After some help please if pos.

DaveS384

DaveS384

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Hi all, im just after some help with my S3. Its a pretty long story tbh so i wont go into it. Basically at when i put my foot down i get to about 4000rpms and it starts misfiring really bad.. Im not sure if its a boost problem on something else.

I have had new
Coil packs
N75 valve
Lambda sensor
Air maf
Map sensor
Vac pipes
TIP

i have also had it put on vagcom and nothing comes up when scanned.. The thing i wanted to ask you guys is, when i was playing round with it the other day i took the vac pipe off the top of the dump valve and didnt put it back on. then when i ran it down the road and the car ran fine just with less boost. I then put the vac pipe back on and the problem came back. so after a bit more playing i noticed that on tick over and light revs that top vac pipe sucks which i guess is normal, but if i rev it hard then that same vac pipe stops sucking and starts blowing.. so effectively im guessing that when driving the car with my foot down that top vac pipe must be blowing down on the piston.. now im not a mechanic and im not that great with engines.. can anyone please tell me A, if this is ment to happen or not? And if its not ment to do that then has anyone got any ideas as to what could be causing it and how i fix it??

i thank you all for reading and any help you can give me. This problem has been gettin me down for months now and i seem to spend all my time and money working on the s3 and not getting it fixed.. i have been to mechanics at several different garages and they all say something different.. then a guy on Facebook said that there are some very knowledgeable people on here so i thought i put a post up and see if anyone can help..

Thank you for reading

Dave
 
OK cool thanks pal! i just wanted to check so i can rule that out then.. ive got new injectors going in tomorrow coz someone told me that it could be clogged or bad injectors.. Thanks for the reply much appreciated :)
 
I don't know if I can, I'll have to have a look into that coz I do have my own VCDS but don't know how do fully use it.. I've only ran the standard diagnostic. I have logged certain blocks on it but not sure what all the block numbers are and what does what.. if that makes sense lol
 
Ok bare with me I'll go and do it now. Running but not driving yeah?
 
Ok cool I'm in the car now so bare with me
 
Ok so it says lambda -1.5% and voltage 5.700 V
 
taken from rosstech:
You can check your current state of trim by using VAG-COM or equivalent to look in Group 032 (in many modern ECU's, consult your Factory Repair Manual for the specific group for your particular vehicle) in your engine measuring blocks. The first two fields will have percentages. The first field tells the fuel trim at idle (Additive). The second field tells the fuel trim at elevated engine speeds (Multiplicative). Negative values indicate that the engine is running too rich and oxygen sensor control is therefore making it more lean by reducing the amount of time that the injectors are open. Positive values indicate that the engine is running too lean and oxygen sensor control is therefore making it richer by increasing the amount of time that the injectors are open.

It is totally normal for both the first and second fields to be something other than zero. In fact, zeros IN BOTH FIELDS indicates that either you just cleared codes (which will reset fuel trim values) or something isn't working properly. If values get too far away from zero, it will cause a DTC (fault code) and can set off the MIL (commonly referred to as the Check Engine Light, or CEL). Specifications for normal operation are usually somewhere near +/- 10%.

In general, an out-of-spec value in the first field (Additive) indicates a vacuum leak since it is mostly present at idle, when vacuum is highest. An out-of-spec value in the second field (Multiplicative) indicates a fault at higher RPM, and may point to a faulty MAF.
 
Ok so does that suggest a vacuum leak then? Sorry I'm pretty new to all this so learning as I go.
 
No idle trim is fine you may have to log it driving to get the second value or did it say + 5.7?
the second value is for when you are driving the car through the rev range, it is usually there just on ign ??
 
The second value just said 5.700 V then underneath the box it said voltage. Didn't have a + or -.. are the values ment to be lambda and voltage? Or have I done it wrong?
 
It will say - or for adding it will just say the number like so...

Error32
 
Ok mine didn't look like that when I did it.. think I must have done it wrong.. I'll have to do it again tomorrow Coz my missus is getting grumpy with me.. I cleared the codes about a week ago but it has had a good run since then..
 
audi upgrades
Nope. It had an air maf come up but got a new one and now it's all clear..
 
so when it misfires do you feel the car is shuddering and loosing power or just shuddering?
 
Both really mate, it shudders a bit and my boost gauge starts jumping around, goin from about 10psi to 20psi Just going up and down. Does that make sense?
 
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