Another cause of lumpy and rough running.

[Timo. 0]

Dont know whether any of you guys/girls know about this. Maybe some of you do! I was reading some technical data on the VR6 engine and found this about the carbon cannister -

 

"The Carbon Canister Frequency Valve (N80) begins to operate after

oxygen sensor operation has begun.

Valve operation is load- and speed-dependent during driving operation.

The valve is completely open at full throttle and completely closed

during deceleration fuel shut-off.

 

• Substitute function: *

If power to the valve is interrupted, the valve remains completely open.

This could lead to rough running at idle speed and during partial load

acceleration."

 

N.B. The substitute function.

 

Sounds like another good excuse to get rid of the old CC.

 

Just thought this might be of interest.

 

cheers

 

timo

[dr_mat 0]

This will show up on VAG-COM though, so you'd know about it if it wasn't working..

[Kevin Bacon 5]

The engine runs better with the CC connected mate, I've tried it!

 

You can test the frequency valve though. Disconnect the hosing from it and plug the one that goes to the throttle body (black hose that passes over the PCV breather valve), start the car from cold. The valve will be closed. After about 2 minutes, the lambda probe kicks in and you should hear the valve pulsing, which is where it gets it's name 'frequency valve' from. That's the ECU telling the valve how much de-hydrocarbon'd vapour to let escape into the engine. The pulsing varies with engine speed and when the throttle is on overrun, the valve should be locked shut.

 

If the valve is always open, it's either knackered or the wiring to it is but as Matt says, N80 is monitored by the ECU and will code it if it dies.

 

K

[Timo. 0]

Its more for the people that dont have VAG COM (like me) and who dont want to shell out money to find out what the problem is without doing a few tests on the usual suspects 8)

 

timo