Hello All, I have been lurking and found many of the threads here very useful. I'm getting a bit frustrated and hoping for some pointers...
I got the wife an 03 Audi A4 quattro (AMB if memory serves). It has the P0299 code and doesn't boost past 7psi or so as read by vagcom at the MAF. So far I replaced the DV, N75 valve, and tried temp skipping the N249. Same boost. Did leak test and only thing I noticed was a concerning amount of air coming through the oil filler cap opening and the disconnected pancake valve near the MAF/N75... but I did not make sure all the valves were shut either so it was not perfect test... although I didn't find any sounds or air from obvious large hose leaks when pushing over 10psi into it.
So today I was thinking about this oil filler cap air. With car warmed at idle I removed the oil cap, just sat it on its opening and it had enough positive pressure to jumpjumpjumpjump. :/ I unfortunately do not understand this cars PCV system especially with all the other systems in close proximity/connection. Dip stick did not seem to have this pressure, I think its in my valve cover area.
Does anyone know how it would become pressurized here? Particularly I am interested in if this could be where the boost is going and what path it would need to take... Any diagrams of this system for this engine would also be very helpful.
Yes the PCV valve is bad. You need to replace all the breather parts located under the intake manifold. Go to ECS tuning and go to engine, and then emissions. Then PCV. You will see all the parts. Depending on what your engine happens to have, there will be the big plastic pipe coming out of the block, the PCV valve, a rubber Tee, and on some the pipe running from the PCV to the 3 way Y hose at the back of the valve cover thats made of plastic. They all must be replaced together if its the type with the PCV valve with 4 nipples on it because you use a heat gun and warm up the plastic and push all the pieces together. If you dont understand, then search because its a well known repair.
2000 Audi A8L 4.2
1999 Audi A6 Avant 2.8
1998 Audi A4 quattro 1.8T
The crankcase has negligible pressure, and it may even be just slightly negative. The valve cover is super positive pressure. Please excuse my troubles if this is truly a common mode of failure, but none of the information I have found yet actually is for the same system as on my car, or at least the placements are different.... I will try to take note of the system tomorrow during the daylight and see if I can find more relevant information.
Still on the hunt for system diagrams if anyone has them handy... They would surely help me to understand the flow/failure...
Hey, would anyone happen to have diagrams for this cars EGR, EVAP, SAI and or PCV systems. I slept on it and am suspect of all of these systems. I plan to go through the PCV system as a matter of course, but I really want to understand all these systems on this car. Because I'm a backyard mechanic, its just part of my process. I am suspect of EGR/combi valve systems because its mounted right where I get pressure (valve cover).
Ok No EGR on 1.8T. Evap and SAI have no effect on what your dealing with. PCV is where your at, Positive crankcase ventilation system. It keeps a light vacuum in the oil system to evacuate vapors and blow by. There is the PCV valve that meters how much vacuum is put on the system, the big pipe is the oil vapor return, the hose going up to the 3 way Y hose at the valve cover is where its pulling. Then the PCv has its source vacuum from the intake manifold.
I have done dozens and dozens of breather parts replacement on these cars. Yours has nothing special or different than others, its either the earlier style with just 3 pieces, or the newer style with the 4 way pcv and plastic pipes that must be heated and pressed together. Search google, this forum, anywhere its a known 1.8T thing, breather parts fail around 100k
2000 Audi A8L 4.2
1999 Audi A6 Avant 2.8
1998 Audi A4 quattro 1.8T
Yeah, I'm digging in deep at this point. I did remove the combi valve, it was baked with crud slightly open, not responsive to vacuum, but I was able to clean it and it functions with vacuum nicely now. I'm sure its not the only problem, I will work around to the pcv system tomorrow after I get this back on. Thanks for your post. Didn't think this car was special, but just having a hard time finding the exact system on the car to compare.
Since you seem to be very familiar, is it normal for the crankcase and valve cover to be at very different pressures...? I just find it weird...
Hey, the PCV and PRV valves were both completely failed. Spot on there Hoses and check valves seem OK. I finally had some good luck because the car has simpler PCV valve instead of the integrated 4way thing.
... after the parts come I will report back. Thanks for the help towards the right direction here!
I was also getting a P0299 code, turns out it was a cat problem. I had noticed for a while some clunking at engine shutdown. I pressurized the turbo system looking for leaks but could not find any. I finally figured out the cat was loose internally and suspected that could be clogging the system. I replaced it and no more issue. It came off very easy
Just reporting back the PCV and PRV installed and the valve cover seems normal now. Good call
Car is able to get just over 8psi now, still have low boost code. The boost takes a long time to rise, the so the car is pretty sluggish. Also using a lot of fuel. Sometimes brakes feel like the assist is flaking, but the suction jet pump is pretty new and the check valves test ok so far as I can suck/blow. I will probably replace the few left next parts order.
Hey, thanks Craddock. The cat being clogged has occurred to me, but it really did not seem like it was going to be fun taking it off just to check... :/
I wanted to respond with the resolution that actually finally fixed my P0299 code and crap performance in general.
I purchased a cheap replacement cat with the intent to swap it out. We were able to take the three bolts off the turbo from above the car after removing the airbox assembly. Moved the cat back. It was not clogged, and the exhaust side turbine looked really clean.. However the wastegate valve was not seated. It was just flapping around. Checked the actuator, it was actuating well. Outside linkages had tons of slop, even though the nuts all tight on the linkage/rod. The actual linkages all had a lot of slop, particularly where it came into the housing. Loosened the outer actuator rod nut. Then was able to reach with fingers and loosen the inner actuator nut. We metered as close to 5psi into the actuator as possible, seated the wastegate valve nicely at this point, tightened up all nuts by hand, rechecked the actuator was closed well at 5psi, then opening above that, closed under tension at atmopsheric. Locked down. New cat gasket, returned all hoses etc. Reset system. Incredible measurable and driving difference.
Hope this might help someone else in the future. Check that linkage. If it moves all sloppy and you hear the valve in turbo go clackyclack while you slp the linkage... check it out.
attached is a chart before and after wg adjustment. car has 119k, stock.