Dude bin in the trade for years just haven't done much on these r have a vcds.....
A3 performance issues please help
- Thread starter Zman6000
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He mentioned using one of a previous car not this one... but no, MBC is not really the best idea...
<tuffty/>
The only thing that bugs me is these codes were not there until the decat? Put cat back on no boost issues? Changing back to standard map makes no difference unless the cats on? So either map doesn't affect it only the decat pipe just thought you guys would of come across this a lot like I do cambelts and clutches and mots daily :sYes...
Just lucky I guess
<tuffty/>
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MAF's go all the time... I got through 3 in 18 months... last one was for a couple of years...
It needs to be treated as a service part and if you don't know when it was changed its worth doing anyway
<tuffty/>
It needs to be treated as a service part and if you don't know when it was changed its worth doing anyway
<tuffty/>
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MAF signal too low fault from my experience is a faulty MAF... MAF determines load for the ECU... the map will be in the wrong load areas if under reading and will try and create more boost to achieve requested load... this is most likely whats causing the overboost fault
<tuffty/>
<tuffty/>
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tbh mate it needs logging on a dyno and checking over by a specialist at this point...
If you are now sure that the engine and all its required sensors etc are sound, that you have no leaks etc then the only things that generally creates over boost is a faulty N75 or actuator..
You need to determine what the map is asking the hardware to do so needs to be logged under load in VCDS to see what the boost request vs actual is, log N75 duty to see how its dealing with it...
The other thing to try (not sure if I mentioned this previously) is to unplug the N75 electrically and get a baseline on the boost... the actuator is mechanical so should be at a baseline boost pressure which is around 5psi iirc... if this is correct then its would potentially rule out the actuator... N75 will still operate when faulty, its the valving that fails so if you can swap it out with a known working one that would potentially eliminate that as the issue... have check quite a few in the past, symptoms ironically are boost spikes...
If the map is requesting the right amount of boost but the actual boost is way higher for too long this will cause limp mode... this is why you need to log the car to establish what it is you are working with... if its a typical generic map it maybe that they have just lifted the load tables too high and its requesting all the boost... this is not a good way to map by the way...
Not much else I can suggest other than this as you are blind without logging at this point
<tuffty/>
If you are now sure that the engine and all its required sensors etc are sound, that you have no leaks etc then the only things that generally creates over boost is a faulty N75 or actuator..
You need to determine what the map is asking the hardware to do so needs to be logged under load in VCDS to see what the boost request vs actual is, log N75 duty to see how its dealing with it...
The other thing to try (not sure if I mentioned this previously) is to unplug the N75 electrically and get a baseline on the boost... the actuator is mechanical so should be at a baseline boost pressure which is around 5psi iirc... if this is correct then its would potentially rule out the actuator... N75 will still operate when faulty, its the valving that fails so if you can swap it out with a known working one that would potentially eliminate that as the issue... have check quite a few in the past, symptoms ironically are boost spikes...
If the map is requesting the right amount of boost but the actual boost is way higher for too long this will cause limp mode... this is why you need to log the car to establish what it is you are working with... if its a typical generic map it maybe that they have just lifted the load tables too high and its requesting all the boost... this is not a good way to map by the way...
Not much else I can suggest other than this as you are blind without logging at this point
<tuffty/>
Need someone who can check this then but rang MRC tuning they said they don't do this engine anymore? They recommended badger5 but I'm sure he's miles away from Stafford?
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People have travelled from Scotland and even Norway to get to Bill's...
Badger 5 is around 90 miles from Stafford...
<tuffty/>
Badger 5 is around 90 miles from Stafford...
<tuffty/>
Disconnect the n75 valve 5psi no overboost only wastegate pressure could be a faulty n75 what dya reckon?
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Can't rule it out as I have seen it happen a number of times while Bill has been mapping cars....
If you know of someone with a 1.8t you could borrow the N75 from to try it rather than keep buying bits... I couldn't say for sure that it is the N75 but my normal diagnosis process would be to try one as I know they can cause this type of issue...
<tuffty/>
Yeah we'll am going to send the maf straight back the price of that lol may just order n75 Ebay £39 doesn't have to be genuine does it?
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Personally I'd use a genuine one... pretty sure they aren't that much different to that from TPS... main reason is response time of the N75... its the reason the much discussed 'J' valve is supposed to be a 'performance' upgrade when the reality it all it does is slow the response of the actuator for a given duty from the ECU... it catches the ECU out on spool giving an overboost spike until the ECU catches up with itself and drops duty to regain control of boost... this excursion into overboost on older AGU engined cars with dumbass ME3.8 ECU's was manageable but on ME7 and above the ECU gets more upset with the overboost and will drop into limp...
The change in characteristics can be mapped around with custom mapping, Bill does this all the time but if not mapped for it chances are you will have similar issues to what you have now...
As for the MAF... the fact you got the MAF fault code suggests its still faulty... it may not have fixed the issue but I wouldn't be quick to return it..
MAF signal too low is a faulty MAF... I assume that fault code hasn't returned since fitting? just the over boost one?
<tuffty/>
Fitted new one cleared codes went for a drive did it immediately so went back and checked codes same 3 codes so I guess whatever the fault is, it's tricking the ecu to thinking the maf is faulty? So just fitted the old one back to see if there was any performance difference which there wasn't. Best bet is to get to bill let him work his magic to see if we can sort this ASAP as it's really annoying especially when I fix everyone else's cars no probs lol
Just thought I'd say with the n75 disconnected it had abit more vacuum on idle? Not sure if this gives a clue to anything
