Boost no more

[b5a4erik]

fwd 1.8t aeb

Car simply does not boost.

sooommmetimes makes it to 1psi.

is this just a huge boost leak or something else such as limp mode?

Regards,

~ ea

[SacSantorin]

Scan with Vagcom and do a Boost leak test. It will answer both questions. If you're boosting 1 psi i would say you have a major leak. Limp mode leaves you around 5 psi. You could have both thoughso make sure to do both.

BTW...I grew up off Sumner Ave....small world...

[woolveren]

This happened to my car few months back, but it was a blown fuse cutting N75.

[pgiuliano98]

Does it make a supercharger whine by any chance? My car seems to have lost its 'umph' from boost as well and I'm curious as to why.


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[thrilos5]

Need more details to help you out

[b5a4erik]

Scan with Vagcom and do a Boost leak test. It will answer both questions. If you're boosting 1 psi i would say you have a major leak. Limp mode leaves you around 5 psi. You could have both thoughso make sure to do both.

BTW...I grew up off Sumner Ave....small world...

Word! Good stuff man, happy to be keeping the b5 around!

As for the other commentors, thanks guys!

I'll check out that n75 fuse, then boost leak test if that's not the case. Need to get Vagcam :/ Doesn't make a supercharger whine, sorry pg, good luck though. And thrilos5, your emblem makes me smirk ;) Love for all teh cars.

[b5a4erik]

This happened to my car few months back, but it was a blown fuse cutting N75.

Hey woolveren,

Which fuse is it? #29?

` ea

[SacSantorin]

Hey woolveren,

Which fuse is it? #29?

` ea

It is fuse 29 but I doubt that's your problem. Fuse 29 is for n75 n80 and something else I can't remember so if it was blown you would be having other problems as well. Do you have a boost gauge installed? What does your idle vacuum look like?

[b5a4erik]

I do have a boost gauge, I think vacuum is normal.

I figured the simple fuse would be the first place to start...

Will check it out tomorrow, the fuse and where my vacuum is @.

[woolveren]

Hey woolveren,

Which fuse is it? #29?

` ea

Yeah it was fuse #29 from what I remember.. As SacSantorin said, you would have got a CEL or other problems if it was really a blown fuse #29 as there are other electronic devices such as MAF and Leak detection pump connected to it as well.

[walky_talky20]

The wastegate flapper may have physically fallen off the turbo. Everything will be fine, except no boost at all. This failure is not uncommon for the early K03-005 on the AEB engine. The later K03-029 variant from the ATW, AWM, and B6 AMB does not have this failure as often, and is a little bit of an upgrade in terms of flow.

[b5a4erik]

The wastegate flapper may have physically fallen off the turbo. Everything will be fine, except no boost at all. This failure is not uncommon for the early K03-005 on the AEB engine. The later K03-029 variant from the ATW, AWM, and B6 AMB does not have this failure as often, and is a little bit of an upgrade in terms of flow.

I'm hoping that isn't the case. I had this problem before, where it would rattle like a leaf in a bike wheel on decel...

Replaced it with a rebuilt k03.

Diagnosis needed.

[walky_talky20]

You can disconnect or pinch off the pressure line to the wastegate actuator, then carefully drive the car to see if boost is attained. Boost is completely unregulated, so drive easy and try it in 4th gear or something. Boost will build more slowly and safely that way.

[b5a4erik]

So if I do this, and I get boost, it means my wastegate is intact?

[walky_talky20]

Yes. That diagnosis would conclude the flapper is fine, and further that the actuator is most likely fine, too.

Your problem would then be isolated to some reason that the actuator is getting more pressure than it should. The N75 is supposed to divert the pressure away from the actuator. So either:

- the N75 is not being signaled (ECU output disabled [limp mode])
- the N75 signals are not making it to the N75 valve (ECU output circuit dead, wire broken, fuse blown, etc)
- N75 is being signaled but isn't actually doing anything (N75 is electrically open or is physically stuck internally)
- N75 is actuating properly, but the pressure simply cannot divert (N75 dump to the inlet pipe is blocked or restricted)

[b5a4erik]

You walk the talk,

thanks man.

Will give this test a go.

[b5a4erik]

So I pinched it off, same thing: No major boost, 0, 1, tapped out @ 2psi after a good while.

So basically, blown waste-gate?

[walky_talky20]

Seems that way, yes. You can drop the cat off the turbo and have a look-see.

[b5a4erik]

hm, indeed.

[OverSpun]

What is your vacuum showing @ idle? Should be ~20hg If not, your check valves and/or jet suction pump could have failed. All of those are plastic and they need to be replaced eventually since they become brittle.

[b5a4erik]

Yeah, at idle I'm @ -20hg. I plan on replacing all those little check valves sometime though, due to previously mentioned reasons.

- - - Updated - - -

Would a bad check valve cause a high idle? ~1100rpm

[OverSpun]

Yeah, at idle I'm @ -20hg. I plan on replacing all those little check valves sometime though, due to previously mentioned reasons.

- - - Updated - - -

Would a bad check valve cause a high idle? ~1100rpm

I think bad check valves would show you a low vacuum @ idle. That is when I replaced all of mine since I was also getting MILs from them. Do you have a VCDS if not, order one asap- http://www.ross-tech.com? You need to scan the car to correctly diagnose many issues. Could be a failing MAF.

The car should idle high when its cold but it should drop down after the startup.

[SacSantorin]

did you ever figure out this issue?

[b5a4erik]

did you ever figure out this issue?

I've been dealing with a couple of problems with my car:

1. Leaking Power Steering Rack
2. Turbo

And this has been happening just as of late, so it's all kinda hitting me right now.

I got this, though.



~ ea