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
Still reckon you will find something like this, perhaps not the seal blown out but the cracking....

intercooler failed seal.jpg


The bottom of the intercooler facing into the engine bay is shown top left, the seal can be seen poking through the splits in the crimped over metal end of the intercooler onto the plastic end cap. You may well have oil in the area partially covering it so give it a wipe with a rag.
 

audifan

A2OC Donor
Post a good picture of the end caps of the intercooler. Remember may also leak from the front face of the intercooler. Although my theory is the lower turbo supply pipe onto the intercooler end cap is not supported by the clip that is bolted onto the sump. These clips never get undone before the engine is lowered to change the cam belt and get broken off. The turbo air pipe then flexes on and off turbo weakening the crimp metal until it splits and dumps the boost pressure.
 

Erlingtheelder

A2OC Donor
Post a good picture of the end caps of the intercooler. Remember may also leak from the front face of the intercooler. Although my theory is the lower turbo supply pipe onto the intercooler end cap is not supported by the clip that is bolted onto the sump. These clips never get undone before the engine is lowered to change the cam belt and get broken off. The turbo air pipe then flexes on and off turbo weakening the crimp metal until it splits and dumps the boost pressure.
This was absolutely the case with mine @audifan It was split down the middle so doing very little. Dad ‘reengineered’ it by forming a bespoke stainless plate the glued an riveted it onto the bracket. Here’s hoping that will help with the life of the intercooler.
 
small update, after hours of getting the egr off i decided to order a new one, im convinced its beyond repair and leaking oil all over the place.
 

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i have physically removed and checked all the pipes today, i have checked to see the actuator moves and it does freely, i have looked over the intercooler best i can and took the best pictures i can but can see no signs of anything leaking :(
 

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audifan

A2OC Donor
The intercooler does look fine, may still have a split that opens up when hot but not obvious. You will now have to very carefully check all the air pipes and joints from the turbo outlet to the "throttle body" for escaping air. You will also have to carefully check the thin braided pipes that run to and from the turbo up to the N75 valve and all joins and connections for ANY damage. The turbo is self regulating using turbo pressure. The N75 valve rapidly provides turbo pressure or vents it to control the turbo "waste gate actuator" if pressure is lost in these lines the turbo waste gate remains in effect open.
 
I have had Every pipe off and checked , I don't have a n75 mine is on the drivers side inner wing in a big block thing , or is that the n75 ? Only place I can see it leaking from turbo to the throttle body would be through the seal on the egr valve
 

audifan

A2OC Donor
It is the fit from pipe to pipe that is important to prevent air leakage. You N75 is in the box on the wing but all the pipes leading to the box need to be checked. how often do you get limp mode and does cycling the ignition "cure" it?
 
It is the fit from pipe to pipe that is important to prevent air leakage. You N75 is in the box on the wing but all the pipes leading to the box need to be checked. how often do you get limp mode and does cycling the ignition "cure" it?
I have checked every one of those pipes one by one , limp mode comes after about 10 mile of driving and no matter how you drive it , I have tried giving it the beans to get it into limp mode but it won't go into limp mode by doing that it doesn't matter if your taking your time neither it's just random , yes turning ignition off and back on will get it going again
 

audifan

A2OC Donor
May be worth replacing the MAP sensor at the top of the intercooler. Still can not see it being an external oil leak on the EGR causing it. 10 minutes things are coming up to temperature and expanding making tiny gaps bigger.
Re the MAP sensor get an OEM one with the numbers printed on the cover as already fitted to your car. Lots of generics have no number printed on the cover.
 

Erlingtheelder

A2OC Donor
I have checked every one of those pipes one by one , limp mode comes after about 10 mile of driving and no matter how you drive it , I have tried giving it the beans to get it into limp mode but it won't go into limp mode by doing that it doesn't matter if your taking your time neither it's just random , yes turning ignition off and back on will get it going again
As per the previous post, I had exactly this issue with my 1.2 TDi a few weeks ago - sorted by changing the Water Coolant Temperature sensor 059 919 501A. This is in the rear of the thermostat housing on the 1.2 TDi ANY engine, above the gearbox and retained by a plastic U clip. Replacements are easy to get off eBay or even Amazon for as little as £4.99 delivered - but get a good make if you want it to last, that includes a new O ring and U clip. This sensor has two functions running from its four pins: feeding the engine's ECU and the dash Water Temperature gauge. The 'tell tale' sign all is not OK with this sensor is if the water temp gauge no longer goes to 90 C when the thermostat opens and stays there, or the needle behaves erratically. I believe there's possibly a logic loop somewhere in the system that compares the two signals and if they don't match may switch the engine control to 'limp' mode. If not, then should the ECU's feed be faulty, but the gauge OK, it's possible all will look OK still on the Temp Gauge. I seem to recall the item concerned is flagged as item G62 when using VAG Com etc.
So, even if your Temp Gauge always goes to 90, even when it's below 0 in U.K., it's worth a check with a new green Water Coolant 4 Pin Sensor - especially if it's as easy to get at as on my engine and you've got the knack of easily removing A2 electrical connectors.....
Good luck! Erling (the real 'elder). #5N007503
 
As per the previous post, I had exactly this issue with my 1.2 TDi a few weeks ago - sorted by changing the Water Coolant Temperature sensor 059 919 501A. This is in the rear of the thermostat housing on the 1.2 TDi ANY engine, above the gearbox and retained by a plastic U clip. Replacements are easy to get off eBay or even Amazon for as little as £4.99 delivered - but get a good make if you want it to last, that includes a new O ring and U clip. This sensor has two functions running from its four pins: feeding the engine's ECU and the dash Water Temperature gauge. The 'tell tale' sign all is not OK with this sensor is if the water temp gauge no longer goes to 90 C when the thermostat opens and stays there, or the needle behaves erratically. I believe there's possibly a logic loop somewhere in the system that compares the two signals and if they don't match may switch the engine control to 'limp' mode. If not, then should the ECU's feed be faulty, but the gauge OK, it's possible all will look OK still on the Temp Gauge. I seem to recall the item concerned is flagged as item G62 when using VAG Com etc.
So, even if your Temp Gauge always goes to 90, even when it's below 0 in U.K., it's worth a check with a new green Water Coolant 4 Pin Sensor - especially if it's as easy to get at as on my engine and you've got the knack of easily removing A2 electrical connectors.....
Good luck! Erling (the real 'elder). #5N007503
That's interesting as mine never goes to 90 , might just fit one in case
 
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