Weird Boost Problem..Help!!

[NoahY03]

2007 VW GTI, Stage 1

I start my car and I drive and it's perfectly fine, I'm able to hit my usual boost which is 15PSI and I have no issues. If I leave the car idling for a little bit or turn it off and turn it back on, my turbo caps at 4PSI and it just sounds like it's stuck and can't hit anything past it. Sometimes it comes back to normal but that's very very rare..The only time it comes back to normal is the day after I drive so roughly every 24hrs. I replaced my PCV valve and I don't think I got any new codes. What could be the issue?

 

[ROH ECHT]

So, it appears to be obvious you have no way for doing any data reading and you only have a boost gauge.

What you can do is check its N75 resistance with a multi-meter. If it is not at 25 ohm, ±1 ohm, then replace it. It can cause weird boost issues when 2 or more ohm off from 25. The risk is that it may be something else if you choose not to do so yourself, or to not have it properly diagnosed. Could be a mechanical WG(waste-gate) issue where the WG hangs up at certain temps and remains open. Or its linkage may be loose at the adjusting nuts connecting the WG linkage to the WG actuator rod...allowing it to catch and not close. So, inspect the linkage if you know what you are looking for.

 

[NoahY03]

So, it appears to be obvious you have no way for doing any data reading and you only have a boost gauge.

What you can do is check its N75 resistance with a multi-meter. If it is not at 25 ohm, ±1 ohm, then replace it. It can cause weird boost issues when 2 or more ohm off from 25. The risk is that it may be something else if you choose not to do so yourself, or to not have it properly diagnosed. Could be a mechanical WG(waste-gate) issue where the WG hangs up at certain temps and remains open. Or its linkage may be loose at the adjusting nuts connecting the WG linkage to the WG actuator rod...allowing it to catch and not close. So, inspect the linkage if you know what you are looking for.

Could you tell me where the N75 is on a '07 GTI? I can't seem to find it online or anything--also I really appreciate the reply

 

[ROH ECHT]

N75 is mounted on the turbo. It has a wiring connection. Unplugged, you'll see two tabs inside the plug on the N75. Connecting to those two tabs are where you would test its resistance.

Try adding mk5 gti to all future searches;

Here are some documents for the BPY-EA113 engine;

EA113 engine;
http://www.volkspage.net/technik/ssp/ssp/SSP_337.pdf

EA113 fuel system;
http://www.volkspage.net/technik/ssp/ssp/SSP_334_d1.pdf

EA113 (BPY engine) torque specs...just be sure you are in the correct section as there are other engines in this;
https://blogvager.files.wordpress.com/2012/01/10-audi_a3_qsb_web.pdf