HELP please Mk5 GTI issues

[Ty33848]

Good day to All,

I am new to the forum and have purchased a 2008 Mk5 GTI. 147KW BWA 6 speed Manual

I am currently facing issues that the mechanic can't figure out and it's concerning as he has been working on it for a month already.

My issues are as follows, ( I'm not sure if the vehicle has software but through research it seems like it has a stage 1 software as there are the pops and bangs backfires )

1 The car has a problem revving up
2 The car only boosts after 4000RPM at certain times or doesn't boost at all
3 Intermittent white smoke puffs
4 when driving from jhb to Pretoria I stopped at road block block turned the car off and had to kick start it as it was only swinging on the turn of the key.

The mechanic says it might be the HPFP and has tried others but has not made a difference

The following has been changed,
New Dump Valve
New Boost Pressure Sensor
New Coil Packs
New Oil pressure Sensor
A Full Service Done

It has been about a month,


Please can anyone advise me on how to get the car fixed

[Jet Li]

Greetings, VDCS scan and check what errors comes up. Did you check any possible boost leak?

[Ashveer03]

What problem does it have revving up? Even when stationary?

Regarding boost, after 4000rpm how much boost does it make?

1. could have a faulty n75 valve keeping the waste gate open all the time.
2. Waste gate actuator could be improperly adjusted or faulty. Can be tested with an air line at regulated pressure.
3. Waste gate itself could be damaged, u can tell by removing the downpipe and check the gate.
Easiest way to tell if it's n75 related, bypass the n75 valve and check if it starts to boost as normal.
4. The turbo could be faulty, loose/damaged compressor/turbine wheel. Shouldn't make much boost if this is the case.

Or it could have a problem with the MAF sensor. A dirty/faulty maf can cause alot of kak. Also check for air leaks on the turbo inlet pipe after the MAF.

Regarding the smoke, does it cloud or slight puffs? Could be oil - greyish white smoke. Possibly from the turbo if it's more white than grey.
Does it smoke while idling, when taking off or after a pull?

Regarding not being able to start, it should have logged a fault at that point. This doesn't necessarily mean the hpfp is faulty, it could be low pressure on the low pressure side (from tank to hpfp) - If I'm not mistaken the Mk5 GTi should be 6bar.

This can be monitored from a scan tool Live data or measuring blocks on vcds.

Heck these cars log a fault code for low fuel level. It's quite sensitive, besides low boost wouldn't cause a code because the turbo is only controlled to reduce boost (waste gate opens when the ECU tells it to, otherwise it's normally closed)

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[Ty33848]

When stationary the vehicle struggles to rev up and on the pull away too

When the boost kicks in there is a lot of power and torque


I will have him check points 1 to 3.

At point 4 the car boosts really well when it does kick in

MAF sensor will be looked at, driving with it unplugged gives me high fuel economy and rougher engine noise but then when plugged fuel economy is better with the motor a bit smoother

In Regard to the smoke, when idling there is no smoke but when pulling away there is a cloud of white smoke but this is intermittent

In Regard to the starting the incident occured only this one time, when I left Pretoria a few hours later I had no trouble starting up unfortunately at this time VCDS was not available as I don't own the software but have recently purchased and awaiting delivery, I will await his feedback in regard to testing the HPFP and low pressure.

Hopefully the VCDS should arrive in the next week.

Could any of these issues relate to cam timing perhaps as I have came across a post relating to the same issues I'm facing ?

This is my 1st time owning a GTi and when purchasing the vehicle all was fine and suddenly a month later all these issues occured and quite honestly the previous owner hadn't serviced the car in probably a year so the vehicle was really not well taken care of. At this point it's becoming costly.

Thanking you for your response

[Ashveer03]

Was the PCV checked? A faulty one will usually cause a rough idle and loss of power, sometimes the boost may end up pressurising the crank case. Faulty pcvs are quite a common fault with these engines.
Could eventually lead to some smoking aswell.

Maybe try to monitor how much of oil is needed within 500km.

Timing may cause acceleration issues, it will would definitely throw a fault code if the timing stretches too far. Cam to crank correlation implausible or something like that.

If there's a problem with the fueling system, it could cause all these problems as well, well most of them.
Was the fuel filter replaced with the correct one?

Vcds gonna be your best bet to direct u towards the issue. Without checking what the ECU is seeing, we are just guessing.

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[Ty33848]

The PCV will be changed this week with the N75 valve.

Can't test the oil usage as i am not driving the vehicle at the moment as I do not want to cause any further damage

I will definitely get the timing checked, still waiting for the arrival of my VCDS to run tests

The full service kit was purchased from Gold wagon i would hope that they gave me the correct fuel filter

As soon as the I have the codes I will revert.

You response is appreciated

[Ty33848]

Hi, the VCDS finally arrived and pulled the following codes

000568 - Manifold Pressure / Boost Sensor (G31)
P0238 - 001 - Signal too High

005425 - Camshaft Timing Adjustment
P1531 - 004 - Open Circuit

001681 - Fan 1 Control Circuit
P0691 - 002 - Short to GND

000256 - Mass Air Flow Sensor (G70)
P0100 - 004 - Supply Voltage

000048 - Oxygen (Lambda) Sensor B1 S1: Heatin
P0030 - 004 - Malfunction / Open Circuit


What would be the best way forward ? Auto Electrician or replacement of sensors if so what would it cost for all sensors ?

[Ashveer03]

Look at each of those components and verify if all are plugged in correctly, no physical damage to wiring, plugs or sensors itself.

I would prefer verifying proper wiring, power and grounds before replacing.

Most if not all of those faults are probably sensor faults.

U can clear the codes, and see what comes back, immediately or if it comes back after a test drive. All of those codes except the fan would cause drivability issues.

If I'm not mistaken these fans have built in modules so that means the entire fan has to be replaced. Easiest way to see which one isn't working, turn on the AC.

If buying new spares, pls buy decent brands - preferably from goldwagen.

Use rosstech wiki to help u decode fault codes. Or simply just Google the vcds 6 digit fault code.
http://wiki.ross-tech.com/wiki/index.php/Main_Page

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[Ty33848]

Hi my car is finally up and running with crazy power …

The fix came from a faulty camshaft sprocket that when changed the vehicle boosts really well as it should.

The misfire came from faulty coil packs and a faulty fuel pump


I appreciate all your responses and advice it really helped