Polo 1.4 - regaining boost after re-pressing gas pedal

Post Reply
kmmepl
Enlisted
Posts: 5
Registered for: 5 years 9 months
Car Model: Polo 9N3 1.4 TDI BMS 59kW

Polo 1.4 - regaining boost after re-pressing gas pedal

Post by kmmepl »

Hello everyone,
I have mystery problem with my polo 9n3 (1.4 TDI PD, 59kW, 2007).

When accelerating hard the car will "chocke", that is:

- rpm won't go above 2500
- heavy black smoke will go from exhaust
- readings from MAF will go down (read via computer)
- engine eventually will make banging noise

Here is the strangest part:

To fix this when driving, I need to release gas pedal and press it again. Then the car will regain it's power and fix itself!

When "fixed" (after releasing the pedal and pressing it again) the car will:
- drive smooth
- drive with 100% power (just like before this problem)

Here is what's been done to fix this problem:

- fault codes read - 0 fault codes
- replaced EGR valve (old was worn) but no effect on the problem
- replaced MAF sensor - no effect
- replaced MAP sensor - no effect
- replaced n75 valve - no effect
- checked brake assist - brakes good
- checked turbocharger actuator via VCD test - work smoothly
- rechecked turbocharger actuator manually via syringe - works smoothly

Additionaly:

- When accelerating gently, the car might not chocke and drive smooth (but not everytime).

I've made dynamic logs of group 003 in VCDS which I've enclosed below:

Image

Can anyone help and suggest what's the next thing to check? Please help.
Last edited by kmmepl on Wed Jun 20, 2018 11:51 am, edited 6 times in total.
'07 Polo 9N3 1.4 TDI BMS 59kW
Ashveer03
Lieutenant
Posts: 1621
Registered for: 7 years 1 month
Car Make: VW
Car Model: Polo 9n 1.9 TDI Sportline
Location: Durban

Re: Polo 1.4 - regaining boost after re-pressing gas pedal

Post by Ashveer03 »

Incorrectly adjusted actuator gives this problem

Sent from my SM-J500F using Tapatalk

When a car tailgates me, i slow down - then floor it and give them a cloud of diesel smoke to choke on :driving:
kmmepl
Enlisted
Posts: 5
Registered for: 5 years 9 months
Car Model: Polo 9N3 1.4 TDI BMS 59kW

Re: Polo 1.4 - regaining boost after re-pressing gas pedal

Post by kmmepl »

Ashveer03 wrote: Tue Jun 19, 2018 11:59 pm Incorrectly adjusted actuator gives this problem

Sent from my SM-J500F using Tapatalk
Thanks for your comment Ashveer03.

My response is:

I've bought this car almost year ago, driven 6k miles and the car worked good. I never touched turbocharger actuator.

Questions:

Can the actuator be broken instead of bad adjustments and he's the main cause? Or is it the turbocharger itself?
'07 Polo 9N3 1.4 TDI BMS 59kW
Ashveer03
Lieutenant
Posts: 1621
Registered for: 7 years 1 month
Car Make: VW
Car Model: Polo 9n 1.9 TDI Sportline
Location: Durban

Re: Polo 1.4 - regaining boost after re-pressing gas pedal

Post by Ashveer03 »

I doubt it can be broken as it works. Are there any dents on the actuator?

I have a 1.4tdi, that car never gave trouble at all until it was in an accident. I really didnt get a chance to "play" with it. Maybe remove the downpipe and check the wastegate flap? Bushing could be damaged causing it to get stuck at times

Sent from my SM-J500F using Tapatalk

When a car tailgates me, i slow down - then floor it and give them a cloud of diesel smoke to choke on :driving:
kmmepl
Enlisted
Posts: 5
Registered for: 5 years 9 months
Car Model: Polo 9N3 1.4 TDI BMS 59kW

Re: Polo 1.4 - regaining boost after re-pressing gas pedal

Post by kmmepl »

I have BMS engine (VNT turbocharger and DPF filter) so I cannot have westgate. So that won't be it i suppose.

I wonder what to check next. Any ideas?
'07 Polo 9N3 1.4 TDI BMS 59kW
Ashveer03
Lieutenant
Posts: 1621
Registered for: 7 years 1 month
Car Make: VW
Car Model: Polo 9n 1.9 TDI Sportline
Location: Durban

Re: Polo 1.4 - regaining boost after re-pressing gas pedal

Post by Ashveer03 »

Oh ok i thought u had an AMF. It could have sticky/binding vanes. To check that, u got to remove the actuator and move the arm to check it moves freely or not.

I had the exact same issue on a sportline but it was the actuator adjustment causing it.

