Rough running Mk5 GTI

Started by The Red Warrior, June 04, 2023, 12:06:57 PM

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The Red Warrior

Hi all.
I?ve been having issues with my car running rough for a while.
Bit of background:
It?s a manual running APR Stage 2+. Only engine related mods are a CTS catless down pipe and an Integrated Engineering HPFP upgrade. The car is a bit over 225,000k.
The issues are rough idling on start-up, back-firing from the exhaust under throttle lift off (sometimes half a dozen or so in a row), low boost pressure (sometimes the boost gauge shows just 5 psi at full throttle all the way from 2000 revs to 6000), and generally down on power due to these issues. Sometimes it?s slow to accelerate away from a standstill making pulling out into small gaps in Auckland traffic a bit dodgy. Fuel consumption isn?t great but it?s not dreadful either.
However, other times it drives like there?s nothing wrong at all. Open road driving seems fine except still down a bit on power by the feel of it.

I took it to Giltrap VW in Botany about a year ago for the same issue and they replaced the charcoal canister and N80 valve along with a cracked vacuum line going to the brake booster. The car seemed good after this but only for a few months. I replaced the spark plugs (they looked fine but were due to be replaced anyway) and took it back to Giltraps. They couldn?t find anything wrong and so I got them to do a carbon clean on the intake valves and associated bits. Unfortunately this didn?t solve the issues.
I?ve ordered a new cam follower for the HPFP which I?ll install next week but I doubt that is the issue as I check it at 20k (do oil and filter change each 10k) and replace it at 30k.

Any ideas what it could be or things to check?
I do have VCDS but I?m somewhat of an amateur with it.

Any help much appreciated.


Sounds like either injectors or other issues.

As you?ve had APR on the car almost 8-9 years.
Shoot me a message. I?ll see how I can help
Audi A4 DTM - K04 NZ New | All bolt-ons | Carbon Clean done
2012 MK6R Golf |Stage 3+ | Stage 4 DSG | Tuned & Built by HSP Tuning

The Red Warrior

Cheers Hennie.
I had wondered about injectors and it may have been prudent to replace them when getting the carbon clean done.
Is there a way of checking them with VCDS?
Re messaging you, do you mean a private message through this forum or a text message? I still have your number assuming it?s not changed.

The Red Warrior

So, it would appear that I've fixed the issue.
I replaced the front and rear PCV valves (there was a small oil leak at the back one).
I replaced the rocker cover gasket as that was also leaking (unsurprising as the rubber was basically as hard as plastic).
I replaced the spark plugs, oil filler cap and dip-stick.
None of these fixed the issue.
I replaced the diverter valve with another revision D and all sorted (for now at least). There was nothing visibly wrong with the old one, but it wasn't quite as smooth to move as the new one.

Now I need to find where the rattle is that seems to be coming from the area around the bottom of the windscreen.


Check the wiper mounting bolts.

I had one come loose and it was a bugger to track down the noise.

The Red Warrior

Quote from: schattenblau on March 21, 2024, 03:43:38 PMCheck the wiper mounting bolts.

I had one come loose and it was a bugger to track down the noise.

Cheers. I found out the hard way about that one a few years ago. Alas it's not that.

Also, things have returned to normal: ie crap.
The low intermittent boost problems have returned and I've found oil leaking down the electrical connector from the diverter valve. I've removed the diverter valve and there is oil inside and a small pool of oil inside the cavity in the turbo which it bolts into.

Been doing a little research now and most posts refer to bad PCV valves.
I have replaced front and rear PCV valves recently including gaskets so I doubt these are already a problem.

Was wondering now if my turbo could be leaking oil into the diverter valve.

I'll have a look to see when and which PCV parts I installed and update.

The Red Warrior

Just updating, after cleaning away the oil as best I could from the piston area of the diverter valve and sticking a rag into the cavity in the turbo that it mounts into to remove the small puddle of oil, I put it back together and all seems fine again.
Although there was oil leaking through the electrical connector, it didn't appear to be on the actual metal part of the plug itself and as such I didn't clean that part with any cleaner.

FYI I have also replaced the hoses from the front PCV with braided silicone ones and replaced the seals in the vacuum pump to fix a leak there too.


vacuum leaks you're mentioning would certainly do that too.

Yeah you can shoot me a message on phone as well. Just want to update you to the latest APR software.
Audi A4 DTM - K04 NZ New | All bolt-ons | Carbon Clean done
2012 MK6R Golf |Stage 3+ | Stage 4 DSG | Tuned & Built by HSP Tuning