover as again the start figures for the ECU are wrong.

I would suggest "Jamieswales" tries to clean this as well or possibly fit a blanking plate which is what I have always done to all my past cars which have all been turbo's since I was about 20.

Hope you get sorted mate.

 

[willmac]

Seem to have heard a lot of people who have had Re-maps with idle issues etc, recently.
Not sure i would want to go that route now, but then again I suppose it is a low percentage of problems, versus those who have re-maps. But I am not the luckiest person in the world, so if anything is going to go wrong you can bet it will happen to me !

 

[gaz m]

Wilmac
Remaps make the car work a little bit harder so if a part is not up to standard or on it's way out it will just show up a bit sooner than it would normaly!
All the tuners check your car and take readings first and wont map the car until everything is ok according to vagco.

It is defo worth a bit of time whilst setting up the car for the reward you will get when it is set up properly!!!

Dont be put off as most of the S3's faults on here are very small and easy fixed compaired to the 3.2 threads and problems you can read as standard! (sorry guys)

Bite the bullet and go stage 2+ mate!

Gaz

 

[willmac]

Thanks for that Gaz,
Appreciate your comments. I don't want to be scared off, as the thought of that additional power is very tempting.
As you say , just need to make sure it is done professionally.
Cheers

 

[warren_S5]

Warren

One more point for you, I would recomend you also clean the EGR valve as if also clogged up with carbon it will stick open slighty and this may also be afecting the tickover as again the start figures for the ECU are wrong.

Your a star Gaz, many thanks for your help.

In the words of a true amateur (I'm embarrased to be asking this!!), where is the EGR valve - I bet it's somewhere awkward to get to! Can I do it over lunch, or do I have to take it to a garage and get them to do it. Reason I ask, is I'd thought with the full DP/exhaust system it may have gone. Take it that it will live somewhere nearer the turbo???

 

[KRL]

Warren
Does anybody know of a way to reset or revert to know ECU figures so that the changes you have now made will get a chance to work properly with good settings, or does the system constantly check itself so that it will sort itself out over a few hundred miles or so?
Gaz

A TBA (Throttle Body Allignment) with VCDS should do the trick or disconnecting the battery for 15 mins or so. Remember when disconnecting the battery that the REVO map settings will revert to stock.