What have I missed?

[mikees501]

2003 A4 (B6) 1.8T TIP 130k Quattro wagon AMB I rarely have to post on this forum since so many have posted before me. I’m trying to bring back a neglected ’03 wagon and I also own a 01 A4 with 220k on it that runs like a dream. I purchased it with 75k miles and have done all maintenance since. This 03 has been challenging and what I can’t seem to fix is a rough idle and positive air pressure at valve cover (oil cap rattles pretty hard if you loosen it) I do own a Bentley manual & VAG I’ve replaced the timing belt, water pump, tensioners, serpentine, thermostat, etc. Completely went through the vac system with a fine tooth comb. All lines are clean and no leaks. I replaced the spark plugs, MAF, fuel filter, DV, PCV, PRV and CTS Insalled known good coil packs from the ‘01 Fuel rail was a mess and most wires had cooked and cracked. Fixed that. 02 sensors checked out fine on VAG I cleaned the TB and did adaptation. Leak-down and compression checks were great. No CEL’s I’ve done nothing with the “N” valves What have I missed?

[Prospeeder]

Well there should be a breather valve that regulates crankcase breathing. Ignore the first picture
http://forums.audiworld.com/showthread.php?t=2772713

Could have a collapsed or clogged breather hose, if the thermostat was stuck open in the past for a long time, alot of sludge and moisture builds up in the plumbing from the engine never reaching temperature.

[mikees501]

Originally Posted by Prospeeder

Well there should be a breather valve that regulates crankcase breathing. Ignore the first picture
http://forums.audiworld.com/showthread.php?t=2772713

Could have a collapsed or clogged breather hose, if the thermostat was stuck open in the past for a long time, alot of sludge and moisture builds up in the plumbing from the engine never reaching temperature.

Thanks for the reply Prospeeder,
I've already replaced all of that stuff as part of the rebuild.
I rebuilt an 01 A4 that now has 210k miles on it and it has had no problems. This 03 has been a pain.

Thanks for responding.