Turbo or sensor issues?

[mephisto]

Picked up new 225 this week. Ran a quick diagnostic picked up some error codes about exhaust gas and disabled ecu will report detail later.
Initial problem though is flatspots. If you give full throttle it's like the turbo won't spool up. Half throttle and it spins up and pulls hard. It's like it's overboosting? When turbo does spin up bit of a rattle may need investigating here also. Any pointers appreciated. TIA

 

[<tuffty/>]

If the EGT sensor is not working it will overfuel (0.75 lambda) running very very rich as thats the default strategy...

Posting fault codes would help with diagnosis though

<tuffty/>

 

[mephisto]

Thanks bud will post them soon as I get home tonight.

 

[mephisto]

Ok one of the codes was definately
Fault Code P1555

 

[<tuffty/>]

http://wiki.ross-tech.com/wiki/index.php/17963/P1555/005461
17963/P1555 - Boost Pressure Control: Upper Limit Exceeded

Not one I have seen often on a 1.8t... could be a problem with the pipework on the N75 so check for splits etc there... pipe from charge pipe to n75 an pipe from n75 to wastegate

Could also be a faulty wastegate

<tuffty/>

 

[mephisto]

Ok I reset error codes and took it for a run which got rid of these..

Trouble codes:
P1455 - Exhaust Gas Temperature Sensor 1 Implausible signal
Intermittent
P1555 - Value above maximum charge pressure
Intermittent
P1456 - Exhaust Gas Temperature Control Bank 1 Control limit reached
Intermittent
P1570 - Engine Control Module (ECM) disabled
Intermittent

After a 15minute run up the road checked again and this was back..

P1555 - Value above maximum charge pressure
Intermittent

Now I took a look under the bonnet and it's clearly been tinkered with. New hoses and clips everywhere and What looks like a valve delete not sure I like how it's just been disconnected and left on the engine I missed this.
See top right on image of engine bay and I unplugged took another pic of it.
Anyway all hoses look replaced and good condition.

Anyway it continues to behave same as op described on this thread actually.

https://www.audi-sport.net/xf/threads/fault-code-p1555.73509/

 

[Tj 0785]

I’m sure that was left there plugged it so it doesn’t bring up fault codes seen it a few times on here

 

[hydro s3]

The 1st picture is of ur catch can and the 2nd one is of the n75 valve. Ur car has had the n249 delete which removes a lot of pipe work from on top of the rocker cover and reduse the risk.of spilt hoses.
Leave that valve in the 2nd picture connected or you will have fault codes for it. Not sure if disconnecting it will do any other issues. If is bothering you having it on view just lengthen the wire and tuck it away some where.

 

[mephisto]

Ok i see N249 delete. And i read N249 delete whilst cosmetically nicer looking it's not actually beneficial to a smoother delivery.

Ok thanks for detail although reading a faulty N75 causes this P1555 error and the symptoms flat spots etc i have? But isn't the N75 here to stop overboost etc, do i have a manual electronic/manual boostcontroller i wonder?

 

[Stuart B]

You need to electronically reconnect the n249 valve or it will get a fault code raised.

Seen people with faulty n75 valves on the ttforums they are only a few quid so i would pick one up if I were you. It's likely been mapped too so you might hee loosing power by intervention, I have this issue if I try and advance the timing on mine.

 

[<tuffty/>]

Trouble codes:
P1455 - Exhaust Gas Temperature Sensor 1 Implausible signal
Intermittent

EGT sensor is goosed... needs replacing...

P1555 - Value above maximum charge pressure
Intermittent

Typically split pipes in boost control 'circuit' (N75), faulty wastegate actuator or possibly a bad remap... could also be someone fitting a hybrid and not having the engine mapped to suit... could be a chinese K04 with its typical tiny wastegate hole or sticking wastegate arm...

P1456 - Exhaust Gas Temperature Control Bank 1 Control limit reached
Intermittent

Faulty EGT sensor can read too high causing this... could also be a genuine restriction in the exhaust blocking exhaust gasses and raising the exhaust temps...

P1570 - Engine Control Module (ECM) disabled
Intermittent

http://wiki.ross-tech.com/wiki/index.php/17978/P1570/005488

Immobilizer issue...scan instruments to see if the immo pickup ring is generating a fault

After a 15minute run up the road checked again and this was back..

P1555 - Value above maximum charge pressure
Intermittent

See previous answer..

<tuffty/>

 

[mephisto]

You need to electronically reconnect the n249 valve or it will get a fault code raised.

Seen people with faulty n75 valves on the ttforums they are only a few quid so i would pick one up if I were you. It's likely been mapped too so you might hee loosing power by intervention, I have this issue if I try and advance the timing on mine.

N75 looks like its been properly removed after all the rework of the new pipes. There's no place for it to go hence it was sitting up in the engine bay.

 

[<tuffty/>]

N75 looks like its been properly removed after all the rework of the new pipes. There's no place for it to go hence it was sitting up in the engine bay.

the N75 or the N249?... as long as the N249 is electrically connected it will be fine... just secure it away from the turbo side of the engine

<tuffty/>

 

[mephisto]

the N75 or the N249?... as long as the N249 is electrically connected it will be fine... just secure it away from the turbo side of the engine

<tuffty/>

Doh sorry yes pic above is N249 indeed it's just hanging about in engine bay ok will do thanks Tufty and thanks for your advice above will troubleshoot this p1555 later. Anyone got a schematic diagram of how boost circuit connects so i can troubleshoot here.

 

[mephisto]

Found this for reference

https://manuals.co/workshop/audi/tt/audi-tt-2000-workshop-manual-self-study-program/2148028/30

 

[mephisto]

Ok removed n75 solenoid checked across contacts 28ohms ok.
Removed solenoid blew through short downward facing pipe which allowed air to waste gate pipe only.
Actuated solenoid with 12v feed allowed air to airbox feed and two short pipes also. All hoses inspection were tight and no cracks. So im moving to waste gate actuator.



So I'm guessing it's one of the second two.

 

[mephisto]

Just posting an update checked all hoses around N75 circuit attached my compressor with 20psi to Wastegate actuator which looked like it was working fine also. Nicked the MAF unit from my beautiful old Santorini Blue S3 (sorry old girl) and bolted that on. Going to spin it up the road and try some logging and or see if its any better. The problem being i went the Odbeleven route and the support seems pretty cryptic on what codes i used to log.
More i read could be that EGT sensor as the code P1455 - Exhaust Gas Temperature Sensor 1 Implausible signal
Intermittent is back also, yes Tufty you mentioned that to start with

Wish me luck!

 

[mephisto]

Just to update on this thread, im still suffering the same issue with P1555 error and boost/turbo spool up at random times. Absolutely zero confidence pulling out anywhere fast as its nearly always a non turbo pullaway when i put foot down.
I've seen a few other threads here with identical symptoms talking about a poor remap or faulty MAP sensor.



Ive now replaced the EGT Pcb from that helpful chap in Poland and EGT is fine. Friend of mine ran a VCDS log for me, where it played up a few times. I have highlighted rpm egt boost and actual boost.

Will attach here. Any comments welcome may go for MAP sensor or this is just a poor remap.