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Discussion Starter · #1 ·
1998 Passat AEB. Ever since I bought the car like 3 years ago if I fill the gas tank up completely when I go to start it the first time I would have to kinda hold the gas to keep it running but within about 20 seconds it would be fine and never have to worry about it unless i topped off the tank completely. Well I got some advice on how to fix that and was told to replace the charcoal canister/black box in the rear of the car, I figured they were only 30-40 bucks on ebay ill throw a part at it. Well now every time I go to start the car I have to hold the gas pedal down so it will idle, after 10-20 seconds it will idle perfect and drive great, If I go to restart it then it restarts fine, no issues. I have no codes and this is completely stumping me on what could be wrong. Any help would be greatly appreciated.
 

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Discussion Starter · #2 · (Edited)
Forgot to mention. Gas cap and purge valve about a year old. First things I bought to remedy the situation with no help. I did find a fuel tank breather valve listed for sale on ecstuning.com, any chance this could be the problem? Right now the car is not chipped and I need to go get a smog check for registration, I did pop in a chipped ecu I just got in, couldnt resist to atleast see what it could do for the day and the fuel pump was very loud while running the chipped ecu, when switched back to the stock ecu pump is quiet again.
 

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Coolant temperature sensor, perhaps -- if the engine control unit thinks the engine is hot, it will not sufficiently enrich the mixture on a cold start.
 

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It seems to that it is because of overfilling the tank, you should not add any more fuel after the pump cuts off.
Overfilling damages the charcoal canister, and the purge valve; and can cause flooding which I expect is the reason for the problem.

The fuel pump is either on or off and only runs at one rate, changing the ECU can't alter the noise from the pump.
Maybe the extra noise is from the engine and/or turbo running harder with the chipped ECU.
 
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