Can FAULTY n75 cause this

[bigjode]

The car is only bossting to 14psi sometimes, even though I have revo st1 and SPS3, no matter what SPS settings I use. It used to peak at 21, then one day it jsut started acting up.

Also, sometimes, the boost fluctuates and you can see the guage flickering between 14-16 psi as you floor it, especially in high gears.

Actual vs Requested on VAG com is spot on, so does this defiantely rule out a boost leak?

MAF is fairly new, and readt 170g/s (as of yesterday) so i doubt its that.

I'm getting the coolant temp sensor error, but i've had that since i had the car, it just seems to come on more often recently. I've changed the sensor 3 times now and all of them give me the fault code, so i don't know whether I should be concerned about this too much. All I can say is that the car has been fine in the past with this error.

That leaves the N75 to blame then as the most likely culprit. But what are the symptoms of dodgy one? And it can look normal on block 118 and still be broken? (normal being not going over 95% on full load)

 

[Kris]

A leaking exhaust caused my boost fluctuate... ???

I would sugest trying someone elses MAF... ???

What about the Lambda sensors, could they need replacing... ???

 

[richybigman]

As far as i know your maf should be reading in the 190's

 

[bigjode]

As far as i know your maf should be reading in the 190's

Sorry, its just a cupra. Bumper is decieving

 

[bigjode]

A leaking exhaust caused my boost fluctuate... ???

I would sugest trying someone elses MAF... ???

What about the Lambda sensors, could they need replacing... ???

I had the Lambda cleaned recently as it was built up with carbon

 

[richybigman]

My bad
I've got a similar problem but can't find out what's causing it (Boost spike + Fluctuation of boost).

 

[bigjode]

What have you tried so far?

 

[richybigman]

I booked in to a local vag specialist garage who have tried everything but can't find the cause. Looks like it could be a possible ECU fault. They replaced individual parts and tested for about 3 days.

 

[Scotty_b]

I have the fluctuation at 10-15 psi when half on the throttle. Its not the gauge as its a slow surge

 

[richybigman]

Mine spikes to 20psi, drops to 14psi and then slowly increases to 20psi then fluctuates slightly. Used to hold at 22psi.

 

[Big_daddy]

im havin similer problems, revs jam at 5000rpm and boost flickers here and there. the diagnostic said oxygen lambda sensor malfunction, i dont know wat the clue wat dat is! how to fix it

 

[andycupra]

The car is only bossting to 14psi sometimes, even though I have revo st1 and SPS3, no matter what SPS settings I use. It used to peak at 21, then one day it jsut started acting up.

Also, sometimes, the boost fluctuates and you can see the guage flickering between 14-16 psi as you floor it, especially in high gears.

Actual vs Requested on VAG com is spot on, so does this defiantely rule out a boost leak?

MAF is fairly new, and readt 170g/s (as of yesterday) so i doubt its that.

I'm getting the coolant temp sensor error, but i've had that since i had the car, it just seems to come on more often recently. I've changed the sensor 3 times now and all of them give me the fault code, so i don't know whether I should be concerned about this too much. All I can say is that the car has been fine in the past with this error.

That leaves the N75 to blame then as the most likely culprit. But what are the symptoms of dodgy one? And it can look normal on block 118 and still be broken? (normal being not going over 95% on full load)

yes it does sound like there is no leak as requested v actual seem the same.
have you got a forge DV? check the top is not loose and while there check the rings havnt failed.

also, have you performed an ecu reset? - dissconnect the battery for while then reconnect, (get radio code before as you may need this)
it may have adapted, maybe not, but worth getting the basics out the way before you start spending money.
what settings are you running? timing and boost please.

oh and coolant temp sensor, can you confirm this is the temp sensor and not coolant level sensor? (ie one in expansion tank)

finally, where are you? plenty of helpfull chaps and chapesses on here if you wanted to check the N75

 

[bigjode]

Yes, Forge DV, serviced and tested! new rings, piston and special Forge grease used yesterday - no difference.

Also reset adaptation many times on Vag Com.

Using T6 B6 on SPS but have tried various combos of lower T/ higer B and lower B /Higher T.

It still never peaks above 14-16. When the problem first started it was only peaking at 18 and I though that was bad (at the time it was set to B9 T4 for the past 6 months or so and it used to peak around 21)

 

[bigjode]

the collant sensor I have changed is the green thingy that is held in by a plastic clip and has a little rubber 0 ring. The common one.

 

[andycupra]

new or old sps? boost 6 on the old would give you about 14 psi depending on car etc..

 

[bigjode]

i was referring to b6 on the new sps, but I have an old one so its LB9. Saying that though, i've been using HB6 on the old SPS last night to do more tests and still no higher than 16 was reached?

 

[andycupra]

well an N75 swap sounds like it could provide you with the answer, but id want to find a friendly member before splahing the cash! where abouts are you?

 

[bigjode]

Birmingham.

I don't mind too much buying a new one at £35 from VAg parts. But its £57 from dealer. Problem is I can't get one from VAG parts before January i'd imagine.

The thing about swapping them with someone else's is that sometimes the one you swap for isn't too healthy either - luck of the draw i guess?

 

[bentaw]

are you sure your car isnt in limp mode i would try resetting the ecu first

 

[andycupra]

Birmingham.

I don't mind too much buying a new one at £35 from VAg parts. But its £57 from dealer. Problem is I can't get one from VAG parts before January i'd imagine.

The thing about swapping them with someone else's is that sometimes the one you swap for isn't too healthy either - luck of the draw i guess?

well if its on a car thats running well its less likely to be a poorly one. when its new how would you know...