Boost Issues. Help please

[MSTRKRFTSMN]

Last week I changed the breather hoses on my 2002 s3 BAM for the 034 Motorsport silicone kit and put in an OEM air box and new filter to replace an old broken cone filter from a previous owner. I had been having boost issues which worsened to the point I could hear the dump valve working but had zero boost. Anyway, this sorted the problem and my car was back to normal.

Annoyingly, this lasted a week. On my way home from work I had no boost again. I assumed it was a loose hose and decided to sort it in the morning.

When I went to inspect I found all my breather hoses were fine but there was a tiny bit of white smoke coming from the back of the engine. I later noticed a similar bit of smoke coming from the exhaust. I went for a short drive and the smoking stopped completely. Still no boost of course but I noticed I cannot even hear the dump valve any more. I've also noticed when I unplug my MAF the car runs slightly better, albeit still with no boost so I assume that's also ********.

So: breather hoses ok, minor smoke (now gone) MAF iffy, no dump valve noise, no boost.

Any pointers would be appreciated.

Could the new breather hoses etc have screwed my turbo up somehow?

 

[<tuffty/>]

Have you scanned for fault codes? don't assume anything until you have at least done that...

<tuffty/>

 

[MSTRKRFTSMN]

Cheers for the response. I got it scanned locally in Didsbury manchester before I sorted the breather hoses and am reluctant to spend another £60 on diagnostics. Is there anybody in Manchester who could help me out cheaper? I just need a quick scan

 

[A3QuattroAdam]

Buy a cable off eBay and get the free version of vag-com from the Ross tech website. Be a lot cheaper and you'll end up using it again

 

[MSTRKRFTSMN]

Ok I ordered a cable, due wed. Will let you know his it goes.

Also found a local guy through the VCDS map on here who'll scan it for £20. But let's see what the cable does for be first.

Cheers for the help so far

 

[Samuealle]

If you have intermittent boost I would be checking the line from the actuator to the n75 valve. Its an easy hose to twist and would provide the issues you have currently.

 

[MSTRKRFTSMN]

OK, i just scanned my car using the cable off ebay:

Version:0.9 StartHtml: 105 EndHtml: 4183 StartFragment: 334 EndFragment: 4151
3 Faults Found:
16486 - Mass Air Flow Sensor (G70): Signal too Low P0102 - 35-10 - - - Intermittent
17963 - Shareware Version. To Decode all DTCs P1555 - 35-00 - Please Register/Activate
17956 - Shareware Version. To Decode all DTCs P1548 - 35-10 - Please Register/Activate -
Intermittent Readiness: 0000 0000

I also had a play around with the software and...:

*my car is idling at 720-760
*lambda reading varying between -3.9% and 4.9% at idle

Any ideas?

 

[MSTRKRFTSMN]

OK I did a bit of reading and its looking like an N75 issue, which isn't being helped by an iffy MAF.

i'm new to this and just read that guy cleared the code and it went away temporarily. I'll try that and report back

 

[MSTRKRFTSMN]

Cleared the codes and hey presto. My boost is back! Is this likely to be a recurring thing until I replace something?

 

[<tuffty/>]

Considering one of your codes was an over boost code I suspect it will go into limp mode again if there is still a problem

<tuffty/>

 

[MSTRKRFTSMN]

Assuming it goes into limp mode again. What would be your advice?

looking at the time line:

Intermittent boost
No boost
Scanned by local garage threw up 3 fault codes
Changed breather hoses, new OEM airbox and filter
Worked for a week
Scanned with eBay cable shows same 3 fault codes
Clear codes and it works


im starting to wonder if the garage had just cleared the codes, would it have sorted this issue as I have just now? If yes, then maybe the hoses weren't to blame after all (they were old - in one case warped/collapsed - and in need of replacing but no noticeable splits), and so I would then be inclined to think it could be the n75 needs replacing.

If the problem reoccurs but the MAF code is gone and I've just got the two over boost faults ( I hadn't cleared the code after changing the old broken cone filter for the air box), would this narrow it down to the n75?

 

[Stuson]

Just read all of the above.
Minor note, when using the stock airbox the dv noise will not be very noticeable. Also if your car was custom mapped with a cone filter it wont really like the more restrictive flow of the airbox.

If the MAF code keeps coming back that means it's knackered, this also messes up the engines running and will reduce power the worse it gets.

N75's do fail and I believe that could lead to too much boost or not much boost.

If you haven't already checked the hoses that go underneath the inlet manifold, that may be worth doing too.

Also check the dv isn't split assuming it is still the oem Bosch unit.

 

[MSTRKRFTSMN]

Update. Boost issue came back today. Scanned it again and only the over boost code came up. No MAF related code and the car feels notably less lumpy even in limp mode compared to before I did the first code reset.

Same happened again later on and same results.

It seems when I hit 4000rpm the limp mode kicks in.

Does this narrow the investigation at all? I haven't had chance to get under to bonnet just yet but Ihsvr inspected it quits thoroughly in the last few weeks there aren't any split pipes/cracked valves that I could see.