[williamoss]

When I fill the tank, my engine runs rough, stalls at a dead stop, sounds like a back fire or sort of stops running starts to run again, stops running starts up again, i.e. very rough driving. Also when at highway speeds the tachometer shows it going down by 100-200 rpm and then up again.  

 

But once I use up some gas say 1/4 to 1/2 of the tank all off this goes away. Any thoughts on this.

 

Oh by the way my mechanic discovered the source of my fuel smell in the cabin which is a vent line which goes across the top of the tank  into the bottom of the charcoal canister. it had a small crack causing the smell.

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[MLB]

Have you had this rough running condition since before the recent gas smell repairs, or does the rough running coincide with any work on the car?

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[williamoss]

started to happen after the vent line was repaired.

 

On the Porsche parts catalog, illustration 201-15 it is item # 8 Part # 944 201 737 01 Vent line.

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[flash]

i think you've found your problem

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[Waylander]

Canister has fallen apart inside, and the breather line will be blocked with charcoal, we had one car over here with the same symptoms and it sucked the fuel tank flat.

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[unknown4u]

There is a small electric valve in the vacuumline to ihe tank n the front enginebay. Between the fusebox and upperstrut you will find it. Inside is diafragma that can be opened and closed with a screwdriver. That little thing regulated the vacuum inside the tank. When open and the tank filled up you can see that the emissionsgastest went wrong. And the engine stumble. After i cleaned that little bastard the emissiontest was better than the car was new sold in 1992. You have to lubricated it and turn slowly the screw. A new valve is about 160 euro or dollar.....

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[williamoss]

My Mechanic ( Marque Motors in Portland) found the problem. Thank you all for suggestions.


 

He replaced the Charcoal Canister # 99320122103 as it was full of gas, (it is located under the drivers side wheel well). He also replaced the following parts located under the carpet in the rear of the car near the fuel filling pipe:


 

The  Purge Valve # 94460524001, Vacuum Valve # 92811042906 and the Shut Off Valve # 928201108302. No more stalling and no more smells of gas in the cabin. As I mentioned above he fixed the vent line that goes along the top of the fuel tank which goes to the charcoal canister.

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