p0299 underboost code, does it always mean the turbo is bad?

[PappySmearnoff]

Hey again folks. I would like to get my a4 back on the road but the p0299 code keeps getting thrown and the car is really slow now. My brother had it for years and had some boost leaks in the past but were fixed by patching some vacuum lines or something I'll have to ask. This new problem however doesn't seem so simple. The vehicle doesn't boost much and has a rough idle. I took out my forge splitter and took it all apart, I soaked all the parts in kerosene for a day and then lubricated each piece with white lithium grease and put it back together properly. I haven't been able to test if the code will come back since it's unregistered but it is definitely still limping. Does this always mean the turbo has gone bad if it's not the diverter valve?

[dalazybastard]

Rough idle = Vacuum Leak

Underboost = boost leak.


You have a leak somewhere.

Try unplugging maf and see if idle improves. (Do not drive) This is done to see if there is a Vacuum leak and if there is it should run better.

Then hunt for that leak. A pretty good guess is your SJP as they tend to fail on the seal where the part is assembled.


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[PappySmearnoff]

https://gyazo.com/dde662accd5e6970e2964d1d45bcb2fa

is the suction jet pump this thing?

[jpulll]

https://gyazo.com/dde662accd5e6970e2964d1d45bcb2fa

is the suction jet pump this thing?

Yupp, see how this one is split open?

IMG_0344.JPG

Another thing to keep in mind is our cars on stock tunes (or stage 1-2) don’t generally like splitter valves or blow off valves. A diverter valve is the way to go. The ecu is expecting to see a specific amount of volume of air. With blow off valves/splitter valves, you lose that volume and the ecu can’t necessarily compensate for it, unless you’re obviously tuned for it. These ecu’s are very smart and are able to compensate in a variety of ways, but with those BOVs/splitter valves, it’ll just think it’s loosing air somewhere and throw a code or go into limp mode.


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[tate182]

Reviving this thread because I have an under post condition and the car is idling rough I found a crack in one of my breather hose through a smoke test replaced the Pcv and updated the DV valve to the new piston style I can’t figure out what the problem is I’m on a stage 1+ tune( Downpipe, intake) I should be boosting 22psi peak and can not make it that high. There were no problems with the car before the tune

Didn’t realize this was the b6 forum k have a b7 a4 2.0t if the mods want to delete this

[jpulll]

Could be the wastegate needs adjusting. My k03 wouldn’t boost past 19 even tho I should have had the 22psi like you say. I never truly figured out if it was the wastegate, but that’s what I attributed it to because I didn’t have any leaks, and my turbo still seemed sound (no hairdryer sound during spooling). Also what others/motoza told me it could be. Food for thought.


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[tate182]

Could be the wastegate needs adjusting. My k03 wouldn’t boost past 19 even tho I should have had the 22psi like you say. I never truly figured out if it was the wastegate, but that’s what I attributed it to because I didn’t have any leaks, and my turbo still seemed sound (no hairdryer sound during spooling). Also what others/motoza told me it could be. Food for thought.


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I was going to do that until I had a new problem come up that is going to cause me to have to rebuild the engine probably


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