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Loss of boost and possible fuel cut?

Tiny
BARDOCKOBAMA
  • MEMBER
  • 2013 VOLKSWAGEN GOLF
  • 2.0L
  • 4 CYL
  • TURBO
  • 4WD
  • MANUAL
  • 197,000 MILES
A little background. It's a 2013 Golf R I have simple bolt-on (intake, upgraded HPFP, intercooler, recirculating oil catch can, etc, ) and a stage 2 tune by IE. 197000 miles, but the engine is relatively new and was replaced at 160000. The issue I've been having is relatively new. On to the issue then. Past few months.

At WOT, my boost tanks around 5,000 RPMs. It'll hit full boost for half a second and then timing is pulled, and I lose boost. Building the boost is no problem, and as long as I don't floor it, I can be in boost and sustain it to redline. So, any help you can provide would be amazing.
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Friday, December 29th, 2023 AT 6:29 PM

23 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,959 POSTS
It sounds like the turbo is going out or the exhaust system is partially clogged. I would use this guide to test the catalytic converter and we should run the codes as well. Also please remove the inlet or outlet of the turbo to check the turbo main shaft endplay.

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

and

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

The turbo will boost at low RPM when it goes bad, also if there is engine oil inside the inlet tubes the turbo is bad. Here is how to replace the turbo and check the tubes and endplay. Check out the images (below). Please let us know what happens.
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Saturday, December 30th, 2023 AT 12:22 PM
Tiny
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  • 14 POSTS
I was afraid that might be the case. I do have oil in my inlets and oil tends to get the MAP sensor very dirty and I have to clean it occasionally.

However, I do have to add that I have no engine codes for this or anything else.
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Saturday, December 30th, 2023 AT 12:51 PM
Tiny
KEN L
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Yep, it sounds like the turbo is no good. It may not have a code for this which is normal. Please check the turbo main shaft endplay which will tell you for sure.
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Sunday, December 31st, 2023 AT 1:36 PM
Tiny
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  • 14 POSTS
Okay, so I am reviving this because I finally was able to replace my turbo with a known good OEM one and a brand new N75 valve too. The old turbo was definitely bad. It was praying oil everywhere, the shaft had a ton of play, and one of the tips of the compressor fins was even bent.

However, while the car drives 100% better, I still can't seem to go past 5k RPM at WOT without the boost dropping off completely and losing all power. I'm kind of at a loss here.

I can get up to redline at basically any boost level but if I try to do it at max, I can't seem to.
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Wednesday, February 14th, 2024 AT 1:48 PM
Tiny
KEN L
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It sounds like you have a clogged exhaust system, plus have you run the codes?

Here are two guides to help us see what's going on:

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

and

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Please let us know what happens.
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Thursday, February 15th, 2024 AT 7:54 AM
Tiny
BARDOCKOBAMA
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  • 14 POSTS
My exhaust is catless with a single resonator from the downpipe to the muffler. Everything is 100% clear, as I just finished checking it. However, I can't check the muffler without disassembling it or just buying a new one. Any suggestions? Could the muffler be clogged?
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Thursday, February 15th, 2024 AT 11:13 AM
Tiny
BARDOCKOBAMA
  • MEMBER
  • 14 POSTS
Quick update:

I removed the muffler, so it was just straight piped. The problem was still present. So, that rules out a clogged exhaust. Any other ideas as to what it could be?
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Thursday, February 15th, 2024 AT 2:50 PM
Tiny
KEN L
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A bad MAF sensor can cause this problem which can happen after a bad turbo, do you have any codes? I would try swapping the sensor out. Here is the location. Check out the images (below). Let us know how it goes.
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Friday, February 16th, 2024 AT 10:17 AM
Tiny
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I replaced the MAF sensor, and the problem is still there.
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Saturday, February 17th, 2024 AT 10:22 AM
Tiny
KEN L
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When you say it cuts boost after 5,000 RPMs, are you driving the car or just sitting still revving the engine? Also, are there any engine noises such as a rattle or ping? Can you do a live data scan so I can see the numbers?
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Monday, February 19th, 2024 AT 8:37 AM
Tiny
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I'm actually driving the car. If I go wide open throttle, I just lose power past 5,000. There are no misfires that happen when this occurs. Feels like the boost is cut and the timing is retarded. I do have a live data feed on my car watching the boost, timing, misfires and more. I can get a video and show you.
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Monday, February 19th, 2024 AT 8:46 AM
Tiny
KEN L
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That would be great! This way I can see what's going on. Can you check the vacuum line going to the vacuum diaphragm? I am thinking the vacuum diaphragm could be bad as well, can you please re-run the trouble codes as well? Here is the valve so you can see what I am talking about. You might want to see if it holds vacuum. Check out the images (below). Please let us know what happens.
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Monday, February 19th, 2024 AT 9:06 AM
Tiny
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The only code I have is P0036, and it's for my rear O2 sensor. More specifically, it's a code I'll always have because the wires to that sensor are fried. They shorted on a 300 mile road trip in some deep snow. Otherwise, I have no codes active or pending.

