EVAP solenoid valve-What does it do?

[Corvr6 0]

Mine has a regular clicking sound and you can feel it vibrating when it clicks, I'm sure it never used to.

It is shown in the manual,but not really explained at all. :?

It is located under the MAF connector, I would suggest it links the carbon canister to the intake manifold.

 

I am changing it, anyone else had to?

 

Is it possible for a faulty valve to cause an irregular missfire?

 

I have checked or replaced,

 

New plugs (During head rebuild-Stealth)

New Ignition leads(Magnecor 8mm,used metal tool to install)

Checked Coil pack(Used water spray test at night,no visible cracks either)

Checked Temperature coolant sensor(steady reduction in resistance as temp rises)

EDIT

I don't think the engine was up to operating temp when the following 2 tests were carried out,see new post below. :oops:

Checked Oxygen sensor(less than 100mv @ idle,approx 700mv@3500)

Checked MAF(Wouldn't start when disconnected)

EDIT

Reset ECU(Disconnect battery for +15 mins)

 

Any other suggestions appreciated before I take it to local specialist to get the errors (if any)downloaded.

[Kevin Bacon 5]

That valve just allows the fumes from the carbon canister to be drawn into the engine. The ECU switches it to open when the car is off idle. It is switched to closed when idling.

 

The valve is crap on the Corrado, I use a black one from a Golf VR6 instead as they are a lot more robust.

 

The blue corrado ones have a weak valve and stick open, giving a fuel whiff and yes it will affect the idle if jammed open.

 

Part nos -

Valve - 0 280 142 300 or 058 138 517

Rubber shroud - 051 133 459 A

 

Kev

[Corvr6 0]

Thanks for the quick reply and part no's.

 

Which part no refers to which valve?

[Kevin Bacon 5]

Sorry, scrap the Golf valve advice. Replace the Corrado blue one, part no - 034 133 517

 

The Golf one I used is from an OBD2 car and works differently.

 

To test yours, plug the black hose that leads to the throttle body, pull the valve off it's mount and leave connected but pull it up from under the air inlet pipe so you can hear it.

 

With the engine running, blow into the smaller bore tube. You should not be able to blow through it. CC fumes aren't inhaled when the engine is cold.

 

After a few minutes, you should hear the valve pulsing as the engine starts warming up.

 

If both conditions above are true, you don't need to replace the valve.

 

Kev

[Corvr6 0]

Right,thanks for the clarification. :)

 

I have yet to carry out your suggestions,it is quiet when cold and pulses when warm.

 

I have been running some other tests today instead and I think I have fallen prey to the Mad As F**k sensor :mad: which is more probably the cause for the missfire.

Once up to operating temp (+80'C) I can pull the MAF connector and she carries on idling after a tiny increase in revs,but doesn't cut out.

 

With the MAF connector replaced, the O2 Sensor reads 600-900 mv when idling,and 900 mv at any other rev range.

If allowed to idle again the voltage starts to drop only fractionaly,eg,after 10 seconds of idle voltage would still be +850 mv.

 

If I disconnect the O2 connector and the MAF the voltage drops very quickly to less than 100 mv from 900mv in about 15 seconds and the engine is trying to stall,so I reconnect the MAF and the revs come back up at the same speed along with the voltage.

 

Does this suggest the MAF is faulty,I presume that the O2 sensor is doing what it should? :?:

 

 

 

I have pulled this info on the EVAP valve from this post

 

http://the-corrado.net/.archive/forum/viewtopic.php?t=520

 

 

Carbon Canister Frequency Valve (N80)

 

The ECU determines the duty cycle of the frequency valve to regulate the flow of fuel vapours from the carbon canister to the engine. When no current is supplied to the valve, it remains in the open position. The valve is closed (duty cycle 100%) when the cold engine is started.

 

Triggering

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.

 

Self-diagnosis

The ECU recognizes open circuits and short circuits in the component.