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1.8T RUNNING ROUGH
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Bit of help guys please.

Ye wife's Got an A4 Avant 1.8T which has started hunting a bit on idle and running a bit rough just on idle. I took it for a drive and it pulls fine right through the rev range. From the bottom of second gear on WOT right round to about 6000 it's smooth, pulls well and you can hear the turbo spool ok.

However On overrun it seems to want to run on a bit. Additionally when the car is stationary revving it to 4000 rpm then releasing the throttle the rev's fall gradually for a couple of seconds before falling as they should back to idle. Idle then hunts between about 700 rpm to 1200 rpm and the engine is a bit rough....

Initially I thought Coil pack but they were all done about a year ago under warrenty and its not running on3 cylinders as it has done in the past when the coil packs went.

I'm gonna get it on vcds later tonight to check for any fault codes.

Any ideas?

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Strong Broo Racing

Boost leak.

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The Evo forum really is a shadow of its former self. I remember when the internet was for the elite and now they seem to let any spastic on.

IaFG Supercharged Muppet Division

I'd guess that you're leaking air somewhere in the inlet tract, past the throttle butterfly.

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Chief Wheel and Cake Monkey - Strong Broo Racing

Dirty MAF

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Something witty goes here.....

Jorg Gray Ltd Edition Watch Number : 313631

Vag-com should reveal all.

Cheapo cable off ebay will work fine with that year.

Diesel Taxi said...

Vag-com should reveal all.

Cheapo cable off ebay will work fine with that year.

Have got - needs an XP laptop so I'm going to borrow a laptop later.

--

Strong Broo Racing

VCDS-Lite Version: Release 1.0
Monday, 05 November 2012, 20:37:44.
Control Module Part Number: 8E0 909 518 AL
Component and/or Version: 1.8L R4/5VT 0003
Software Coding: 0011501
Work Shop Code: WSC 63251
4 Faults Found:
17705 - Pressure Drop between Turbo and Throttle Valve (check D.V.!)
P1297 - 001 - Upper Limit Exceeded
16684 - Shareware Version. To Decode all DTCs
P0300 - 008 - Please Register/Activate
16685 - Shareware Version. To Decode all DTCs
P0301 - 008 - Please Register/Activate
16686 - Cylinder 2: Misfire Detected
P0302 - 008 - Implausible Signal

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Strong Broo Racing

16686 - Cylinder 2: Misfire Detected sounds like coil pack unless it's an uncleared code from before.

The other points for n75 valve;

Here

Updated November 5, 2012 at 9:24 PM

Gonna have a proper look at the hoses tomorrow night in the workshop. Ill price up an N75 valve tomorrow also. I'm sure I've got a spare dump valve in the hut might try swapping.

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Strong Broo Racing

Back to basics but make sure the throttle body's clean, if it's built up a layer of crap the throttle flap might not be sealing properly when it's closed. This would make it hunt on idle, and so on.

Updated November 6, 2012 at 6:50 AM

ICV?

17705 is potentially the worst FLT code you could have!

It's a non specific boost leak anywhere in the system, I had it for most of the time I had my Golf 1.8T and never solved it after replacing I/C hoses, various vacuum hose and boost hoses, checking every hose clip, replacing the MAF, coilpacks, diverter valve, N75 valve, re-sealing the seconday air pump, cleaning and re-aligned the throttle body and just about anything else I could think of.

Common hoses that go are the small ones under and around the inlet manifold, also the big Y breather hoses that comes out the end of the rocker cover, they'd be the easiest to check first.

Another common one is the joint between the turbo outlet and the intercooler, it's a funny spring loaded metal push clip that can sometimes work loose, worth checking too.

You could be lucky and sort it out easily or most likely is that it'll be a real nightmare to track down.

Neat little trick for finding air leaks - can of brake cleaner and spray it methodically over each and every air hose you can find - when the leak is found the revs will go up as it ingests the brake cleaner.

:?:

If you have boost leaking out, why would it suck in anything?

I used soapy water and looked for bubbles.

--

The Evo forum really is a shadow of its former self. I remember when the internet was for the elite and now they seem to let any spastic on.

IaFG Supercharged Muppet Division

Engines suck, Dave, on boost or otherwise ;)

nefarious_ said...

I'd guess that you're leaking air somewhere in the inlet tract, past the throttle butterfly.

Yes this had something similar on an old Beemer years ago.

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BMW Car Magazine

JL said...

Engines suck, Dave, on boost or otherwise ;)

Not if the boost is leaking from the the pressurized parts..

--

The Evo forum really is a shadow of its former self. I remember when the internet was for the elite and now they seem to let any spastic on.

IaFG Supercharged Muppet Division

Had a look about the engine tonight with an in section lamp couldn't see any visible splits or leaks. :?

--

Strong Broo Racing

unzippy said...

JL said...

Engines suck, Dave, on boost or otherwise ;)

Not if the boost is leaking from the the pressurized parts..

True but it won't be making boost at idle Dave, unlike your G wagens (see what I did there?). I could be wrong though - it's happened before.

scotta said...

Bit of help guys please.

Ye wife's Got an A4 Avant 1.8T which has started hunting a bit on idle and running a bit rough just on idle. I took it for a drive and it pulls fine right through the rev range. From the bottom of second gear on WOT right round to about 6000 it's smooth, pulls well and you can hear the turbo spool ok.

However On overrun it seems to want to run on a bit. Additionally when the car is stationary revving it to 4000 rpm then releasing the throttle the rev's fall gradually for a couple of seconds before falling as they should back to idle. Idle then hunts between about 700 rpm to 1200 rpm and the engine is a bit rough....

Initially I thought Coil pack but they were all done about a year ago under warrenty and its not running on3 cylinders as it has done in the past when the coil packs went.

I'm gonna get it on vcds later tonight to check for any fault codes.

Any ideas?

Hi

I have diagnosed the problems. It turns out its due to you only having 4 Cylinders installed I'm afraid their is nothing that can be done about it.

Cheers

Steve

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