mk4 GTI only hitting 5psi?

[Feeine]

ok so it started after i tucked my amp wiring into the channel with engine loom and removed the lower piece of airbox. (Has a pod) idling is jumpy, high, and will only boost to 5psi. unfortunately i didn't have a boost gauge when it was running fine so im not to sure on what psi it was. definitely higher though.
Here is what i've done/checked.

MAF is fine
N75 Unplugged yields 4psi (guessing wastegate pressure?)
DV is not leaking.
Fixed small vacuum leak on booster line.
Cleaned throttle body as it was dirty. (Seemed to fix jumpy idle)
No boosts leaks anywhere to be found.

Done alot of research to find no one with symptoms the same as me. Starting to get a little frustrating. anyone got any suggestions for what has gone wrong?

[h100vw]

ok so it started after i tucked my amp wiring into the channel with engine loom and removed the lower piece of airbox. (Has a pod) idling is jumpy, high, and will only boost to 5psi. unfortunately i didn't have a boost gauge when it was running fine so im not to sure on what psi it was. definitely higher though.
Here is what i've done/checked.

MAF is fine
N75 Unplugged yields 4psi (guessing wastegate pressure?)
DV is not leaking.
Fixed small vacuum leak on booster line.
Cleaned throttle body as it was dirty. (Seemed to fix jumpy idle)
No boosts leaks anywhere to be found.

Done alot of research to find no one with symptoms the same as me. Starting to get a little frustrating. anyone got any suggestions for what has gone wrong?

Have you scanned it with VCDS. not sure what it might find but should be done on the off chance. Also that 4 PSI seems pretty low for actuator pressure to me. Have a look at the nuts on the actuator rod. Are they loose?

[Feeine]

Have you scanned it with VCDS. not sure what it might find but should be done on the off chance. Also that 4 PSI seems pretty low for actuator pressure to me. Have a look at the nuts on the actuator rod. Are they loose?

I'm gonna limp it to work tomorrow so i can throw it on the hoist and have a good look. will also scan it to be sure.

[gldgti]

You say maf is fine.... Are you sure? Check the wiring harness etc?

[Bug_racer]

Crimp the hose going to the wastegate . If you still cant get more than around 10 PSI you have a turbo/blocked exhaust/boost leave etc issue

[Feeine]

Have you scanned it with VCDS. not sure what it might find but should be done on the off chance. Also that 4 PSI seems pretty low for actuator pressure to me. Have a look at the nuts on the actuator rod. Are they loose?

Scanned it last night, got a few codes including 2 for the N75. did as bug_racer suggested and bang. Hit's 10psi and will keep climbing easy. so n75 it is. >.<

[theBRUCEofWAYNE]

Crimp the hose going to the wastegate . If you still cant get more than around 10 PSI you have a turbo/blocked exhaust/boost leave etc issue

Hey bug, got a similar issue myself. Can you or anyone on this thread upload a pic of the wastegate line to crimp? Thanks


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[theBRUCEofWAYNE]

Sorry excuse my ignorance. It's this one isn't it?


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[h100vw]

Yes mate.

[theBRUCEofWAYNE]

Yup ok crimped the pipe at the end closest to the actuator with some vise grips. My ecu is slightly tuned. Before crimping it read at 8 psi. When crimped, reads at 12psi. n75 is rooted. Thanks dudes!


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[theBRUCEofWAYNE]

New update. Bought a brand new, fresh-out-of-the-box n75 from ecs. Replaced it with my original one. No change!!!. Still getting **** psi. No boost leaks either. Dad made me this fitting. Happy to lend to anyone in need on watercooled. So what do you suggest I try next? (before taking it to a VW place)


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[tmh983]

instead of crimping the wastegate line, just disconnect it all together (so the wastegate is line is open to atmosphere), carefully test drive it, the turbo should be trying to boost its tits off (you should be able to get miles more than 12psi), you will know it straight away so let off the throttle so as not to damage anything.
If it still won't get past 12psi then i'd start by making sure the wastegate actuator is correctly tensioned, after that you either have a blocked exhaust or a failed turbo...

[theBRUCEofWAYNE]

instead of crimping the wastegate line, just disconnect it all together (so the wastegate is line is open to atmosphere), carefully test drive it, the turbo should be trying to boost its tits off (you should be able to get miles more than 12psi), you will know it straight away so let off the throttle so as not to damage anything.
If it still won't get past 12psi then i'd start by making sure the wastegate actuator is correctly tensioned, after that you either have a blocked exhaust or a failed turbo...

Yup thanks tmh. I was hitting 90kpa=12psi with crimped hose. Will see where it goes with the hose off. I also think the actuator is rooted or something near it. Cheers bro!


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[tmh983]

The other possible thing it could be is a serious fueling problem letting it go lean. We saw it on an old 200sx that had a faulty AFM, the air fuel ratio would go to 17-18:1 at full throttle, the engine would still run, but it was struggling to build up boost.
This is obviously very bad and a very real risk of melting a valve or smashing a piston...

[h100vw]

Is that N75 fitted correctly? The longest pipe should go into the TIP.

mbc to n75 - The Mk2 - Edition 38 Forums

Gavin