Misfire detection ?

AudiS3-Turbo

Registered User
Ive had this hesitation/stutter since upping the hp to revo stage two.

Ive fitted new plugs gapped to 0.7
Forge DV with uprated spring.
New ECT.
New Bosch maf
No air leaks

Im seeing 177mg/s from my air mass, disconnecting makes is slower but still the stutter is there,on light throttle and low rev range i cant feel it,higher up with my foot down it kangaroos/stutters.

No Fault codes but im trying to see if this is a misfire,ive trailed through all the measuring blocks of vcds 250 of them! and there is nothing there regarding misfire recognition?

I dont want to jump in the deep end with buying four new packs,by the way its an APY 2000,ive checked my wiring to the packs and there is nothing wrong with them.

any help would be great
 

Dani_B19

Audi-sports own special child.
Nice to see you back mate.

Any pics of the new car? You checked the coil pack loom? Recent threads on this have shown knackered wiring that have cost a few pound to fix buy just replacing the wiring, may be worth a try!
 

Dani_B19

Audi-sports own special child.
Sorry just read that youve already checked that lol.

No one local to swap packs with?
 

AudiS3-Turbo

Registered User
Cheers bud,no pics yet,will get some when its a sunny day....some time away lol ,My old s3 is now my mates down the road ha ha,but he is away for 3 weeks ...aaaggghh,would like it sorting before then.

So im assuming misfire detection is not applicable on pre 2001 s3?
 

Gops

Badger 5 Edition
VCDS Map User
Cheers bud,no pics yet,will get some when its a sunny day....some time away lol ,My old s3 is now my mates down the road ha ha,but he is away for 3 weeks ...aaaggghh,would like it sorting before then.

So im assuming misfire detection is not applicable on pre 2001 s3?

I think so because when my coilpack failed, it didn't show any faults!
 

Dani_B19

Audi-sports own special child.
Haha, just pop the bonnet and say chavs did it :) lol.

Dont think so mate, im chasing a A fault on mine and tbh it could be a missfire on idle! Mines also a apy! Yours got esp?
 

Dani_B19

Audi-sports own special child.
Think it might be something else mate. 177 is exteremly low, on my standard map i pulled 188.7 the other day.

No reason just wondered lol.

You sure theirs no leaks?
 

AudiS3-Turbo

Registered User
Yea its low,more with the new Maf tho ! Defo no leaks,pressurized intake system,no leaks bud,its low cos it can't boost higher up,got a mate who will lend me the later coils to try,see what that does.....fingers crossed :banghead:
 

Welly

335D Driver :-)
Yea its low,more with the new Maf tho ! Defo no leaks,pressurized intake system,no leaks bud,its low cos it can't boost higher up,got a mate who will lend me the later coils to try,see what that does.....fingers crossed :banghead:

Coils and MAF suspect here as said before - coils most likely for the misfire, however an underreading MAF will give you a potential lean condition.

What did the spark plugs you took out look like colour wise?
 

Jason.s

Registered User
Is this around 3k in 3rd perhaps? Or around that sort of area when booting it?
 

AudiS3-Turbo

Registered User
Coils and MAF suspect here as said before - coils most likely for the misfire, however an underreading MAF will give you a potential lean condition.

What did the spark plugs you took out look like colour wise?

Plugs looked good mate,nice light brown,but its hard to say as it runs fine low down, "normal" running, so by the time you take out the plugs you will see nothing,its a new Bosch maf and the part number is right for the APY motor so can but only hope its fine,but as i said before when its disconnected its lacking power as you aspect but it still stutters so im leaning toward the packs being weak as its got 145k on the clock,new ones from Audi will be ready to collect tomorrow so i will see what happens.

Annoyingly its not to bad tonight....
 

AudiS3-Turbo

Registered User
Is this around 3k in 3rd perhaps? Or around that sort of area when booting it?

Yea mate,more noticeable around then when you boot it,it will hesitate,then pull,hesitate again higher up and just hold back to red line.

I see you work for Audi/vw? is this known issue?
 

AudiS3-Turbo

Registered User
Well i fitted a set of genuine coil pack and as suspected they made no difference at all,after allot of reading on the net,revo maps seem to have a trend for showing up N75 valves and there is many many threads !

Next question to those in the know,what max boost pressure should i see with revo stage 2?
 

