What does this tube do?

[mohammad]

This is interesting. Forgive my ignorance, but how is this a test of a positive crankcase ventilation valve? Aren't there other ways to test the valve or the ventilation circuit? How about just removing the hose and capping the port at the manifold? (Which makes me think if this may be a case of a cracked intake manifold...)
.

yes the linked thread describes testing it via shaking it and hearing for a rattle and by looking inside the valve at how clean it is. Yes you could also try and remove the hose and cap the valve or port at the manifold for testing. Flooring it would in theory completely open the valve and then when releasing the accelerator if the valve were to stick open may mimic the effects of a vacuum leak and induce the rough idle.

Also, are you suggesting flooring the engine unloaded (I assume you mean with the engine running) and just flooring the accelerator pedal for "a few seconds", making the engine race at it's rev limit? Doesn't that put engine at risk of damage? I've never done this, just wondering if this is a common troubleshooting technique that I'm not aware of. Although it sounds like what I've heard called an Italian Tune-Up...

Ive done this plenty of times (with the cold engine light off) and have not had any issues nor do i have any concerns with the practice, the rev limiter does a great job at protecting the engine.

If there's an air leak at the intake manifold, wouldn't that upset the air-fuel ratio? If that's the case, one could monitor this by watching the A/F ratio using the OBD port as I recall doing this with my phone.

Dependent on whether or not OP has a MAF sensor this may not be very accurate

[nimas1377]

Dependent on whether or not OP has a MAF sensor this may not be very accurate

My car only has the MAP sensor not the MAF


I will take a look at the PCV system but nowadays I'm a bit busy so I will update soon

[nimas1377]

So I checked the pcv today and it was not so free when I shook it but I managed to clean it with carb cleaner and also I found a tube that wasn’t connected to anything so can you please verify if it is like that from factory?



The tube is exactly below the one I asked the question and it’s short and I comes from under it gearbox I assume

[foama]

The picture is far from ideal. I pressume it is the water discharge tube for condensation from the airconditioning.

[nimas1377]

The picture is far from ideal. I pressume it is the water discharge tube for condensation from the airconditioning.

You are right let me show it with more photos


So this is my engine bay and next photo I will go closer to the marked part


And this is the tube I asked in this thread so for next photo I will push it aside and see under it and as you can see it will be a thin tube under just hanging there

I will hold it with my hand in the next photo

[Fummins]

It's a vent hose for the transmission.

[mohammad]

Fummins is correct.

[nimas1377]

So I cleaned my pcv valve but still I have the problem (rough idle some times)
But still I think it might be the pcv valve so How can I 100% test the pcv valve when opened so I can verify if it's causing the problem or not

If needed I have to dig deep to find a replacement but It is an option if it is faulty

[mohammad]

So I cleaned my pcv valve but still I have the problem (rough idle some times)
But still I think it might be the pcv valve so How can I 100% test the pcv valve when opened so I can verify if it's causing the problem or not

If needed I have to dig deep to find a replacement but It is an option if it is faulty

The PCV valve is not unique to the car you can find plenty of tips on how to test the valve on Google and YouTube. In theory with the hose or valve off if you plug the hole in the engine block or cover the valve with a balloon type thing you can test and see if the rough idle occurs. If the problem is fixed them you know it was a PCV valve problem.

[Eggman]

In theory with the hose or valve off if you plug the hole in the engine block or cover the valve with a balloon type thing you can test and see if the rough idle occurs.

Do you mean block the air intake side rather than the engine or valve cover outlet?