Power loss issues on FR TDI 55 plate!!

[Foz550]

Hi everyone, I am after a bit of advice!

Am having big issues with my leon FR TDI, it keeps intermittently losing power (feels like the turbo goes) which if I turn the engine on and off again stops the problem and all is well again.

VAG said it was the fuel pump relay, so had that changed & still same issue & I have now had the fuel pump changed as well and I still seem to be losing power intermittently.

When I had the fuel pump changed my mechanic did a lot of VAG tests etc & it came up with the following code/problem:

17957 - Boost Pressure Regulation Valve (N75): Open or Short to Ground

P1549 - 35-10 - - - Intermittent

Anyone got any ideas on what my problem could be? Is it likely to be this N75 valve?

Ive also had the following code come up a few times, do you guys think I need to change the fan system?

18080 - Coolant Fan Control 1: Open or Short to Ground

P1672 - 35-10 - - - Intermittent

Thanks in advance!?
Dave

 

[delaxm]

I had a similar problem, got a lot worse after the car had been bogged down in slow moving traffic.
Fault code P1556 charge pressure negative deviation was logged by VAGCOM - I checked for boost leaks but found nothing then added some fuel additive & gave it a good thrash - problem went away for about 5 weeks!
It does it now & again but so few & far between that I've not had another look at it.

 

[MATT'88]

Could it be the dpf?? But without the dpf light showing???

 

[delaxm]

Did they fit DPF to a 55 plate?

 

[volvic]

55 plate was the change over(mines a 55 mk1)... going by the OP's username he has a mark 2 (with dfp)

 

[Foz550]

Mine is a mark 1. Prob gonna sound stupid here but what is the dpf?

 

[CrispDust]

particulate filter on exhaust.
Have you checked all boost pipes (are you getting any white smoke out of exhaust?)
MAF knackered?
What milage is it?
It could be the VNT on your turbo - seizies up with carbon/crap causing overboost and limp home mode. Can be repaired by turbo removal and clean up internally

 

[sssstew]

Mine is a mark 1. Prob gonna sound stupid here but what is the dpf?

there isnt one if you have a mark 1.

 

[Foz550]

no smoke coming out of exhaust at all - generally I don't even notice it when it goes into limp mode until i put my foot on the accelerator. its done 54,000k. Had remap at around 15-20k approx 2 years ago.

 

[BigDave34]

If it was an old Tdi I'd say definately MAF. I've had a few of these go and they don't always do the same thing? a Passat i owned would re-set if you turned the ignition on and off but then would drop into limp mode when overtaking anything!!. The Ibiza i've just sold was just low on power all the time and it turned out to be the MAF again.

 

[_Mike_]

My car has just developed this exact fault, if your on boost for more than a few seconds, it goes into limp mode until restarted, What was the outcome of this?

 

[brad1]

Try a new maf mate

 

[n11tht]

did you get this problem sorted? ive got the same code and same problem

 

[Viking]

If you say you've got the same problem and the same code, do you mean the original poster and his code, or the second guy who posted a different issue?

If it's the first one [17957 - P1549 - Boost Pressure Regulation Valve (N75): Open or Short to Ground] then there's a clue in that very statement. Boost Pressure Regulation Valve (or N75 as it's more commonly known) most likely faulty. However, if you've just seen the same symptoms and thought it sounded like yours then you need to get the fault code read to point us in the right direction.

Edit: another issue which might throw up the same error code would be the wiring to the N75 valve being faulty.

 

[mamdc]

Hi all, I'm having the same issue and it's doing my head in. The codes picked up so far have been the N75 valve short to ground and the fuel pump relay - in addition to the coolant fan 1. Had the N75 valve replaced and the fuel relay changed too but the problem remains. The car is at my local SEAT specialist and they're being less than helpful at the moment. Last time it went in they said it's likely that the fuel pump will need to be changed if the problem continues but by the sounds of Foz550, this won't fix it. Any more thoughts...?

 

[Mike FR+]

Sounds like the variable veins sticking in the turbo. I have just had to sort out a turbo recon to sort mine out.

When it goes into limp mode its because the veins stick. Turning off the engine allows the variable veins to reset, and cause no problem until the ECU causes and overboost when they stick again and you go into limp mode again.

 

[glynnd]

But that would give a different code, relating to positive or negative deviation in boost, not an
N75 related problem. I think its a communication error to the ecu, this problem particularly applies to mapped cars. Mine does it every now and again and I dont believe there is anything that can be done about it other than to revert back to the original map.
Glynn

 

[vdubzfr]

Hi everyone I'm I knw it's them same thing I'm posting wars already been written but I've got same prob. Initially I had boost pipe leeks so I replaced both inter cooler pipes the metal crimped one on driver side and rubber one on pass side but the problem came back after two days the car goes in to limp mode alot and it's not showing any fault codes any help lads thanks

 

[MJ]

Search For limp mode or have the turbo stripped and cleaned.

 

[mark29]

losing power

Hi i have a problem with my leon fr ,i have lost alot of power in my car for some reason .i got it checked out and there are no pipes loose but pressure boost sensor is faulty but would that cause me to lose alot of power ?can anyone help