Engine cuts off while driving - Golf MK5 GT Sport 2.0 TDI PPD170 BMN engine

[Alcapone636]

This is my first time posting a thread on this forum, so I appreciate your time helping me with the problem in my car.
I will start by saying that my 2007 VW Golf MK5 GT Sport 2.0 TDI PPD170 BMN is very well maintained, with only exceptional workshops working on my vehicle. Between 2017 and 2019, it underwent significant upgrades. I sourced most parts from Darkside Development (intercooler, MAP sensor and many other components) and used brands like Racing Line (air intake), KW (v3 suspension), Vibra-Technics (all relevant engine and gearbox mounts), Milltek, Powerflex (all relevant bushes), Garrett (turbo), and MANN+HUMMEL (oil catch can). Extensive changes and tuning have been done, with almost every old part being replaced with new ones. It also had the whole transmission replaced included the transmission electronics unit. The A/C Compressor is also new.

Most recently, due to this power loss issue, I had the Mass Air Flow sensor kit replaced, the Oxygen sensor, the main ECU replaced with a second-hand unit, the tandem fuel pump, the high-pressure fuel pump, and relays and battery replaced, all without being able to fix the problem.

The annoying part is that the power loss has been an intermittent problem until recently and it still does not show any warning or error code when scanning the ECU, upon the engine cutting off while driving.

The latest attempted repair involved towing the car to the place where it was tuned, in hopes they could diagnose the problem or possibly adjust the tuning file in case it was over-boosting or under-boosting. They ran their own diagnostics andthey could not pick up any over boosting/under boosting symptom. At the time theyassociated the issue with the ECU as after being swapped the unit with the newone I provided them, the car ran normally. It is to note that the firmware on thenew ECU has been cloned from the old one with no changes.


The result was that the car seemed repaired, and I drove back to Sydney from the workshop. For the initial 25 minutes, I experienced no issues whatsoever, even while pushing the car hard. However, the issue reoccurred for the first time after that. Subsequently, the engine kept cutting off, and I wouldn't have been able to make it home (80 km away) until I figured out how to "fool" the system. I timed when the engine cut-off would happen and moved the gear to Neutral beforehand, preventing the ECU from commanding the transmission to change gears and allowing the transmission to decide the gear change instead. I quickly engaged the gear back in again. In this way, I believe I was tricking the system by manipulating the gear to Neutral and then engaging it again to fool the ECU/Transmission.


With the car back home, it eventually got so bad that it just cranked with no starting at all. I attempted replacing the fuel tank relay, with no difference. I did this because this relay (I felt it with my finger) can be hear/felt clicking when power cuts off.
I then replaced the fuel pump and suddenly the car starts with no problems and I was able to drive around carefully, as long as I do that trick with the gear. Nevertheless the cutting off problem is still there.

I don't think it is a transmission issues whatsoever.

I had some opinion from one of my repair shops and they mentioned that based on the description of the issue I gave them, they think that it is likely fuel system related, as the engine cuts off very quickly without the car shutting off. The car does not have rough start or idling whatsoever. They said it might be injectors related (injectors never misfired and mechanic checked with the diagnostics tool they work as expected before).


At this stage my car is not drivable I have it booked to get a new major service done, with timing belt, Water pump, alternator, Crank shaft Sensor, camshaft sensor due to be replaced. Nevertheless I have no idea if this will fix the issue.

I will leave it here, waiting for feedback.

Thank you for reading through. My car hasn't almost moved for the past year and I am starting to wonder what else can I do, to save my joy car.

[Alcapone636]

Here is a photo under the bonnet:




Picture under my car:

[h100vw]

When the fault occurs, does the rev counter drop to zero? That would make me think crank position sensor. Side note, make sure the filter in that racingline housing isnt falling apart. I had one take out 2 MAFs before working out why

[Alcapone636]

Hi, it only drops to zero if the car dies all together when I drive it. Occasionally it does do this, but most of the times drops revs but it recovers and continues driving.

A test that I did was to turn ON the car and leave it still in Neutral for 40mints running, essentially letting the engine temperature build up to its normal 90degC temperature. I then, while still in neutral gently accelerated to around 6,000 revs and the car cuts power.

Yes, the racingline filter was one piece. Nevertheless I got the whole racingline module replaced for the latest version which has a better fitting to the front grill which is a solid box instead of a rubber piece. Most recently I got just the sensor head of the MAF sensor (body pipe still in the car) replaced as well but it did not fix the issue.