problem with my s3 misfire??

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Rogue-24-84

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problem is my car has developed a misfire under acceleration, it runs fine on tick over 99% of the time but as soon as it comes onto boost it bucks and fu*ks about and runs aweful and with no power and a misfire, im baffled??!!


so ive now changed the plugs for new ones (iridium) new lambda - new fuel filter - new coil packs (gen audi) - new thermostat and maf changed.... still no better!! im pulling my hair out here, thats 200+ quids worth of parts and the problem is still here, and its showing up nothing on vagcom :(

anyone got any ideas?
 
Lean misfire maybe? had that before where the fuel pump is on its way out....

<tuffty/>
 
I hate issues like this, when did it start doing it ? were you driving it hard at the time or was it particularly wet outside etc ?

I would have said MAF initially but you say you have changed that already, was it a brand new one you fitted or if second hand was it known to be working ?

My next port of call would be to start looking for a boost leak somewhere.
 
Could be an air leak, or possibly engine is not seeing crank?? Vagcom would be first port of call!!!
 
it happened about 2 weeks ago

and no the maf was of a mates cars but worked the same with my one or his one.. do you think i should get a brand new one and try that?

to be fair when we first hooked it up onto vagcom it did come up and say knock sensor, but then that dissapeared and hasnt shown up again?? nothiung comes up on the computer now...
 
I had similiar problem, code thrown up was engine speed sensor signal implausible "intermittent".

New crank sensor fitted and boost a plenty............


rogo-24-84 said:
it happened about 2 weeks ago

and no the maf was of a mates cars but worked the same with my one or his one.. do you think i should get a brand new one and try that?

to be fair when we first hooked it up onto vagcom it did come up and say knock sensor, but then that dissapeared and hasnt shown up again?? nothiung comes up on the computer now...
Click to expand...
 
benh999 said:
I had similiar problem, code thrown up was engine speed sensor signal implausible "intermittent".

New crank sensor fitted and boost a plenty............
Click to expand...
Raelly!!! i said should we change it and he said no that wouldnt effect the misfire etc...... i will get one tomorrow and put it on, do you know where its located and if its hard to get to?? cheers
 
A Garage did it, someone will know the location though, usually close to the flywheel. If fault code has not reappeared then it could be something else. Please dont take my word as Gospel I dont profess to knowing S3 problems/solutions but thought I'd share my outcome of a similiar experience.

Ben:salute:
 
What engine code is your S3? all this expensive replacing of sensors etc won't just 'fix' a fault if you don't know what it is....

If you have a wideband ECU (AMK or BAM engine code) then log blocks 001 (lambda adjust), 031 (fuelling), and 115 (boost) initially...

Missfires like that are either fuelling or ignition related... you need to see what the fuelling is actually doing (going rich or lean) before throwing any more cash at the car..

<tuffty/>
 
If it threw a knock sensor code theres every chance that could be your issue as when the engine detects knock one of the things it will do is pull timing which would not cause a misfire as such but it would feel very similar. Does the S3 hit fuel cut when it detects excessive knock ? if so then that would also feel the way you are describing it which would also tie in with what tufty has said as it would effectively make it go lean due to cutting the fuel. Someone with more knowledge of the S3 ECU would be able to confirm if it does this or not, I know most map cars will do it.

As tuffty has said, don't just go throwing money at it until you properly diagnose the fault otherwise it could get very costly !
 
sideways steve said:
If it threw a knock sensor code theres every chance that could be your issue as when the engine detects knock one of the things it will do is pull timing which would not cause a misfire as such but it would feel very similar. Does the S3 hit fuel cut when it detects excessive knock ? if so then that would also feel the way you are describing it which would also tie in with what tufty has said as it would effectively make it go lean due to cutting the fuel. Someone with more knowledge of the S3 ECU would be able to confirm if it does this or not, I know most map cars will do it.

As tuffty has said, don't just go throwing money at it until you properly diagnose the fault otherwise it could get very costly !
Click to expand...

The way you just described is exactly what happened with mine. Turned out to be faulty knock sensor
 
sideways steve said:
If it threw a knock sensor code theres every chance that could be your issue as when the engine detects knock one of the things it will do is pull timing which would not cause a misfire as such but it would feel very similar. Does the S3 hit fuel cut when it detects excessive knock ? if so then that would also feel the way you are describing it which would also tie in with what tufty has said as it would effectively make it go lean due to cutting the fuel. Someone with more knowledge of the S3 ECU would be able to confirm if it does this or not, I know most map cars will do it.

As tuffty has said, don't just go throwing money at it until you properly diagnose the fault otherwise it could get very costly !
Click to expand...

Logging block 020 will show you the timing pull if knock is detected...

The ECU can pull up to 12 degrees of timing and something would need to be very wrong for this to happen... the ECU does not initiate fuel cut or boost cut on timing pull although it may do if it hits 12 deg of pull... never seen it so not sure what the reaction would be...

I would also check block 032 to see what the fuel trims are doing after a run... excessively high or low figures (more than 5-10% typically) suggests a problem although what depends on if its a positive or negative figure...

From what you describe it sounds fuel related either too rich or too lean...

<tuffty/>
 
Thanks for all your help, i dont know what id do without guys like you and places like this to get info from people that have had similar experiences/knowledge... i'l get it put back on the comp and see what its doing, i'l keep you posted :) thanks again


Ryan
 
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Another thing worth checking if you get nothing coming up on the computer is to check the wiring to the MAF. When I had my GTR I was suffering a misfire similar to what you described and through logging it with teh wideband it was going lean around 2500 - 3000 rpm but not all the time.

