Hi guys,

 

 I posted a while ago when I was having a problem with my '02 1.9 TDi Fabia's turbo dropping out between about 2000 and 3000 RPM in 5th gear or when accelerating up a particularly steep hill and the like. I originally replaced the MAF sensor with a cheap compatible part, this didn't fix the problem so I tried the Mr Muscle technique which worked for a few weeks before the same again.

 

Eventually I opted to change the turbo, however being a poor student I bought a used one from the forums here and got the Uni mechanics to fit it. It's not as frequent now, but I still have it drop out with high revs in 5th gear occasionally. It's not unbearable and simply turning the engine off and on again while rolling resets it but it is an annoyance. I was just wondering if anyone could suggest anything I might have missed, should I try to replace the MAF again with a Bosch branded one? Is it more likely that the used turbo I bought also had carbon build up and I'm experiencing more sticky vanes?

 

Any input would be appreciated. Cheers!

Have you change the map sensor or check the wires to the map sansor

I have not, at the risk of sounding daft, where would I find  that sensor in order to check it?

You should check the N75 assembly, it's far more likely to malfunction than the turbo itself.

Checked the vacuum solenoid block where I think the N75 is housed on my Fabia, all the hoses seem clear. The unit itself is sealed so I can't check inidividual components within.. £200 for a new one though so hoping it isn't this. Used a cheap OBD II Bluetooth adapter and the Torque app on my phone, no faults listed.

 

Not sure if it's the MAP as I got an intake manifold pressure reading of 0.99 Atm which is where I think it should be when standing. Please correct me if I'm wrong.

your MAP is close enough   can you rig a vac line and gauge tapped into the turbo control line to see if anything odd is happening ---assume you've thoroughly checked all the vac pipes  and you have sufficient vac at all times?  p.s always start with the cheap and simple stuff :sun:

Plus one what sepulchrave said, N75, I suffer from a very similar issue. Put some wd40 down the hoses n see what that does

your MAP is close enough   can you rig a vac line and gauge tapped into the turbo control line to see if anything odd is happening ---assume you've thoroughly checked all the vac pipes  and you have sufficient vac at all times?  p.s always start with the cheap and simple stuff :sun:

I've consulted dad who is the more mechanically minded of the two of us (I hold the torch), and apparently we do have that stuff so will get it checked properly tomorrow. I seriously hope it's the cheap and simple stuff! Thanks for the advice

 

Plus one what sepulchrave said, N75, I suffer from a very similar issue. Put some wd40 down the hoses n see what that does

I read earlier (possibly one of your posts) via google about doing this and mentioned it to dad. He seemed to think spraying a fluid into a vacuum line was a bad idea.. Perhaps I just explained what I read wrong. Are there any potential negative side effects to this?

I wouldn't squirt anything down which could thicken and stick up delicate valves   remember some are not on or off but vibrate at high speed varying the proportion of time open to shut   if you have the N75 valve in isolation as opposed to the "multi-block"  it can be temporarily switched with it's twin which one I have forgotten---- but do search on here or on SEAT Cupra Net  (can I say that on here /  )  look for posts from STU

I wouldn't squirt anything down which could thicken and stick up delicate valves   remember some are not on or off but vibrate at high speed varying the proportion of time open to shut   if you have the N75 valve in isolation as opposed to the "multi-block"  it can be temporarily switched with it's twin which one I have forgotten----

 

Thanks for the advice, will try and get lines vac tested today.

 

but do search on here or on SEAT Cupra Net  (can I say that on here /  )  look for posts from STU

 

I won't tell if you won't!

Not had a chance to guage the lines but took it out aiming to replicate the problem with a bluetooth OBD II and Torque on my phone. Took screenshots of normal driving and after the turbo dropped to see if it makes sense to anyone here:

 

Cruising at 70Mph no problems at all:

 

 

 

Lost turbo, if I recall correctly doing 60Mph with foot hard down:

 

 

Does this mean anything to anyone? I believe I had a MAF sensor, an air intake pressure sensor and the turbo PSI up.

Edited 18 September, 201411 yr by shogran

Those numbers are really unhelpful, you have three out of four gauges that relay exactly the same information (the MAP reading) in three totally different and largely useless ways.

 

The MAF reading is in g/s, what the hell is g/s, gallons per second? This isn't 'murrica, we use metric measurements and so does your european cars ECU.

 

1.8 bar suggests that maybe the ECU is sensing overboost and shutting the turbo down. Otherwise, nothing, sorry.

" Is it more likely that the used turbo I bought also had carbon build up and I'm experiencing more sticky vanes?"

 

I'd put money on it.

 

Thanks for the help and advice guys. Got another vacuum block on order on the chance that fixes it.. I think it's safe to say it's just another sticky VNT. I'll have to put up with it or sell the car to someone who has the time/cash to fix it as I have neither at the moment unfortunately!

Those numbers are really unhelpful, you have three out of four gauges that relay exactly the same information (the MAP reading) in three totally different and largely useless ways.

 

The MAF reading is in g/s, what the hell is g/s, gallons per second? This isn't 'murrica, we use metric measurements and so does your european cars ECU.

 

1.8 bar suggests that maybe the ECU is sensing overboost and shutting the turbo down. Otherwise, nothing, sorry.

 

Grams per second.  Metric as anything.

Grams per second.  Metric as anything.

 

Thanks Wino, I was scratching my head trying to think of a volumetric measurement when it was mass all along, silly me.

 

OP: Aren't you tempted to have a go with some Mr Muscle?  Dunno what access is like on a Fabia, but on a mate's Octavia (110) we had a go at, it was easyish to disconnect the exhaust from the hot side of the turbo, and spray the stuff straight in there, rather than the gamble of poking a tube down from above and not being too sure where it's gone.

 

OP: Aren't you tempted to have a go with some Mr Muscle?  Dunno what access is like on a Fabia, but on a mate's Octavia (110) we had a go at, it was easyish to disconnect the exhaust from the hot side of the turbo, and spray the stuff straight in there, rather than the gamble of poking a tube down from above and not being too sure where it's gone.

 

Tried that on the last one, did it the hard way too! It's worth a punt on this one, just got to find the time to get it all apart. I did get some innotec turbo cleaner stuff that's still lying around as I never got around to getting underneath and taking the exhaust end off.. Worth trying that or just Mr Muscle?

 

Thanks