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Need your guys help & expertise please

I've been trying to find the cause of the P0299 underboost code for a while now and after randomly stabbing in the dark by changing intercooler, Y-piece, hoses, N75 valve, I read a really good post on here (in the 996 section) about pressure testing.

I've spent the last few weeks, getting a gauge, schrader valve, fittings, and various sizes of hose so I can T into the lines of the turbo system (it was the offside turbo to bottom of the N75 I actually Tee'd into) and yesterday, tried to test the system using my compressor.

The more I think about it, I now realise that I would have to plug both of the airboxes and the throttle I think.

Has anyone performed an intake pressure test on a Cayenne Turbo on here?

If so, What is the best hose to T into?

How many hoses do you have to block off?

Do I have to remove the throttle body and blank behind it?

Thanks in advance

Chris

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I think you're going about this the wrong way, you risk damage to components by using too much air pressure and throwing parts at a vehicle in the hopes of repair is the worst thing to do. I recommend having the system smoke tested to locate leaks. That code can be caused weak divertor valve, waste gate control or once I had a MAF sensor cause this issue with fuel trim codes.

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I think you're going about this the wrong way, you risk damage to components by using too much air pressure and throwing parts at a vehicle in the hopes of repair is the worst thing to do. I recommend having the system smoke tested to locate leaks. That code can be caused weak divertor valve, waste gate control or once I had a MAF sensor cause this issue with fuel trim codes.

Hi wvicary, I thought that too, that's why I am only going to 1 bar, as the system is apparently good for 1.1 bar. I also have a relief valve in there too.

I have no one to go to that is able to do a smoke test, and the leak is so small, and so intermittent, I doubt it would show up.

What do you mean by divertor valve? Do you mean dump valve?

waste gate control valve? N75?

it's starting to do my head in, and I have to catch it in the summer, or the problem disappears in the cold of the winter. The problem is that the engine bay is stuffed so full, it's not easy to see parts and look for problems.

Chris

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Do you have access to a vacuum pump with a gauge? Connect it to the waste gate in question and note the amount of vacuum needed to operate the waste gate control rod a said amount. I have seen them bind and also the vacuum pot corrode. When the pot corrodes the rust/debris will be drawn into the control solenoid and cause intermittent issues.

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Do you have access to a vacuum pump with a gauge? Connect it to the waste gate in question and note the amount of vacuum needed to operate the waste gate control rod a said amount. I have seen them bind and also the vacuum pot corrode. When the pot corrodes the rust/debris will be drawn into the control solenoid and cause intermittent issues.

Is the vacuum pot for the waste gate a replaceable part ?

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