Fuel Vapour valve - Carbon canistor valve if you prefer

Level 5 User Joined: 19 Sep 2004 Posts: 115

What would cause the said valve to open when the car is at idle? or is it supposed to do that. (I thought it was only supposed to open under load)

Mr Quoter-vator Joined: 16 Feb 2004 Posts: 7405

wel at idle it should be shut...either it is stuck open, or it is getting faulty readings from the ECU telling it to open when it shouldnt be.

how do u know it is open?

Level 5 User Joined: 19 Sep 2004 Posts: 115

Iratic idle. If the pipe gets blocked it settles down.

Spammer Joined: 27 Jul 2004 Posts: 5717

are you on about this carbon canister thing under the right hand side headlight ????

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

it opens at all sorts of time. to make sure the ECU doesn't have dody software start the car from cold, revs the engine up and down whilst touching the solenoid, when cold it should not operate, if it does then theres a proble with the ECU. It only operates when up to temp.

Check the piping for splits etc

Level 5 User Joined: 19 Sep 2004 Posts: 115

It does it when its warm. Pipes arent split as i can block the pipe at the Fuel filler pipe end and that cures it.

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

well it must be split/leaking then if blocking it solves the problem.

I would say check the emmisions but you won't have the facilities to do that.

Level 5 User Joined: 19 Sep 2004 Posts: 115

How can the pipes be split if i am blocking the end off at the extreme end of the pipe by the fuel filler neck. I just always thought the valve should not open unelss the engine is under part load. If it open's at idle wont the extra fuel vapour trigger the lambda to reduce the fuel injected.

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

Becuase theres 2 pipes at the fuel filler end and the other may be sucking in air.

The valve opens under an array of operating condictions. Its purged of the vapours by engine vacuum so at full throttle theres no use for it as such as theres little manifold vacuum. However at idle, part throttle and over run condictions theres vacuum so its activated.

Also a dodgy fuel cap can cause the problems you mention, it will draw fresh air in from the outside causing it to lean out.

You put far to much faith in the lambda sensor as well my good man. Lambda sesnors are not terribly fast reacting or accurate and pinhole leaks in the exhaust can affect the lambdas reading.

Level 5 User Joined: 19 Sep 2004 Posts: 115

It dont help me having a 2 inch crack in the manifold then. He He He. That will be resolved this weekend as i managed to get the broken stud out of the replacement one last night.

Level 5 User Joined: 19 Sep 2004 Posts: 115

Actually thinking about it the ruff ridle sounded very much like your White chammy

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

pah that thing, feck knows whats wrong with it.

But when the car was on the road Mark said it never ran right again so theres something fundamentally wrong, I cannae be arsed going into an exhaustive search for what it is though!

I am actually doing a tech article on EFI fault finding, its turning into quite a book though!

Level 5 User Joined: 19 Sep 2004 Posts: 115

Well i have just been reading through the dialogy's. Found a few snippits.
Found one section in bold text saying an oxygen sensor fault will cause the valve to open under no load. Also the valve openeing during idle can cause irratic idleing and stalling.

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

unplug the lambda sensor then, see what happens. But like I said if theres a leak pre lambda then it will not be doing its job, this could also tie in with the fact the valves open as a leak pre lambda will make it appear lean so open the valve.

Level 5 User Joined: 19 Sep 2004 Posts: 115

Wont an unplugged lambda just return a constant lean. As i thought lambda sensor generated a small oscillating voltage and thats what the ECU looks for. So if the lambda is unpluged = no voltage = ECU thinks constant lean.

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

Thats a point, some just use a cold start map others may just leave the solenoid valve on constantly to enrichen the mix.

The lambda does look for a voltage but like you say it oscilates so it actually only takes the mean value of it. If you had an occiliscope you could see it.

Anyway easy way to see is run the engine up to temp then spray carb cleaner on the crack, if the idle sorts itself out theres your problem for sure.

Exhaust leaks are an arse especially on new cars with twin lambdas, you wouldn't beleive the trouble a section of porous weld on the lambda boss creates!

Level 5 User Joined: 19 Sep 2004 Posts: 115

Could this also be the problem with the ya chammy.......

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

lambdas fecked on the chammy and the exhaust is leaking but its not the problem.

With it unplugged its still crap with the ICV unplugged it no longer hunts, with the TPS unplugged as well the revs raise but its smooth.

Its ok aside from the hunting idle which doesn;lt happen all the time. The problem is light throttle application, boot it its fine, very gentle rev its ok, but rev for normal drive it either cuts out or stumbles.

However over 2krpm the throttles fine at any position.

Although the cars not happy pulling a load.

The car has something very wrong with it as it came back from the head change that the previous owner gotr acting like this.