Jason.s

Registered User
Well its known when you search it on google but not really at a main dealer. My gf`s Leon Cupra does the same thing. Changed plugs, coils, serviced. The workshop controller suspects either a MAF or N75 valve.
 

fran-s3

Active Member
VCDS Map User
I had similar issues with my car when I had a remap. Changed everything as you said above - nothing. Ended up being the fuel pump! It was failing at higher rpm it couldn't pump enough fuel when needed. Was fine on ticke over normal cruising - no fault came up on VAG-COM either. Just have a look at your misfire's log on VAG-COM mine was misfiring in all cylinders on boost although I never knew it was a misfire when it was hesitating but that's what it actually was doing. Worth investigating. It was running lean and you they're are tell tale signs that it's the fuel pump if it's doing this.

1) Is your engine unusually hot after a run? (obviously all are - but mine was noticeably more you could fry an egg on it!) Sign that it's lean
2) Monitor the temperature on Air Con unit display is higher than 90 consistently? (google how to access this I can't remember how)
3) If it's been while it'll show on your exhaust tips! I know random eh - my exhaust tips were corroding badly around the edges badly because it was running so lean and the gasses make that happen apparently. APS showed me and they were right.

HTH.
 
Last edited:

Welly

335D Driver :-)
Have you checked the coil loom like Dani suggested? Really common for causing misfires.
 

Dani_B19

Audi-sports own special child.
How do you use vag com to check for mis fires?
 

Welly

335D Driver :-)
Later ECUs are better at it - they will normally pop a fault code.
 

Dani_B19

Audi-sports own special child.
So block 14 cylinder 1, 15 cylinder 2 and so on?
 

AudiS3-Turbo

Registered User
ok ive got an update,i adjusted my actuator a few more threads as my boost was not matching the requested,still no improvement, so out of desperation i disconnected the vac line from the DV and now the car is fine? thing is ive bypassed the n249 valve and the diverter valve when i fist got the car and it ran fine on stock ecu....the diveter valve is a 007 type that works just fine... it holds vacuum and does not open under boost,as the car is now "normal" with only the vac line disconnected.

So why the hell am i getting vacuum under 3/4/ full throttle runs thats opening my diverter valve???

Im i missing something here or have i gone mad?
 

Welly

335D Driver :-)
Is it just a straight vac line from the inlet mani to the DV?
 

AudiS3-Turbo

Registered User
just been out again,had it connect,bag o shi*t,disconected and fine.?


Do you think i could have a restriction in the intercooler or pipe work that could cause drag/vacum when foot flat? Saying that it goes fine with it disconnected so wtf!?

Edit...had the front off,checked both intercoolers and pipework...all clear.
 
Last edited:

AudiS3-Turbo

Registered User
im starting to think my intercoolers are a restriction,it still seem to lack "stage 2" power....

Also remembered a while bask there was testing and was found out that the TIP was imploding under full load....thats one thought?
 

Dani_B19

Audi-sports own special child.
What spring you running in the dv?
 

AudiS3-Turbo

Registered User
ive got two,black(std) and yellow,they make no difference which one you use,the fact is there is enough vacuum to open the diveter valve while on full or 3/4 throttle...?

Im going to do some more logs tomorrow,ive noted using my app on my phone im only seeing 140 via the air mass now,droped down from 170-190 with poor running.....im starting to get sick lol
 

Dani_B19

Audi-sports own special child.
Greens standard mate, they dont do a black, goes green, yellow, blue then red. Was going to say have you tried a spring but you have. Unsure why its dumping like it is, especially how you done the n249 delete as well.
 

AudiS3-Turbo

Registered User
Dani i dont know mate,ive stripped the front off to check intercoolers pipe work etc all looking good.

Ive logged air mass readings with my phone,with diverter disconnected im only seeing 140mg/s !!
Diverter conected im seeing 201mg/s and the car does go better fur sure but still has that stuttering..? but thats about right for this as the car is standard so i dont expect higher than that with stock intercooler,exhaust and air filter..

Ive swapped both diverter springs and no change,but its smooth as with it disconnected,im truly baffled ...

Im going to hook up a couple of pressure gauges on the diverter line and fuel pressure regulator as in theory i should be down on fuel pressure by 0.5bar if there is vacuum with throttle..

Thanks for your input Dani and the rest but looks like im just going to have to do trial and error to figure this out....why me? always my ****** car....ha ha
 

fran-s3

Active Member
VCDS Map User
Coils and MAF suspect here as said before - coils most likely for the misfire, however an underreading MAF will give you a potential lean condition.

What did the spark plugs you took out look like colour wise?

I always say this because it happened to me - but if running to lean check the fuel pump. (didn't register any fault code and was misfiring on all 4 cylinders on boost when mine was failing - fine off boost no startup issues - but when pushed when re-mapped it wasn't pumping enough fuel in hence the misfires) Worth a check - if bonnet is more hot than usual after a run would indicate running lead and fuel pump. You could literally fry an egg on mine after a run!
 
Last edited:
Top