As far as I can tell, the vacuum line is secure and fine. But it looks like the diagrams you gave me are for a MK6 GTI, where I have a MK6 Golf R. It doesn't have the same engine.

And I can go past 5k RPM just fine as long as I'm not trying to floor it. I can go all the way to the red line. I just can't get there by going WOT.

I'm attaching a video showing the live data readout while I'm flooring it.
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Monday, February 19th, 2024 AT 4:34 PM
Tiny
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You can hear where I punch it. When the sound stops, I'm not lifting off the throttle. I lift off about a second or so after it stops accelerating.
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Monday, February 19th, 2024 AT 4:36 PM
Tiny
KEN L
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Thanks for the video. It seems like you have a restriction in the air intake of the engine, or the low-pressure fuel pump is getting weak. Is the power okay up to 5,000 RPMs?

Here is a guide to help and instructions for your car in the images below:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Delivery Pressure:

Test Conditions:
The fuses must be okay.
Battery voltage must be at least 12 volts.
All electrical consumers such as, for example, lights and rear window defogger, must be turned off.

Start the engine and run at idle speed.
Close the shut off valve "B" for a maximum of 15 seconds and read the pressure on the Pressure Tester (VAS 6551) :

Specified value .................... 0.5 bar (7.25 psi) minimum

Auxiliary Fuel Pump (In-line Fuel Pump) Pressure:

Test Conditions:
Battery voltage is at least 12.5 volts
The fuel filter is okay.
Fuel tank: Fuel level, min. reserve.
The ignition is off.

Connect the vehicle diagnostic tester and perform the guided function "Check Electric Fuel Pumps".

The fuel pump now runs for 30 seconds.
Let the fuel pump run until the highest fuel pressure is reached.

Specified value .................... at least 3.5 bar (50.7 psi)

Fuel Delivery Quantity:

Test Conditions:
The fuses must be okay.
Battery voltage is at least 12 volts

Specified value .................... at least 1000 ml/30 seconds

Check out the images (below). Please let us know what happens.
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Tuesday, February 20th, 2024 AT 10:53 AM
Tiny
BARDOCKOBAMA
  • MEMBER
  • 14 POSTS
I haven't had time to test the low pressure fuel pump yet, but I doubt that would be much of an issue as it only has 20k on it. I bought a brand new one a while back.

The only thing I can think on the fueling side that might be failing may be the HPFP, it's an aftermarket APR unit that has about 90k on it. I'll need to test it though.

However, on the intake side, I removed the filter completely to see how it performed and I now can get reliable, full boost at WOT up to 6k RPM. Not quite to redline, which is 6.5k, but that's vastly improved. I'll be replacing that filter. It has over 100k miles on it, and I've been cleaning it at every oil change.

And to answer your question, the power is fantastic until it hits 5k (6k with a good filter/no filter now). I'll be doing a deeper clean on my current filter until I get a replacement.
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Wednesday, February 21st, 2024 AT 11:01 AM
Tiny
BARDOCKOBAMA
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I also wanted to ask if it's possible that my fuel injectors might need to be replaced? I'm not sure if there's a test for that or not. They're stock and have 201k on them.
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Wednesday, February 21st, 2024 AT 6:45 PM
Tiny
KEN L
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Usually one will go out at a time, but if this is a performance application then the fuel volume may need to be increased. A weak HPFP can cause this issue as well.
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Thursday, February 22nd, 2024 AT 11:36 AM
Tiny
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  • MEMBER
  • 14 POSTS
Is it possible that my throttle body is the issue? The throttle body is stock, and has over 200,000 on it. I noticed that when it warmed up here (90°+) that I was able to take it to redline. The reduction in air density might have allowed me to do that. I wanted to field that as an idea since I don't think it's my HPFP. That only has 70,000 on it and it's an aftermarket APR unit.
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Wednesday, April 17th, 2024 AT 10:26 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
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Usually when the throttle body has a problem the car will go into limp mode and give a code, but you never know. You can give it a try and see what happens. I have seen the tune cause this problem, can you take the tune out and leave a stock tune in to see if the problem goes away?
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Thursday, April 18th, 2024 AT 9:49 AM

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