Annoying P0299 (Ive searched the entire web)

[Johann2.7t]

Hey guys looks for a bit of help with a p0299 code that will not go away.

To start, Ive boost leak tested up to about 20 psi and through that testing found and replaced many leaks/parts. The car now holds pressure very well so i feel thats ruled out.

A new OEM N75 was installed after much reading and most people seemed to point this way.

I have ran a few logs with vag com although I'm quite new to logging. The car is requesting upwards of 25psi but only receiving around 15psi. I have converted specified (~2500mb) and actual (~1900mb) by subtracting my engine off actual (820mb @ 5500' elevation or so) and multiplying by 0.0145?. These numbers seem very high to me on what i truly believe to be bone stock A4.

This morning I have disconnected the wastegate line to the N75 and had a drive. I was nervous about giving it too much throttle so Im not sure I accomplished much but it did seem to build boost easier and slightly higher numbers in my logs.

The n75 meters correctly ~32ohms if memory serves and logs show duty cycle in the 80% range at WOT when connected properly.

Very lost as what to try next.

help?!

[MurkyRivers_A4]

Ah yes, I had this same issue.

My requested boost was more in line with my tune and not shooting for 25psi, but my issue was the WG actuator adjustment. It was too lose. I took the exhaust manifold off, adjusted the waste gate rod using the 2 turn method and its been good ever since.

I was fighting this issue for the whole time I owned the car, uh 10 months maybe?, and just figured it out after throwing many parts at it.

[Johann2.7t]

Ah yes, I had this same issue.

My requested boost was more in line with my tune and not shooting for 25psi, but my issue was the WG actuator adjustment. It was too lose. I took the exhaust manifold off, adjusted the waste gate rod using the 2 turn method and its been good ever since.

I was fighting this issue for the whole time I owned the car, uh 10 months maybe?, and just figured it out after throwing many parts at it.

any more info on this method?

is there a concrete way to test this with the turbo out of the car? I have a spare turbo is why i ask.

also how can i confirm if the car is tuned or not, it certainly doesn't feel like it nor would i expect the previous owner to ever consider chipping it (older, no nothing about cars type)

Lastly if the car develops more boost with the wastegate line undone from the N75 doesnt that rule out problems with the wastegate?

[MurkyRivers_A4]

any more info on this method?

is there a concrete way to test this with the turbo out of the car? I have a spare turbo is why i ask.

also how can i confirm if the car is tuned or not, it certainly doesn't feel like it nor would i expect the previous owner to ever consider chipping it (older, no nothing about cars type)

Lastly if the car develops more boost with the wastegate line undone from the N75 doesnt that rule out problems with the wastegate?

Loosen the nut closes to the waste gate actuator on the actuator rod. Firmly press the flapper arm in the closed position then hand tighten the nut furthest from the actuator on the rod. Once hand tight, use a wrench and rotate the nut 2 full rotations to tighten. This will set the WG preload. There is another way to do it with supplying air to the WG actuator but I had no way of limiting 4psi for crack pressure.

Usually if it is requesting boost over 9-11 psi, it is tuned. I cant imagine any other scenario where the ECU would be requesting more than the car can handle stock.

With the air supply disconnected from the WG actuator, you will definitely get more boost as the WG can only open with the pressure from the exhaust, which usually wont happen at all.

If you bypass the N75 and hook the supply line directly to the actuator, you will only get whatever the crack pressure is, so 4-5 psi.

[MetalMan]

If you bypass the N75 and hook the supply line directly to the actuator, you will only get whatever the crack pressure is, so 4-5 psi.

A simpler way to run this test is to unplug the electrical connector from the N75. You'll get a fault code for the N75 being disconnected of course, but as Murky pointed out checking wastegate cracking pressure is a good test to perform.

[Johann2.7t]

A simpler way to run this test is to unplug the electrical connector from the N75. You'll get a fault code for the N75 being disconnected of course, but as Murky pointed out checking wastegate cracking pressure is a good test to perform.

so not to sound like total idiot but what will this test confirm? The wastegate is supposed to crack open at 4-5 psi?

[MetalMan]

so not to sound like total idiot but what will this test confirm? The wastegate is supposed to crack open at 4-5 psi?

It just confirms the wastegate setting is where it should be (4-5psi crack pressure).