AMK Boost issues

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Dicky A

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Ladies and gents,

I'm looking for some advice on a boost issue and this seems a good place to ask!

I've got a 2003 AMK engined S3 with a lovely stage 2 map and in 18 months ownership it's been an awesome machine. Just recently the car has developed a boost problem and I'm not sure where to start in diagnosing it - I'm familiar with Land Rover turbos but S3s seem to be a little more technical!

Basically, the car runs perfectly trundling round at low revs but as soon as you put it under load and get the turbo spinning, then the engine becomes really lumpy, hesitant and gutless. It seems to be burning a lot more fuel that normal so I'd guess it's dumping fuel into the cylinders whilst this is all going on.

Also, normally the turbo gives a nice deep whooosh noise but now when boosting it literally sounds like someone has turned the air conditioning fans on high, with a fan noise coming from behind the dash - it's really weird! When revving the car at standstill I can hear the turbo whistling, so I'm pretty sure it's spooling up alright.

Anyone got any ideas?

I'm thinking a big *** boost leak somewhere but have no idea how to diagnose. Incidentally the brake pedal is also really soft, don't know if this might be related?

Any help/guidance much appreciated!

Peace out.

Dicky A
 
Sounds like a leak mate, you checked all boost pipes? With where your saying the sound is id check the elbow that comes of the turbo onto the charge pipe! Also get it scanned for fault codes.
 
Cool, thanks for the advice. Glad it sounds like a boost leak and not a ****** turbo.

I've had a quick look at the hoses I can get to but can't see anything obvious. Doesn't help that I've got hands like shovels, it's a bit tight down the back of the bay!

What's the best way to get that elbow out to take a look at it? Does the charge pipe need to come out?
 
If its using fuel like you say and sounding a bit misfirey under boost it could be the EGT probe thats malfunctioned... as mentioned you need to scan for fault codes in the first instance and post up the results...

Info on how to do this and the kit you need plus links to sites to understand the codes etc is linked in my signature below... I would be doing this before taking the car apart at this stage...

<tuffty/>
 
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Thanks for the suggestions all. Badger5, if I were closer I'd run it down to you to take a look but I'm over 100 miles away.

When on boost it doesn't misfire as such, it's hard to explain - it's just very lumpy and hesitant and doesn't boost at all. The turbo also sounds very different to normal, like it's not achieving any pressure. It literally sounds like someone has switched the aircon up to high, very odd.

I haven't got the kit to read the fault codes so will have to get it booked in somewhere locally I think. It's not my daily driver so I'm not overly worried but do want to get it sorted. Anyone know of any decent VAG specialists in the Berks/Bucks/Surrey areas?

Otherwise is the VAGCOM kit readily available? Could I 'acquire' a copy and buy the connector on ebay?
 
Dicky A said:
Thanks for the suggestions all. Badger5, if I were closer I'd run it down to you to take a look but I'm over 100 miles away.

When on boost it doesn't misfire as such, it's hard to explain - it's just very lumpy and hesitant and doesn't boost at all. The turbo also sounds very different to normal, like it's not achieving any pressure. It literally sounds like someone has switched the aircon up to high, very odd.

I haven't got the kit to read the fault codes so will have to get it booked in somewhere locally I think. It's not my daily driver so I'm not overly worried but do want to get it sorted. Anyone know of any decent VAG specialists in the Berks/Bucks/Surrey areas?

Otherwise is the VAGCOM kit readily available? Could I 'acquire' a copy and buy the connector on ebay?
Click to expand...

Check the link in my signature dude (not my build thread although please feel free to read that too lol)... its the same link as the one in the stickies at the top of the 8L section :)

<tuffty/>
 
Haha! I clicked on the build thread after your earlier post and was like, wtf?! Clicked the other one and got the info on vagcom now, cheers!

Downloaded and cable ordered - time to see what-a-da-hell-is-a-goin-on-a!

Thanks for the advice, I'll post back as soon as I can read the fault codes!
 
Right, whilst waiting for my diagnostics cable I thought I'd have another scoot around the engine bay - managed to get my hand down to the turbo and confirmed the main clamps and hoses are all tight. I then turned my attention to the Forge DV - removed it and checked it wasn't stuck, which it wasn't.

Then I found the below hose where the OEM clip has gone loose - could this perhaps explain my boost issue?

s3hoses.jpg


With my limited turbo knowledge (!) I *believe* that these hoses are vacuum hoses and are related to control of the DV - my theory is that if these hoses do not hold vacuum the DV will stay in the wide open position and dump boost all the time, which would certainly be consistent with the fan noise from behind the dash.

I'll obviously replace the clip asap, but in the meantime can anyone confirm that this is a viable theory???

Cheers all.


Dicky A
 
What you have hold of in that picture is a hose to the N249 valve and the vac reseviour that does indeed control the DV when the ESP system wants to intervene. Anyway, best bet is to do a N249 bypass as described in a thread in the stickies section. Most of the OEM pipes tend to split and perish so it's best to replace as much of the rubber hose with silicone.
 
Dicky A said:
Thanks for the suggestions all. Badger5, if I were closer I'd run it down to you to take a look but I'm over 100 miles away.

When on boost it doesn't misfire as such, it's hard to explain - it's just very lumpy and hesitant and doesn't boost at all. The turbo also sounds very different to normal, like it's not achieving any pressure. It literally sounds like someone has switched the aircon up to high, very odd.

I haven't got the kit to read the fault codes so will have to get it booked in somewhere locally I think. It's not my daily driver so I'm not overly worried but do want to get it sorted. Anyone know of any decent VAG specialists in the Berks/Bucks/Surrey areas?

Otherwise is the VAGCOM kit readily available? Could I 'acquire' a copy and buy the connector on ebay?
Click to expand...

beachbuggy is in surrey..
sounds more leak related to me... look for oil y pipes under your inlet manifold.. if they're oily there a split allowing boost to blow out oil breather oil... Its vacuum leak as well as boost leak and would explain what you describe.. Very common.

See here> Timeline Photos | Facebook
 
Right,

Sorry for delayed response. I've had a look under the bonnet for oily hoses and couldn't see anything obvious. The previous owner had a collection of OEM hoses replaced with Forge Motorsport items, including most of those under the inlet manifold.

Since my last post I've now got my cable and a copy of VCDS Lite - I slapped a tax disc on the screen this morning, took her for a drive and came home to scan for codes.

The only code that came back was P1602 which relates to "Power Supply B+ Terminal 30: Voltage too Low". The car has been standing for 3-4 months so the battery isn't in great shape which I think will explain this.

I guess the next stage is to perform some data logging runs. I checked Tufty's FAQ and it doesn't detail how to do this - can anyone help? I had a scoot around the VCDS software and found where I can scan blocks but I'm out of my depth to be honest, this is the first time I've used VCDS and I don't really know what I'm doing...


Cheers

Rich
 
Sorry to bump an old thread. I finally got some proper car time today and have traced the issue back to a failed hose on the hot side of the turbo - the elbow that sits between the turbo and metal charge pipe. The lip on the turbo join has been blown to buggery so it slips past the jubilee clip under pressure, which is ever so slightly annoying.

My local Audi stealer wants £130.00 for this piece (they can get f****d!) so I've been looking at a Forge repacement, anyone know the best place to get hold of one other than flea bay?
 
So it seems. I didn't realise Forge sell direct so I've ordered a replacement from their website - more Forge goodies!

Cheers for all the help.
 
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