krzysztofkow

Hey guys. I appreciate any feedback on my issue. Here it goes....

Car: 2005 A4 1.8t, manual, 125K miles

Problem:
- steady check eng light
- super high vibration at idle (the whole car shakes), engine struggles to stay alive at idle
- at higher speeds vibration less noticeable but eng still lethargic
- no vag-com, so v-checker codes:
P1136 - long term fuel trim add bank 1 sys too lean
P0171 - fuel trim bank 1 system too lean
P1111 - oxygen sensor bank 1 system too lean
P1128 - long term bank 1 sys too lean
P0507 - idle control system higher than expected
P0456 - evap sys small leak detected
P0300 - multi cylinder misfire detected
P0301, P0302, P0303, P0304 - cylinder1,2,3,4, misfire detected

MY troubleshooting:
- gas cap ok and fuel pump sounds ok when turning the key
- visually inspected vacuum lines & check valves, nothing obvious
- disconnected the plug from the MAF sensor, no change in the way car is running
- removed MAF sensor, evidence of oil on both sides/screens

Could it be the MAF sensor? I expected the eng to die or go to some default/safety mode when connector was removed. Any advice will help. I am lost and the car is stuck..

turbo510

Those symptoms sound like an air leak downstream of the throttle, so I wouldn't expect to blame the MAF sensor. Anything that connects to the intake manifold should be inspected, and maybe pinch hoses with pliers one at at time, looking for one that slows the idle when pinched off. If nothing, then spray around the intake manifold gasket(s) with starter fluid, propane, etc, looking for a change.

krzysztofkow

Thank you turbo510 for your advice. When I was initially checking vacuum lines, it was getting dark and drizzling. I had better weather and more time yesterday. Did a lot more research, including this thread:
https://www.audizine.com/forum/showt...on+vacuum+leak
Followed the "pinch test" of the vacuum lines entering the intake manifold. Idle leveled off when pinching the line going to the pcv valve. Turns out the check valve in the pcv valve was blown and the crankcase breather tube/elbow under the intake manifold was broken. All taken apart and awaiting parts. Picture shows what I basically needed. Thank you for your help.
https://c1552172.ssl.cf0.rackcdn.com/397798_x600.jpg