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[mrjimbo]

What would the symptoms of a faulty purge valve or carbon canister be?

Rough idle ?
Missfire ?
Poor mpg ?
Any other symptoms ?

[Kevin Wood]

It doesn't do a whole lot as far as engine running is concerned so I doubt it would be that noticeable. Might get a rough idle occasionally perhaps, and if the system was permanently blocked the fuel tank might pressurise or build up a vacuum.

Kevin

[mrjimbo]

It doesn't do a whole lot as far as engine running is concerned so I doubt it would be that noticeable. Might get a rough idle occasionally perhaps, and if the system was permanently blocked the fuel tank might pressurise or build up a vacuum.

Kevin

Cheers Kevin,Thats what i thought, it was just a suggestion from one of the vehicle technicians at work as a possible cause of the poor mpg issue i'm having with my car at the moment. He wondered if the one way valves in the purge system were sticking.

There's no smell of fuel or any sign of vacum leaks.

[2woody]

symptoms are....

runs like a dog
very rough idle
sky-high emissions
probably excessive fuel consumption.

iif the valve is stuck open or the hose is split, then the engine is ingesting extra air, for which it tries to compensate, but can't.

[mrjimbo]

Is there an easy way to check the Purge valve then ?

[2woody]

pull hose off plenum chamber top ( the smallest of the four )

engine off - should be able to blow through it
ignition on - shouldn't
engine running - shouldn't

[mrjimbo]

OK i'll give it a try when i get 5 minutes 

[mrjimbo]

Just taken the pipe off the back of the plenum to check the purge valve, unable to blow through at all. Makes no differance whether the engine is running or  not, can't even blow through it with the ignition off.

Tried sucking on the pipe and it's the same, no flow through the valve whether the engine is running or not or with the ignition off.

What do reckon  2woody ?  Fubar'd purge valve ?
It's not running rough or idling rough, just using more fuel than i think it should.

[2woody]

valve, evap loss canister or pipework to tank. Need to check for blockages.

having said that, a complete blockage wouldn't cause the poor fuel economy

have you checked the lambdas out ?

I'm having similar problems with a car of mine at the moment - it refuses to get emissions down to MOT levels.

the bust hose had a large effect, but I've found that the lambdas are giving widely different outputs, with the injection trying to compensate by richening the mixture. try looking at the lambda outputs if you can get access to a reader.