Audi A4 1.9 TDI (1999) - power loss...limp mode?

**k3t4n** · 13-05-2010,05:38 PM

Having called Audi parts, they said the boost sensor is the MAP sensor. Does this normally come up under a VAGCOM scan? I havent got any codes coming up...worth changing the MAP sensor? yes it is £49...

**lordpleb** · 13-05-2010,06:31 PM

Does it work then suddenly go from lots of power to none or just have none from the start? I have a 90hp A4 and that had a clogged cat + a leaky boost pipe so the cat wouldn't allow the exhaust to spin the turbo properley and because of the boost leak it meant it was very hard to diagnose. I fitted an aftermarket Frontmount Intercooler and new pipes as soon as i did that it wouldn't idle cos of lack of turbo. This car felt like it was in permenant limp mode from the word go.

**yuley** · 13-05-2010,07:28 PM

If i was you then yes i'd try the map sensor it worked for me, you always have to eliminate the cheaper parts first before you start getting to the more exspensive bits, i replaced the n75 valve and it made no odds but the map sorted it out straight away and i wasn't getting any codes up that pointed straight to the map sensor either only 17965 which is boost pressure deviation which the map sensor is all about measuring the boost pressure. Hope it sorts out your problem, and if your car isn't kicking any nasty smoke out the back end then i would put money on a sensor problem rather than turbo..

**lordpleb** · 13-05-2010,07:35 PM

Originally Posted by yuley

If i was you then yes i'd try the map sensor it worked for me, you always have to eliminate the cheaper parts first before you start getting to the more exspensive bits, i replaced the n75 valve and it made no odds but the map sorted it out straight away and i wasn't getting any codes up that pointed straight to the map sensor either only 17965 which is boost pressure deviation which the map sensor is all about measuring the boost pressure. Hope it sorts out your problem, and if your car isn't kicking any nasty smoke out the back end then i would put money on a sensor problem rather than turbo..

Isnt the Map sensor built into the ECU? But when the cat was changed the car worked fine infact the best it has run.

**yuley** · 13-05-2010,08:57 PM

Originally Posted by lordpleb

Isnt the Map sensor built into the ECU? But when the cat was changed the car worked fine infact the best it has run.

Yes sorry your right, i'm talking about the boost sensor thats sat on top of the main pipe that runs at the rear of the engine, it's held in place with 2 screws.. The part number is 038906061C Sensor £49.48

**lordpleb** · 13-05-2010,09:02 PM

Originally Posted by yuley

Not sure, i'm talking about the boost sensor thats sat on top of the main pipe that runs at the rear of the engine, it held in place with 2 screws..

I think on the earlier models its built into the ECU.

**trickyfocus** · 17-05-2010,04:41 PM

I'v got a4 1.9 tdi 110 ... I had same problem...... it was a hose split that goes to the turbo. it was split at the back so you could not see it till it came off.... the one with two jubilee clips and it's about 2 inch long and 2 inch thick.... orderd a new one 23 squid from audi. It's like driveing a diffrent car hope this helps.

**k3t4n** · 18-05-2010,01:08 AM

Ok ordered a MAP sensor from Audi...will see how that goes once I pick it up in the next couple of days.

Can someone tell me what the plastic ball type thing located in the left hand side of the engine bay is? its a little way down into the engine bay, and the vac lines run into this and the braid is v frayed. Do I just pull the end off the ball to replace? Or does that require me to remove the ball thing as well? any help here would be most appreciated. thanks

**the_old_diver** · 18-05-2010,10:48 AM

Can someone clarify things for me here; are we talking about the Mass Air Flow meter thing (MAF) just after the air filter or something else and if so what? Bit baffled by the acronyms. Thanks, OD

**k3t4n** · 22-05-2010,01:31 AM

no not the MAF sensor (mass air flow), but the MAP (manifold absolute pressure) sensor which is at the rear of the engine bay.

I have now changed this and paid £49 and annoyed as I still have turbo lag. I feel theres got to be a leak somewhere along the pipe that goes from the vacuum reservoir to the egr. Can someone help me here? How do I remove the frayed/broked braided line from the vacuum reservoir (looks like a plastic black ball), without breaking it. I suspect you can just pull and it will eventually come off, just like the other vacuum lines I've now replaced. But want to know if I need to take out the vacuum reservoir first. any help appreciated, at my wits end