Discovered one way valve on line from intake to charcoal canister was broken? Effect - LotusTalk - The Lotus Cars Community
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post #1 of 4 (permalink) Old 03-17-2019, 12:00 PM Thread Starter
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Discovered one way valve on line from intake to charcoal canister was broken? Effect

While installing the ABS delete kit I discovered the one way vacuum valve on the line from the intake manifold to the charcoal canister was broken in half and the line was open to the atmosphere.

Does that mean I had an open vacuum leak and once fixed the idle will be very low? Or does the idle air control valve have the scope to adjust for a major leak like that?

I wont be able to start her up for several more weeks so I am curious what to expect.

Also is the little valve a special part from lotus or can I get that valve any where?


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post #2 of 4 (permalink) Old 03-18-2019, 07:44 AM
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Not sure on your car but there is usually a restrictor or small fitting so any potential leak in the Evap system would have a minimal effect on the motor. Depending on where the fitting is will determine the effect on the motor. If it is before the idle motor it would not have any effect on the motor's speed but could affect the A/F ratio and that could the idle quality and speed. If any adjustments were made with that fitting broken you would have to readjust after fixing it to get it right again.
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post #3 of 4 (permalink) Old 03-18-2019, 08:20 AM Thread Starter
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Thanks Dave

Good point - I am trying to think if its before or after the "butterflies"

The port is pretty close to the head so I would think the location is after the butterfly which would cause idle problems, if not just a little unfiltered air getting in.

I will get some pics and report back with more details from the vac diagram. Surely this has or will come up. That little anti reversion valve is very fragile plastic in a tough environment.

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post #4 of 4 (permalink) Old 03-18-2019, 03:43 PM
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The Charcoal purge feeds into one of several rails on the intake manifold. If it is open to atmosphere, it may raise idle, but probably won't cause cause MAP sensor problems (MAP should be 1/2 Baro at idle). Will probably cause the IAC to compensate, though it will may not be able to... Which could cause stumble or stalling off idle. It could lower the pressure in the intake manifold rail shared with the fuel pressure regulator, so it could prevent the fuel pressure regulator from being able to increase fuel pressure with boost... which would be bad.
And if open to atmosphere, you should definitely be able to hear a whiny high pitched nose of the intake valves.

The valve can also fail in a way where it isn't open to atmosphere, but it is open internally, and no longer a check valve. This could cause boost pressure to go into the charcoal canister...

Replace the hose and check valve anyways!

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