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iauto8, ASE Certified Technician
Category: Car
Satisfied Customers: 137
Experience:  15 year ASE Auto Technician. European import specialist.
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I Have an Audi -A4-2.0T Year 2008 |One Month Ago I have

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I Have an Audi -A4-2.0T Year 2008


One Month Ago I have a message in the dashboard " CLOSE FUEL CAP" I stopped and I re-closed ,But still showing up the same message.


After driving for 1 hour the engine light show up , I put my scanner and I have the following codes P0455/P0456.


I Checked my car for gas smell or leaking beginning with the fuel tank , then underneath of rear seat and in the trunk, I removed the gas cap and re-installed .


 I checked the evap leak detection pump and fuel pump control module and I removed the underneath cover to follow the hoses until I got to the purge valve solenoid .


I Replaced the canister purge valve selenoid located at the left rear part of the intake manifold and the engine light disappear , After 45 days the engine light show up again with the same codes and some time these codes " system to rich  bank 1 and system too lean bank 1".


 I have been noticing  when the gas gauge white indicator is in the first line the"CLOSE FUEL CAP" appear , yesterday my car was empty of gas and I filled up ,when i try to started its hesitate like 3 times and finally start ..another thing that i noticed is sometime is lacking of power in the first 20 second and then the force/torque/power is back.


The codes system too lean and system too rich, i know that i should replace the oxigen sensors , but i dont think these will solve the problem ...


Some time I have been adding fuel enhancer/ fuel injector cleaners to my car , can this cause some kind of problem and the sensor are sensing foreign liquid in the gas tank ?

iauto8 :

From every thing you describe I would say the purge valve is bad again. When they fail they stick open a bit. This causes the engine to gulp some raw fuel when starting the car right after fuel fillup. This can cause a rich code and also the large leak code. Once the fuel level is lower it will act as a vacuum leak, causing the lean code. When you replaced the valve did there appear to be anything stuck in it? I have seen charcoal canisters come apart and small pieces of charcoal can get stuck in the valve holding it open. This is not common on this car though. My advise would be to try another one. Just check and make sure nothing is getting stuck in the valve. Chris......


The purge valve that i am talking about is this

Full Size Image



when i changed nothing was stuck


what happens if i replace again and still doing the same thing , what about the hesitation in the first seconds of driving



are you there

iauto8 :

That is the correct valve. To see if anything is getting in them I usually tap them a few times on the vacuum port on a white piece of paper. Look for gray or black dust to come out. The hesitation when first started could be caused by this valve leaking. It is like starting your car with a vacuum hose disconnected. After a few seconds the computer takes over fuel management and is able to correct the lean condition. If you replace and it happens again the evap system should be checked for leaks with a smoke machine. I will post test procedures for the purge valve as well. Chris......

iauto8 :


Tests: Test the N80 Canister Control Valve (CCV) function as follows:

1. Cool the valve in a freezer and then manually energize it by applying power and ground to the valve.

2. Make sure that the valve opens and closes fully and does not stick. Repeat the test with the valve heated to underhood operating temperature.

3. The valve must open and close fully and never stick.

4. Check the vacuum and vapor lines, from the N80 valve to the canister, for leakage or damage.

Test the Leak Detection Pump (LDP) function as follows:

1. At the LDP, disconnect the electrical connector.

2. Apply B+ to terminal 3 of the LDP (terminal 3 is where the Green/Yellow (GN/GE) wire would connect).

3. Apply ground to terminal 2 of the LDP (terminal 2 is where the Grey/Red (GR/RO) wire would connect).

4. Apply vacuum to a small line vacuum nipple (this should hold vacuum).

5. The purge filter should now be sealed off.


great , i will do this , thanks a lot .

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