After much head scratching and messing about trying new MAF's etc I decided to pull back the outer sheath on the wiring harness to the maf to discover that the screen wire had broken through and was occasionally contacting the body of the car. I stripped it back and repaired it all then used heat shrink to protect the repair and the car ran perfectly once again !

This fault did not show on any diagnostic machine however it did show us as running lean which at least pointed me in the right direction.
 
<tuffty/> said:
What engine code is your S3? all this expensive replacing of sensors etc won't just 'fix' a fault if you don't know what it is....

If you have a wideband ECU (AMK or BAM engine code) then log blocks 001 (lambda adjust), 031 (fuelling), and 115 (boost) initially...

Missfires like that are either fuelling or ignition related... you need to see what the fuelling is actually doing (going rich or lean) before throwing any more cash at the car..

<tuffty/>
Click to expand...
mine's an apy engine, we now think its the knock sensor as it flashed up on the vagcom, but wont show up again??
 
i would be surprised if knock sensor wiring would cause misfires... has your fault gone if have fixed it?
you
 
<tuffty/> said:
Lean misfire maybe? had that before where the fuel pump is on its way out....

<tuffty/>
Click to expand...

My fuel pump is on its way out as its started to get noisey ....however in the last couple of weeks ive started getting ECU light flashing occassionally..... on checking codes im getting misfire codes coming up ...hence lean misfire....been taking it easy till im back to work so i can order a new one
This also happened on my mates mk4 golf gti too.....defo check your fuel pump
 
thanks i'l get that looked at, its really getting to me now.... just want the ****** thing sorted!!!
 
badger5 said:
i would be surprised if knock sensor wiring would cause misfires... has your fault gone if have fixed it?
you
Click to expand...
nope still doing it!! put a new thermostat in it the weekend as someone said they can cause issues and as they only cost like 7 quid i thought it'd be stupid not to eliminate it, also fitted a new lambda.... still no joy :(
 
WTF... does this sound firmilier? coz its weird.... right today i fitted a new fuel pump but when i started after it was still missing i just thought id drive it up to the bp to put some fuel in it as the light came on again, put £20 then drove it from bp to tesco about 7-8 miles and on the way it was missing worse than it has since the problem started, i jet washed the car and left it ticking over while i did it after id washed it i still left it ticking over while i shamied it over, but then as i pulled out of tesco i thought hmmm its not missing?! and then i didnt do it all the way home... and i just took it fr a 20 mile drive and it was pulling fine in every gear flew up to 110 like a rocket, and going better than it ever has since i bought it... what is going on with this car. could it of been an injector clogged? no doubt when i go back out to it later it'll be missing again.. :(
 
Have you had a compression test done on it bud?

Could be a sticky valve, if it's down on compression on 1 particular cylinder, get a cylinder leakage test done and it should show you which valve isn't seating right. That's if it is a valve...
 
sandip said:
Have you had a compression test done on it bud?

Could be a sticky valve, if it's down on compression on 1 particular cylinder, get a cylinder leakage test done and it should show you which valve isn't seating right. That's if it is a valve...
Click to expand...
yh i'l run it up the garage on monday, get them to have a butchers :)
 
audi upgrades
right so today i had the trottle body re calibrated after i took it off to clean it out, and its missing again!! had it but on vagcom and its saying lamda 1.. which has already been replaced (although not a genuine one but one that had to be spliced in, was half the price thats the only reason) we cleared all faults and ran vagcom again and the same fault came up!! ???? this never arose initially but is now, and it has a new one in it, could it have failed? before i take it back to motor parts and moan...
 
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That is unusual, although it's not completely unheard of for new parts to fail. What was the exact fault it was displaying?
 
lamba 1 intermitent, thats what the guy who vagcommed it was saying to me..
 
so today i pulled the wiring loom out and stripped back the black tape to reveal the wires to the coilpacks, this is what i found......... do you think this is my problem? arking out on eachother and the cam cover etc?

SDC11234.jpg
SDC11239.jpg
SDC11238.jpg
SDC11237.jpg
SDC11236.jpg

is this fixable? or do i need a new wiring loom?
 
Was just about to post that! Had terrible issues on mine for that! Some insulation and cloth tape and Problem solved!
 
Strip it all back as far as the N75 plug section in the harness and re-wrap, doesn't seem to go any further than that.
 
I am having similar issues can anyone give me any advice. At first it was just misfiring on idle changed the sparks plugs and coil packs and the misfire disappeared as well as the EML.

Misfire is back now but this time under load only not on idle. Any idea what could be causing this?

Cars getting a service tomorrow as I was told it might be the fuel filter at fault

Sent from my SM-G930F using Tapatalk
 
<tuffty/> said:
Any fault codes? what year of car? any mods?

<tuffty/>
Click to expand...
I posted in the wrong section I have a 8P but hopefully your still able to help.

59 plate. Stage 1 nap and only fault code was intermettient misfire cylinder 4. Cleared and hasn't come back but car still feels rough under post so I know it's misfiring

Sent from my SM-G930F using Tapatalk
 
Ah ok... prob better off in the 8p section then... fuel system is total different in 8L's

Only thing I know about the 8P fuel filter is that the pressure reg is built in for the low pressure side so its plausible if that playing up then it could over fuel but you need to get it logged on a dyno really

<tuffty/>
 
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