gpgyo

Many months ago as I was coming to a stop the RPMs dropped dramatically and I thought the car was going to die. It didn't happen every time or even frequently so I didn't think much of it. Eventually it got to the point where it idled quite rough when the car was in gear and I was stopped. The CEL finally came on and the auto parts store pulled two codes: PO 441 and PO 171. Along the way I developed the problem with difficulty restarting after fueling.

Here's what I have:
- 2006 A4 Quattro, 2.0T, tiptronic
- 76K miles
- Dakar Beige

Here's everything I've done (in order) in the last 1,300 miles:
- Replace PCV valve with BSH PCV Bulletproof replacement
- Changed oil/filter
- Changed air filter
- Cleaned the MAF
- Cleaned the IAT
- Cleaned the throttle body
- Replaced the valve cover gasket
- Replaced all coil packs and plugs
- Replaced the purge valve (N80)

Initially I thought it was the PCV valve so that's why I started there. When I took the OEM PCV off I saw it was a later revision so I checked my service records and found where the dealer had replaced it a while ago so I don't think I got anything out of that. It was due for oil and air filter so I didn't change those thinking either would help.

I read a lot of posts about the benefits of cleaning the MAF, IAT, and throttle body so I did that next. When none of that helped I pulled the plugs to see what condition they were in and found them in an oil bath. That led to the valve cover gasket change and I figured I might as wells change the coils packs while I was at it. After the putting in the new plugs and packs I took it to the gas station on a test drive and had the hardest time restarting it. Most of my searching on hard restarts after fueling pointed at the purge valve so I replaced that. This was likely my biggest problem all along. After changing it, the car started running and idling pretty good and 50 miles later the CEL went out.

I still have a small shudder when I come to a stop. It happens just before I stop and only lasts a second. Its not pronounced but its there. Any ideas what might be causing it. At this point I've read every thread on every forum that sounds remotely similar and I'm out of ideas.

Thanks.

vannyhuj

Here's what Ross-tech wiki says. Based on what you have done already, it is looking like either the N115 (charcoal canister) or an air leak in the system.


16825/P0441/001089 - EVAP Emission Control Sys: Incorrect Flow

Possible Symptoms
Malfunction Indicator Light (MIL) active
Possible Causes
Evaporative Emission (EVAP) Canister Purge Regulator Valve (N80) faulty/jammed
Evaporative Emission (EVAP) Canister Purge Solenoid Valve (N115) faulty/jammed
Evaporative Emission (EVAP) Canister Sealing faulty
Pipes between Tank Breathing and Throttle Body leaky/blocked
Possible Solutions
Check Evaporative Emission (EVAP) Canister Purge Regulator Valve (N80)
Perform Output Test
Check Evaporative Emission (EVAP) Canister Purge Solenoid Valve (N115)
Check Evaporative Emission (EVAP) Canister
Perform Basic Setting
Check Pipes between Tank Breathing and Throttle Body

16555/P0171/000369 - Fuel Trim; Bank 1: System Too Lean

Possible Causes
Mass Air Flow Sensor (G70) defective
Intake System Leak(s)
Possible Solutions
Check Mass Air Flow Sensor (G70)
Check Fuel Pressure Regulation
Check Fuel Pump
Check Injectors
Check Intake System for Leaks
Check Exhaust System for Leaks
Check Secondary Air System for Leaks
Check Vacuum Pipes for Leaks

gpgyo

Thanks for the tips. I'll check what you suggested next.

By the way, yesterday was the first time I've filled up since I replace the N80 and no problems restarting after!