limp mode no power help

hi, after years of trouble free motoring in my little a2 it has now decided to go into limp mode now and then, normally after the car has been running and done a few mile it loses all power.
turning the ignition off and on resets it and it works a little bit then goes again so i presume its in limp mode.
vag com shows code 17964, i have researched and found loads of different solutions, i have checked all the air pipes i can see and seem fine visually, the egr valve looks quite oily, there was a little oil around the pipe that goes into the throttle body and held in with a big clip.
i was reading about the n75 valve but mine doesn't seem to have one on the nearside near the header bottle ?
ive ordered a new fuel filter to start with the cheapest option.
any ideas what it could be or just go through everything i can find on the forums?
 

audifan

A2OC Donor
It only takes a VERY small leak to cause the turbo to go into limp mode. All those little plastic / rubber pipes need to be checked for tightness, splitting and cracks. The contents of the box in the wing need to be similarly checked. The 2 pipes to / from the turbo, the air pipes from the turbo through the intercooler and into the engine for the same tightness, splitting and cracks. The intercooler itself needs a really good check as they are notorious for the end caps splitting due to pressure and the seal blowing out. The pipes may look good but they all need to be thoroughly checked. The last part of the system is the turbo itself......
 

audifan

A2OC Donor
1617211122904.jpeg


Example of the split end cap (lower) with the black seal pushed through.
 
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It only takes a VERY small leak to cause the turbo to go into limp mode. All those little plastic / rubber pipes need to be checked for tightness, splitting and cracks. The contents of the box in the wing need to be similarly checked. The 2 pipes to / from the turbo, the air pipes from the turbo through the intercooler and into the engine for the same tightness, splitting and cracks. The intercooler itself needs a really good check as they are notorious for the end caps splitting due to pressure and the seal blowing out. The pipes may look good but they all need to be thoroughly checked. The last part of the system is the turbo itself......
Thank you , I'm going to try taking the pipes off one by one and checking them thoroughly over the Easter weekend , hopefully it will be one of them , I have my suspicion on the one that fastens to the throttle body it just pushed in and held with a clip , seems a very loose fit and there is some black oil signs around it , would that mean a new pipe ?
 

audifan

A2OC Donor
If you suspect it is the pipe onto the "throttle body" then I would remove it and clean it then find a way to make a temporary very good seal where the pipe attaches, making sure that it can not get sucked into the inlet manifold.. If this then cures the boost loss the well done but I do not think that is the problem. Why not take some nice clear pictures of all the pipes, their joins and the intercooler to see if we can spot something.
 
Ok still no joy on this , thought I would start with the fuel filter as that's never been changed as far as I know , changed that and car now feels much more responsive but sadly still goes into limp mode , next I thought to investigate the pipe into throttle body , it looks very oily so I was going to clean it all up and see if it gets oily again, while there I thought I would take the egr valve off but cannot get to the 2 bottom bolts that hold the pipe to it could anyone shed any light on how you get to them please :)
 

audifan

A2OC Donor
Check the intercooler thoroughly first before considering the EGR. @RAB test with the soapy water and engine running will give obvious results. The usual failure is the lower end cap splitting. Also check the MAP sensor as they have been known to leak and even seen the cap blown off them again with the soapy water. After that you can test all the air pipes after the turbo to the EGR for leaks. That will then confirm the state of all the air pipes. After that I would replace all the little "vacuum" braided pipes ( actually pressure pipes ) to and from the turbo and to and from the N75 valve. If any of the connectors feel mushy or are cracked at all replace them.

Repeat the test on a cold and fully warmed up engine.
 
Check the intercooler thoroughly first before considering the EGR. @RAB test with the soapy water and engine running will give obvious results. The usual failure is the lower end cap splitting. Also check the MAP sensor as they have been known to leak and even seen the cap blown off them again with the soapy water. After that you can test all the air pipes after the turbo to the EGR for leaks. That will then confirm the state of all the air pipes. After that I would replace all the little "vacuum" braided pipes ( actually pressure pipes ) to and from the turbo and to and from the N75 valve. If any of the connectors feel mushy or are cracked at all replace them.

Repeat the test on a cold and fully warmed up engine.
Thank you , checking everything with soapy water was next but since I had the throttle body off I wanted to clean out the egr valve as it's pretty gummed up with grime , I can't run the car now without putting it all back together so thought may as well clean it up
 

audifan

A2OC Donor
Just watch the gunk that comes out the EGR as it sticks to EVERYTHING and is a pain to remove. You will need to fit a new gasket when the EGR goes back on. TBH if you had the old one off I'd just fit a replacement one rather than clean your up.
 
Just watch the gunk that comes out the EGR as it sticks to EVERYTHING and is a pain to remove. You will need to fit a new gasket when the EGR goes back on. TBH if you had the old one off I'd just fit a replacement one rather than clean your up.
Yeah I'm just looking they not expensive , also there is a bypass thing is that worth fitting ?
I just can't seem to find a way to get to the 2 bolts that hold the cooler pipe on :/
 

audifan

A2OC Donor
To get the lower bolts ( a pain ) either way is awkward so here is the 2 ways I have done it in the past. From under the car with a combination of extension bars a universal and a hex bit or from above with Allen keys....
2 schools of thought on the EGR one remove it by machining it and map it our fit a new one. your choice.....
 
To get the lower bolts ( a pain ) either way is awkward so here is the 2 ways I have done it in the past. From under the car with a combination of extension bars a universal and a hex bit or from above with Allen keys....
2 schools of thought on the EGR one remove it by machining it and map it our fit a new one. your choice.....
ive tried for ages today to get them from the top with allen keys but just cannot get one in because of some stupid bar with a hole in it in the way lol, think its for lifting the engine, do you have to map it out if you blank the egr off ? mine is the bhc engine i believe
 
Yes needs to be mapped out. Yes you have a BHC. Other option is removing with the cooler in place. Or not broke don't fix.
how do you remove it with cooler in place? i think something must be wrong with it, there is a lot of oil around that area and looks like its coming out the little hole also in the diaphragm area on it
 

audifan

A2OC Donor
From diagram the cooler is bolted onto the rear of the block or items bolted onto it, a couple of coolant pipes and nuts on the lower flange. I have not removed the cooler myself so may have missed some instructions out.
 
just a thought, you couldn't take it off with the cooler pipe complete because you cannot get to the bolts to remove the egr valve because the cooler pipe is blocking access to them
 

audifan

A2OC Donor
Yep... I would leave it on then and clean what you can. If the Allen keys fail. You have taken off the fresh air inlet from the engine bulkhead?
 
yes ive removed the fresh air duct, the throttle body etc is off just the dirty oily egr valve to come off, even cleaning it in place doesnt give me peace of mind as to why its spurting oil out the little hole though
 
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