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Discussion Starter · #1 ·
Our check engine light comes on at every gas station fill up for the past 9-10 weeks (about 5-6 fill ups). The cycle goes like this: we fill the car up at a gas station, it has a very rough start at the gas station and barely stumbles to life after a few cranks, the check engine light comes on, when the tank is about 1/3 of a the way full the check engine light goes off, we get gas and the whole cycle starts again.

The first time it happened, I may have not tightened the gas cap enough (my other car only needs one click, and I may not have tightened the Passat's gas cap for the required three clicks).
The VW dealer looked at it about 6 weeks ago and replaced a vacuum line, but the check engine light came back on about three days later (when we got gas).
Could this all be related to air in the fuel system? Wouldn't it clear itself out after 5 or 6 tank fulls? Why does it stumble every time we get gas? I've searched the archives here and at clubb5 and haven't found a situation exactly like mine, so I thought I'd post...
Anyone?
 

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Re: Check engine light every time I get gas?!?? (PhilHVW)

I would check the fuel filter, then air filter, then MAFS.
I had the same problem over 3 months. Turned out to be the MAFS. I hope it isn't that with yours.
 

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Discussion Starter · #4 ·
Re: Check engine light every time I get gas?!?? (Altair 4)

I found a post over at audiworld that might help me...
http://forums.audiworld.com/a4/msgs/151177.phtml
However, I guess it just comes down to picking the right part to replace. I really hoped it was a loose gas cap, or a bad tank of gas (the first time it happened was while travelling, and we stopped at some BP station with really cheap prices).
I have an appointment at an independent mechanic for next Monday.
 

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Re: Check engine light every time I get gas?!?? (Altair 4)

Quote, originally posted by Altair 4 »
No real clue...but I might get a new gas cap. Can't hurt, and can't cost much.

Better yet, start by getting a new gasket for your gas cap ... you may have a breech in your seal.
 

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Re: Check engine light every time I get gas?!?? (chrishart1)

Why is it bad to fill after pump stops first time? I have always filled up more after pump first stops without any probs.
 

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Re: Check engine light every time I get gas?!?? (PhilHVW)

One of the myriad of problems was 5-6 CEL's in 2-3 months. It was determined to be a bad Leak detection pump. This after the dealer accused me of not tightening the gas cap and replacing it . This pump (upon start up) pressurizes the evaporative emissions control system and measures the time for the pressure to leak down. Any leak in the system (loose gas cap) will cause a faster leak down time triggering the CEL. Mine had an internal pinhole leak! No CEL's since!
 

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When I bought my Passat the sales man told me to be careful fueling the car, he said never should you keep putting fuel in once the fuel pump clicks off. If you keep pumping the fuel, to "top it off" there is a sensory in the tank that puts your check engine light on. Try not putting so much in. Once its done fueling, its done. Im from Jersey, we have guys to pump (the law) and one dude keep on filling it to round it to the nearest dollar, messed up my car like yours.
 

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Re: (98passat21)

Quote, originally posted by 98passat21 »
and one dude keep on filling it to round it to the nearest dollar

That's exactly what I do Every time I fill up. Had no idea that it's bad for the car though
 

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Re: (vanyok)

Two years ago I had an incident with my GLX that caused a similar problem. While refueling at an Amoco station, the pump never stopped when the tank filled up resulting in the tank being waaaay overfilled and about 2 gallons on the hot July ground. The genius at the pump's reasoning was,and I quote " Is air in gas tank. I mekanik tventie yeers."
Well after the police came because I refused to pay $28.50 to fill a 16 gallon tank that had over 1/4 tank before pulling in and the pump reads 15.95 gallons pumped
The car was sputtering and stalling for miles to my friends gas station where we siphoned out as much gas as possible - about 2 gallons. I decided to risk driving home from there and calling Roadside from my house. My friend followed me. After about 10-15 miles it cleared up. Apparently the evap canister loaded up with raw gas so it was being sucked through the system into the intake manifold as un-atomized fuel and causing the fun....
 

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Re: (VWGUY4EVER)

I had the exact same thing VWGUY4EVER explained happen while traveling over the 4th of July weekend. I was cleaning the windshield when I smelled gasoline, and looked back to see it pouring down the side of my car like a fountain.
The station's touchless car wash got the gas off my car, but the bucking and stalling persisted for a few miles, then went away for good.
Just goes to show you shouldn't trust an auto-shutoff lever on a gas pump you don't know.
 

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Re: Check engine light every time I get gas?!?? (VdubTX)

Quote, originally posted by VdubTX »
Why is it bad to fill after pump stops first time? I have always filled up more after pump first stops without any probs.

It's bad for your car, and it's bad for the environment. There needs to be room in tank of your car for the fuel to expand and for the system to deal with excess vapors. If the tank is excessively full the car's vapor recovery system can not cope, or will become clogged with fuel.
Details I was able to find in a brief web search:
http://www.cleanairwisconsin.org/indivactions.pdf
http://www.chicagotribune.com/...olumn
http://www.time.com/time/natio...n=yes
http://www.stretcher.com/stories/990823m.cfm
http://www.weights.az.gov/Cons....html
http://yosemite.epa.gov/r3/pre...ument
http://www.dnr.state.oh.us/wat....html
 

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Discussion Starter · #14 ·
Re: Check engine light every time I get gas?!?? (PhilHVW)

Just a follow up on my CEL problem. I told our independent mechanic to replace the EVAP purge valve and after three fill ups and nearly two weeks it seems to have cured the problem.
From reading more posts over at audiworld, this seems to be a common problem on both the 1.8T and the V6 2.8 with these symptoms.
 
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