audi_marv

Appears autohaus no longer sells this item. Bosch part # is BSH018731.
Try the net, eebay, or europortparts.com. For a photo see thread :

https://www.audiworld.com/forums/sho....php?t=2778278

Nuttynotty

Hi, I have the same issue for a few weeks now, engine code I get is 2121, But the Idle switch is perfect !! I'm pretty sure its fuel pressure, as when stationary I can rev up to 6k no problem ( no engine load), but when the revs fall she stalls ( lack of fuel), turn the key and she fires right back up. when driving cannot go above 3500 RPM no splutter no turbo boost over .8 just will not climb in the RMP, all points to fuel pressure. Pretty sure once you have a fuel pressure gauge installed you will see a lack of fuel pressure. I read that the PSI should be around 100psi ?

Cheers

Jeff-AudiUSAParts

I was looking for a switch that senses manifold pressure but didn't see one listed. But if you have one, and it's defective then maybe the switch is telling the system you are overboosting and it cuts fuel or maybe ignition? I know you said it doesn't feel like it is cutting out. I'd also check that air flow sensor plate and arm to make sure it's not sticking. If it is it will only raise up so far, and that could inhibit air flow and fuel flow both.

audi_marv

Jeff makes a good point about a stuck air plate, or plunger lever. I would also make sure the fuel filter and air filter is on good shape.

Idle Switch/Full Throttle Switch should be checked if code came up.

Another issue could be your Air Temp Sensor, located at the top intercooler opening. Filament inside could be dirty, or broken, and if intermittent, will not throw a trouble code. If this is not functioning, it will limit boost.

Nuttynotty

Hi Guy's

some great feedback, nice to me on a Forum where guys know what they are talking about.

Checked all the sensors last night per Bentley manual, all are within spec, however I did find that my Crank breather hose collapses when you blip the throttle ( flattens as the rubber is very very soft and can’t hold its shape), This breather hose is connected to the turbo, Could this be the rough of the problem ?


My apologies if I’m taking over this thread, it’s all related and I hope it helps all out.

Cheers

audi_marv

Crank breather hose is something you should correct regardless. If you don't have a spare, get a 5"x1" spring from the hardware store and slip it in the hose. This should keep it from totally collapsing. If this fixes your symptoms, then there you go !

Nuttynotty

Yep, hose is on order from 034motorsport.com they have a full replacement item, would do the spring but the rubber is so soft the spring would pop through, runs steep at $135 for the Crank Breather Hose Pair, I also opted for the metal replacement check valve. Be here in a few days, Will update of the results.

Cheers

OMP

Hi.
I finally got he valve kit.
It was difficult as after a research I found that Bosch part 3437010021 is the same as BSH018731. They are usually listed for Mercedes S-class (W126) and some Porsches...It was difficult, but I got the confirmatin hat it is the same part.
I had to browse a bit, thought, to get it, since most of web car parts stores wouldn't make international shipping.

Any how. I should get it in about a week.
As for the other things: Air sensor on top of intercooler is almost new, as all of the rest. However, on the crankcase breather hose, it seems that is OK, but this only has only been changed many years ago. It does feel rigid, thought.

As for the plate or plunger, it could also be a possibility since the car has been sitting for long periods in the last 3-4 years,althought never left apart.....How difficult is to check this? Since is so delicate ( as for what I have read about it), is there a chance that taking it apart and then putting it back together, I may brake or completely mess things up?

Many thaks, and I'll keep reading and bringing news.

Regards

Jeff-AudiUSAParts

If the car has been sitting for 3-4 years, with gas in it and never been running during that time then you could have other issues in the fuel system. Injectors could have a bad spray pattern or partially plugged. Vacuum leaks in the air intake boot, if that is cracked on the bottom side due to age and brittle rubber then you can suck air through there when it needs to be contained around that air flow sensor plate we talked about on an earlier post.

Moisture in the fuel can rust the diaphram in the fuel distributor head too. That usually causes missing at idle and not higher rpm problems though. But you could have the upper part of that port where the plunger goes up and down gummed up. That wouldn't allow the plunger to raise to the level it needs to in order to keep up with the air flow demand needed at 3/4 to full throttle.

Checking the air flow plate for binding is easy. Take off the black rubber air flow boot and first see if that appox 4 inch wide aluminum disc hits the side of the cone that is stationary. Raise the disc all the way up and feel for binding in the lever where it pivots underneath the fuel distributor head. Again, it won't raise all the way if the plunger inside the fuel head is sticky. You can take off those 3 (I think 3) straight slot headed screws out of the fuel head and carefully lift that up from the mount. The plunger is almost a special part machined to close tolerance to fit that fuel head. Don't let it get scratched from falling out but you can remove it easily without fear of something coming apart on you.

Taking the fuel head apart is something I've never done and wouldn't want to. You'll want to research Bosch fuel head diagrams to see what that looks like internally. It will also help you understand a bit how the fuel system works.

Brett Carney

I tried to do a carbon clean using the liquid molly spray with hose attachment yesterday when I went 2 my throttle body the butterfly clip was completely closed I reved the car passed 3500 rpm and still did not open. I have a audi a4 b8 8k 1.8liter 2008 tfsi,was this closed because I had the piping for the throttle body off or do I need a new motor?? The car drives fine but I have a checked check engine light for p201500.when I stay under 20000 rpm I don't get a check engine light but about 3000 rpm my light comes on,if anyone has same problem that they have fixed please let me know. Kind regards