Golf 5 2.0 TFSI - Wastegate rattle and power loss

Hello community,

This is my first post on this forum, and I have to start with a question.

"For the past few months, I've been noticing a rattling noise during deceleration in my Golf GTI (first registered in November 2006, 110,000 km, engine code BWA, no modifications). I've now managed to pinpoint the source of the noise to the turbocharger wastegate actuator. It seems the wastegate is loose and is vibrating/resonating during deceleration."

Furthermore, the vehicle lacks power and does not reach its top speed. I have already replaced the boost valve as a precaution, but the error memory is clear.

Yesterday, I performed a diagnostic run (see attachment). It's clear that the boost pressure builds up very slowly, and the maximum achieved boost pressure seems quite low. In my opinion, the fuel rail pressure/high-pressure pump appears to be working correctly, but it loses all pressure overnight, and the engine starts very poorly.

Nun die Frage: Ist der verzögerte Ladedruckaufbau auf das Wastegate zurückzuführen oder kann es noch was anderes sein? Ich möchte ungern den Lader tauschen lassen, wenn man das Problem auch anders beheben kann...
Is the maximum achieved boost pressure okay (the atmospheric air pressure yesterday was 1005 millibars), or is there something being lost somewhere?

I hope you can help me with this problem, and I'm not sure if this question has been asked before.

Hello,

Unfortunately, the log doesn't really show when and for how long full throttle was applied. It would be better if it logged things like "full throttle in 3rd gear starting at 1500 rpm" and maintained that state as a log entry.

A "sluggish" reaction at 3500 rpm does seem a bit odd, although high outside temperatures like we're experiencing now certainly don't help.

Have you checked if the wastegate lever is simply mechanically "stuck" or "sluggish"? Because it seems to be functioning in principle, since the desired boost pressure can still be regulated.

Best regards, Rainer.

Hello Rainer,

Thank you for the quick response.

I've created another log file that doesn't include rail pressure data, but instead focuses on speed and time.

Is that more helpful? I'm still practicing with logging.

Air pressure at Hanover Airport yesterday was 1003 hPa. Today it is 1002 hPa, and initially continues to decrease. The sensors in the vehicle are not necessarily precision instruments. Currently, the air temperatures (slightly below or slightly above 20 degrees Celsius in the Hannover area) probably haven't yet triggered any thermal reactions in the software, have they?

Here it's 30°C, we were at Lake Constance today at the swimming area . The car feels like chewing gum (compared to cooler weather).

In my opinion, the turbocharger's boost build-up is too slow. Please check if anything is loose on the wastegate linkage or if there is any play in the lever.

Logs do not need to be converted, and they should not be.

Best regards, Rainer.

Thank you for your help – the wastegate valve has some play, which is causing the noise.
Werde dann wohl nicht drumrumkommen, den Lader auszutauschen.

What's also puzzling me is why I can't reach the top speed. (I'm about 15 km/h short). Because at higher RPMs, the turbo boost pressure seems to be correct.

Hello,

It seems that a certain amount of rattling is normal, but the question is how much play there is.
"There might be another issue: is the intercooler system sealed? What do the additive and multiplicative adjustments of the lambda control indicate in the measurement blocks within the engine control unit?"

Maximum air mass values when compared to a vehicle of the same type?

Best regards, Rainer.

Hello, and I'm sorry for not getting back to you sooner.
The turbocharger will likely be replaced or the wastegate repaired within two weeks, if possible. We'll take a look after it's removed.

This morning on the A2 highway, I had the opportunity to record some measurements at a higher (almost maximum) speed. An excerpt from the drive is attached.

"The loss of boost pressure is not noticeable at higher engine speeds. Could it be possible that the pressure behind the throttle valve is being lost through the crankcase ventilation system, and therefore the loss of boost pressure is not measurable?"

The lambda values seem plausible to me. Is a multiplicative adjustment factor of -5.1% to -5.5% (across the board) acceptable? Do I need to perform any further tests to rule out the pre-cat converter?

The maximum air mass flow rate of 166 g/s seems okay to me, but I don't have any comparison values.

So, where does the power go in 6th gear? In 5th gear, I reach the same speed...

that the pressure behind the throttle valve is lost through the crankcase ventilation system.


I haven't looked at the system in detail yet, but I've heard several times that the valve inside the valve cover sometimes causes problems. That's why Americans often modify these machines to use an 'open' venting system and block off the connections to the air intake side.

The crankcase ventilation system should be checked before the timing light test.

maybe/sort of/kind of.

'My car (CCZB, manufactured in 2010) has a hose to the intake manifold before the turbo and another one connected to the intake bridge. I wonder if all of them are supposed to have these... There's an oil separator and a diverter valve in the valve cover that, depending on the pressure, directs the flow either towards the intake bridge or towards the turbo. I know of at least one case where this happened and the engine was running terribly... It was sawing during idle, occasionally triggering warning lights, and experiencing jolts during acceleration, etc. I need to do some more research on that.'

Hello!

On a related note:
Today, I removed the turbocharger from an Audi A4 with a 1.8T engine because the motor was producing low and uneven power.
The noise and rattling coming from the turbo were another defect.

Upon inspection, it was evident that the wastegate valve mechanism in the exhaust area was completely loose.
on the verge of collapse.

Last week, I finally received the new turbocharger. As suspected, the wastegate lever was completely corroded. With the new turbocharger, driving is now much more pleasant, even in higher gears. The vehicle feels noticeably more responsive throughout the entire RPM range, and the noise is completely gone.

Last month, I also installed a PCV fix that modifies the crankcase ventilation system to prevent any loss of boost pressure. I can't say for sure if it made a difference, but now I definitely reach the top speed. My guess is that the valves and injectors were heavily carbonized due to frequent short trips, and they are slowly starting to verschandeln themselves out again.

I will continue to monitor it, but for now, I am quite satisfied. The car is really fun to drive .

Thank you for the feedback!