# Failed emission test - weird gass tank problem



## turboprick (May 12, 2004)

I live in Illinois where by law cars newer than 1996 get emission tested only by OBD (on-board diagnostic, or something like it). So, I failed the test, showing the following codes: 

P0450 - EVAP Control System Pressure Sensor 
P1446 - Manufacturer Specific Code 

Last year the law did not require "computer only" test, and I passed the test without a problem. I read the warning codes back then, and they were the same, so I new the emission was OK, it was something else. 

Here things get really weird - at the same time my "check engine" lite initially went off - this was after a minor repair at the local dealership - my gas tank started acting up. I could not, and I still can't fill gas normally, it has to be done vary slowly, otherwise the neck overfills and shuts the pump. 

The dealer came up with some ridiculous and outrageous explanations having to do with the catalytic converter, the gass pump and other things, well over one grand to fix, so I dismissed them right away. 

I think it's got to be something related to the EVAP unit, or the sensor that measures pressure in the tank. It is fooled into thinking that the gass cap is off, so it shuts some valve, or something. Also noticed that after I drive for awhile, it builds up pressure in the tank, and when I shut the engine down, it makes some droning sound for a few minutes, unless I unscrew the cap, then it stops. 

I would have replaced the EVAP unit, but I'm not sure that will take care of the computer reading. 

Has anyone had such a problem? Or knows how to go about fixing it? 


Thanks


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## wes (Apr 30, 2002)

turboprick said:


> I live in Illinois where by law cars newer than 1996 get emission tested only by OBD (on-board diagnostic, or something like it). So, I failed the test, showing the following codes:
> 
> P0450 - EVAP Control System Pressure Sensor
> P1446 - Manufacturer Specific Code
> ...


 Do you have a check engine light? If so was it related to the EVAP code? If so then I would check all the hoses to and from the cannister and if they check out OK then follow the FSM for vacuum and pressure testing the cannister itself since it plays a role.


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## Ninety-Nine SE-L (May 5, 2002)

Have you tried getting a new gas cap? It may sound weird, but a gas cap alone can solve many problems.


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## 98Midnight (Apr 23, 2004)

Let's see. I'm looking into my crystal ball!!!

I'll bet you anything it's the vent control valve. I just went through this exact experience about a month ago with my B14 (symptoms and fault codes included). For about $100 at the $tealership for the new part and 10 minutes of your time the problem will disappear. :cheers:

BTW turboprick gas is spelled with one "S" (gas) not two (gass).


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## turboprick (May 12, 2004)

*Vent control valve*

Thanks 98Midnight, 

The vent control valve sounds a pretty plausible suspect. My problem with the "check engine" light began after the car was in a body shop for some front end work. Somehow they managed to screw it up, but I couldn't prove it to them. 

Do you think it might be a disconnected sensor, or however the control valve is connected to the OBD, maybe the computer just reads the gas tank pressure? What was it in your case? 




98Midnight said:


> Let's see. I'm looking into my crystal ball!!!
> 
> I'll bet you anything it's the vent control valve. I just went through this exact experience about a month ago with my B14 (symptoms and fault codes included). For about $100 at the $tealership for the new part and 10 minutes of your time the problem will disappear. :cheers:
> 
> BTW turboprick gas is spelled with one "S" (gas) not two (gass).


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## 98Midnight (Apr 23, 2004)

Well for starters, you VCV is attached to the forward side of the charcoal canister. It's located behind the driver's rear wheel. It has one connector, one line connected to it and two 10mm bolts mounting it to the canister. If you look under there and see that the everything is connected, I would guess that your VCV is not operating properly. After all, it's a valve located in a place subjected to dirt and corrosion so it could simply be stuck or hanging up.

In my case the OBDII scanner was reading a fault that is typically generated by the vent control valve.


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