Turbo problems

[espanamike]

:mad:Hi guys please please help. This is a long running issue. My turbo goes into limp mode as some of you have experienced. Its the B5 platform 1.9tdi on 97 plate. The turbo has been removed, cleaned carefully by myself as recommended by a mechanic friend, however having had a short period of non limp mode it has begun to go into limp mode more frequently. I have changed the MAF, turbo has been cleaned, so I phoned Audi in Llandudno whom suggested it could well be the N75. An independent reckoned it could be the MAP sensor being faulty and I have read about a potential 3 inch pipe becoming blocked by the ECU, but whether they meant EGR as I read it on a Forum. All in all I think its so simple but nobody seems to be able to pin point the problem. Your help in solving this issue would be highly appreciated. Vacuum pipes is another reason but when the turbo works, it works well and it can work well for long periods. Please help.

[zollaf]

how did you clean the turbo. did you remove the exhaust housing and thoroughly clean the vnt ring... ?

[espanamike]

Hi yes to both the above and used carb cleaner then rinsed both in soapy water. It was sooted up badly and cleaned it up well. Has been fine for a couple of months then the limp mode returned. As I said previously some suggest n75 now another says MAP sensor or Vacuum lines? As previous messages 3000 rpm it goes into limp mode occasionally more so on slight inclines and when engine is cold. Could it be a blockage with oil feeder until it warms up???? So frustrating.

[zollaf]

well, next job is to connect a computer, find the fault code, then go for a drive whilst a passenger observes live data to see what is going on when it hits limp mode. this will eliminate the guesswork involved in replacing bits until the fault is cured. i presume you have an afn engine code.

[espanamike]

yes afn engine

[defever]

Hello espanamike,

Not sure if my experience can help, but here are couple of things you might help pin point your cause without using VCDS (but will have to confirm with VCDS later).

If you think that N75 is the cause (i.e. no vacuum action), you can test this by checking the movement of your actuator. Manually move the rod with your finger (engine off, and you should feel it moving full range), use a hand vacuum pump if you have one. If the rod moves fine, then N75 might be faulty and not creating enough vacuum to move the rod.

Also, check the status of the vacuum hoses. If they are braided OEM black tubes, then they might have pin ***** holes that are hard to see with naked eyes. Check with vacuum pump, if you have any, for any leaks or you can upgrade all the hoses with silicone tube (much better than OEM tubes).

MAF sensor can be easily cleaned, if it's not physically broken. Removing the MAF is very easy and you can get a "MAF cleaner" or simple "electrical contact cleaner" and spray it both ways (make sure it's completely clean before putting it back on).

EGR shouldn't affect limp mode, as it has to do with re-circulating the exhaust gas into the intake.

I hope this helps, and I stand corrected if I mentioned something incorrectly.

Good luck!

[Dangerous Doug]

I had exactly the same problem!
So I attached a hand vacuum to the rubber hose ate the back of the engine bay, at the top of the bulk head.
Holding the small 3mm plastic pipe, I pumped and could feel my finger covering a hole that had worn into the plastic pipe.
So I snipped off the section of the plastic pipe that had worn through from behind and reattached the rubber hose.
Solved the problem! :)