Also check if the actuator holds vacuum, of the vacuum pipe to the actuator is not cut or being smashed

Sent from my SM-J500F using Tapatalk

When a car tailgates me, i slow down - then floor it and give them a cloud of diesel smoke to choke on :driving:
User avatar
panic-mechanic
Panic's Place
Posts: 26715
Registered for: 21 years 7 months
Membership No: 79
Location: Benoni, putfontein.

Re: Polo 1.4 - regaining boost after re-pressing gas pedal

Post by panic-mechanic »

Track the requested boost and actual at that stage instead of the egr cycle and unrelated stuff. That will tell you if the turbo/vnt/controller is causing the issue. Maf going down to me means the boost has disappeared
Stephan van Tonder - Jhb - Putfontein Benoni
'05 Audi A6 3.0L TDI Avant
'09 Touareg 3l TDI
'13 VW CC 2l tdi (repair project)
'05 Touareg v10

Perfect Power dealer. I do dyno tuning.
kmmepl
Enlisted
Posts: 5
Registered for: 5 years 9 months
Car Model: Polo 9N3 1.4 TDI BMS 59kW

Re: Polo 1.4 - regaining boost after re-pressing gas pedal

Post by kmmepl »

panic-mechanic wrote: Wed Jun 20, 2018 12:02 pm Track the requested boost and actual at that stage instead of the egr cycle and unrelated stuff. That will tell you if the turbo/vnt/controller is causing the issue. Maf going down to me means the boost has disappeared
I've tracked requested boost and actual when fault occurs, here is a plot of group 011:

Image

Also if you prefer numbers, here is a link to dynamic log: http://vaglogi.pl/log-011_y2V0817.html (fault occurs from 9s)

Second log: http://vaglogi.pl/log-011_010_003_KFL5NZ.html (with EGR blinded by me - I thought that it was the cause, fault occurs up to 15s)

Can you see what is causing the issue?
'07 Polo 9N3 1.4 TDI BMS 59kW
User avatar
panic-mechanic
Panic's Place
Posts: 26715
Registered for: 21 years 7 months
Membership No: 79
Location: Benoni, putfontein.

Re: Polo 1.4 - regaining boost after re-pressing gas pedal

Post by panic-mechanic »

Yeah so requested is way more than actual. So either stuck vanes in the turbo or the controller is defective or set incorrectly.
In simple terms the turbo is simply not supplying what is requested from it.
Stephan van Tonder - Jhb - Putfontein Benoni
'05 Audi A6 3.0L TDI Avant
'09 Touareg 3l TDI
'13 VW CC 2l tdi (repair project)
'05 Touareg v10

Perfect Power dealer. I do dyno tuning.
kmmepl
Enlisted
Posts: 5
Registered for: 5 years 9 months
Car Model: Polo 9N3 1.4 TDI BMS 59kW

Re: Polo 1.4 - regaining boost after re-pressing gas pedal

Post by kmmepl »

Ok thank you for your suggestions.

Tomorrow I will disassemble the turbocharger and check its vanes and check turbocharger actuator.

panic-mechanic wrote: Thu Jun 21, 2018 6:49 am Yeah so requested is way more than actual. So either stuck vanes in the turbo or the controller is defective or set incorrectly.
In simple terms the turbo is simply not supplying what is requested from it.
Is there any way to diagnose defective controller? Is is common that controller in a car will be bad?

--------------------------------------------------------------------------------------------------------------------------------------------------------

UPDATE: car is "fixed"!

I've "calibrated" turbo actuator rod (made 3 and half turns with spanner on the calibrating nut). And now it drives better than at the beginning when I bought it. No smoke, smooth RPM.

I didn't managed to dissasemble the turbo because of lack of clearance (couldn't use any of my tools, too much elements in one place).

But here is the strange part:

For well over 6000 miles, nobody touched turbo actuator, car was driving fine (it was a bit less smooth compared to now). Nothing was happening until this fault occured.

So the question is:

Why after driving it for almost a year, I needed to "calibrate" the actuator? Does anyone know?
'07 Polo 9N3 1.4 TDI BMS 59kW
Ashveer03
Lieutenant
Posts: 1621
Registered for: 7 years 1 month
Car Make: VW
Car Model: Polo 9n 1.9 TDI Sportline
Location: Durban

Re: Polo 1.4 - regaining boost after re-pressing gas pedal

Post by Ashveer03 »

The nut probably loosened itself by vibration? Was it tight when u adjusted?

Sometimes things can't be explained, funny stuff happens to cars at times..

Sent from my SM-J500F using Tapatalk

When a car tailgates me, i slow down - then floor it and give them a cloud of diesel smoke to choke on :driving:
Post Reply