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Wench
Original Poster
8 posts
74 months
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Hello,
I used to have a Mark 2 GTI 8V i rebuilt,but the other month i thought i'd try and get a sensible car... :-S
110 BHP Audi A3 which i brought yesterday. I have put 100 mile on it and today en route to work i lost power. Initially i thought i had a Turbo failure but no black smoke. This happened after driving approximately 15/20 miles down the motorway. On way home it did the same thing after about the same miles. So this evening i went for a little drive, after 30 miles again LHM initiated ( i assume it is limp home mode im noticing?). So far i have disconnected the MAF whilst it was in limp home and it made no difference. I then switched the ignition off and found this reset the LHM and then i unplugged the MAF, this gave me the say symptoms.
So after google and forum hunting i have come to the conclusion it could be one of the following. I'm a bit miffed as i've literally done just over 100 miles on my 'new' car.
1) Faulty MAF
2) N75
3) Boost Valve??
4) Turbo 'clogged'
5) Loose/broken vac hose
I'm gonna try and plug into a wigget VAG melarky thing tomoz but im concerned this will just say 'faulty MAF' and so not give me the real problem.
Ohh and who thought putting a Turbo behind the engine was a good idea?!?!
I also dont have a comic book for this car so i'm struggling to identify parts...any help and ways of eliminating diff parts would be greatly appreciated....
I did notice a comment put on in 2010 which say you can unplug the N75 and this should help diagnose somert but not sure what im looking for....
many thanks in advance
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Wench
Original Poster
8 posts
74 months
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Ok so now i'm even more confused... yesterday the audi was connected to the comp and it said that the cam rev sensor thingy was faulty. So today we went to fit a new sensor and found a completely different fault. Boost over pressure intermittent or somehting. We've tried to find the fault and have had no such luck. So i've just come back from a drive and cant get it to play up... anyone got any ideas how i can fault find this?
cheers
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shtu
527 posts
16 months
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Intermittent overboosting is usually related to the variable-geometry stuff in the turbocharger being jammed up with carbon.
Put some decent fuel in it and drive it like you stole it for a week. Lots of rpm, lots of wide-open throttle at all engine speeds. With a bit of luck you will be able to blow out a load of carbon and unstick the mechanism.
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Dr G
9,397 posts
112 months
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^^^ This is an easy one to eliminate and you can buy a spray in cleaner for the job too (not tried it myself but forum feedback is positive).
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Wench
Original Poster
8 posts
74 months
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Well after some investigation it only occurs when im on motorway normally in a high gear on load at around 2400 rpm..... Many forums have pointed at this N75 being sticky or like you said clogged up..
I'm planning to strip down (the car that is) this weekend and see if i can exercise and clean everything up....
He he he i always drive it like i stole it :-D ......
thanks
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Tame Technician
2,205 posts
74 months
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N75 is a simple electrical solonoid. The bit that is likely to be sticking in inside the turbo.
I put a big description on here about it before I try and find it.
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Tame Technician
2,205 posts
74 months
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shtu
527 posts
16 months
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Solid info in there.  As I say, cane it for a few days and you might get lucky with unsticking it.
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Wench
Original Poster
8 posts
74 months
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Thanks guys....
Plan A: Driven hard - check!! Fault less frequent, def LHM @ 2400 rpm in hogh gear,on load
Plan B: Strip Lines, Turbo etc down and clean (pray bolts comes loose/out)
Plan C: Cry and buy a new turbo.... :-D
So now onto Plan B fingers crossed for tomoz....
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Dactub
184 posts
10 months
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Hi I own a ibiza with the same engine and after I had it remapped it developed this at high revs though turn it off and back on and it's back to normal strange hope you get it sorted mate.
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Wench
Original Poster
8 posts
74 months
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Hey guys just though i'd give an update. Been driving high through gears and seems to have reduced the number of occurances. Also at the weekend i noticed there were a rather a lot of holes in my exhaust so replaced the cat part of the exhaust and i'll see how it goes....
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Wench
Original Poster
8 posts
74 months
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Ok so the fault has gone.. for now. I thought id write this up in case its of use to anyone else. All ive done is tested the N75 actuator by heating it up and blown through all the lines. I've also driven the car hard and replaced the cat... I suspect it was the N75 valve though...
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FraserLFA
4,934 posts
44 months
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Not sure if it's any help but my Focus is currently going in to LHM a lot and after diagnosis, it turned out to be the Throttle sensor.
Apparently a common fault with Transits, Fiesta's, BMW's and some Audi's.
Like I said, not sure if it's any help but thought i'd whack it up anyway.
EDIT: I believe the Audi/BMW issue can be related to faulty air flow meters on Diesel cars.
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TDIfurby
1,628 posts
45 months
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Italian tune up very good on diesels. Worth checking your EGR and intake manifold are not clagged up with soot too, with that mileage. Remove intake unit, and take a look inside around the flap, and also the entry to the intake manifold itself. If thats crappy its worth removing the whole manifold and cleaning it properly (air compressor and a lighter works well ) When rebuilding, get a thin piece of metal (two bits of drinks can work well) cut into the shape of where it bolts with two bolts to the exhaust manifold, and drill two holes, and seal between manifold and EGR pipe. Then there will be no recirculation of exhaust gases, but the EGR will still move and work how it thinks it should. Personally I have no EGR at all, but then I've gone a bit further with my derv than just a bit of tuning. 
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