Mild vacuum leak causing major loss of power.

[Duchenbagen]

Over the weekend my car developed a vacuum leak accompanied by a wonky idle. I checked all the usual suspects. The car is a 1.8T APR stage 3+ 6MTQ. It’s usually hyper. Now it can’t get out of its own way. Weird side note pressing the brake pedal makes the idle smooth out momentarily. Any insight old guy?

[Akabetterthanu]

Not oldguy but it could be check valve related since you mentioned the brake thing. Just my 2 cents


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[old guy]

Check the vacuum line from the intake to the N249 and the line from the N249 to the DV. A leak in either of those hoses will causer the DV to open at its spring pressure since it will no longer have a boost signal to help keep it closed under boost.

This will cause a loss of performance as well as a rough idle.

[EuroxS4]

Sounds like a failing SJP. They normally come apart at the seam where they are fused together. Check there as well. Normally they come apart under boost.

[Duchenbagen]

All right, Checked the the N249 valve line. its all intact... At idle the car is drawing 14 inHG it usually pulls 18-19 inHG. I just replaced the SJP and all the hoses attached to it to try to remedy this situation. No dice.

[old guy]

All right, Checked the the N249 valve line. its all intact... At idle the car is drawing 14 inHG it usually pulls 18-19 inHG. I just replaced the SJP and all the hoses attached to it to try to remedy this situation. No dice.

Clamp off all of the vacuum hoses connected to the intake manifold, one at a time. See if clamping one of them increases your vacuum at idle.

[Duchenbagen]

Clamp off all of the vacuum hoses connected to the intake manifold, one at a time. See if clamping one of them increases your vacuum at idle.

I will get on it. Thanks.

[BumblebVR6]

I’ve been having a similar issue. Same car with same turbo kit basically. Most times, the vacuum will sit at the usual 19-20” then jump around at a red light. Had a open circuit on cylinder one that was causing a cel to come on due to misfire. I changed the harness and light has been off for over a week and no more misfire codes. I have a 034 billet pvc valve and have read these can cause issues? Checked everything else and didn’t find any broken hoses. Will remove the sjp and have a look at it. Think I have a spare one.


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[EuroxS4]

I will get on it. Thanks.

If this fixes your issue then you have a bad or failing pcv valve.

[Duchenbagen]

If this fixes your issue then you have a bad or failing pcv valve.

Hmm, I have the 034 PCV replacement with the billet valve. It’s only got 10K on it. I hope that isn’t the issue. Also, the EGR is deleted and capped off.

[A4SoftWalker]

Just throwing this out there for our generalized knowledge base:::

There was a known problem with the spring pressure of the initial batch of 034 billet PCV valves.
When did you order yours?
Also possible the problem is recurring in another batch.

Also check out the bleeder valve (another name for the PCV valve) information for different year models in Thomas (A4 Darkness) thread here >>> https://www.audizine.com/forum/showt...=1#post6016725

With this new information when replacing the PCV ensure you have the correct one for your year of manufacture/VIN.

[A4SoftWalker]

Hmm, I have the 034 PCV replacement with the billet valve. It’s only got 10K on it. I hope that isn’t the issue. Also, the EGR is deleted and capped off.

If memory serves this is how the wrong billet PCV behaved back in the day. It would run fine for a while and then fail or rather cause running issues.