Problem with engine vaccum (blue top)

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Qantum
Posts: 6
Joined: Wed Dec 20, 2017 2:52 pm

Problem with engine vaccum (blue top)

Post by Qantum »

Hi
I have problem with my engine. Car works with very high RPM (2000 up).
English isn't my native language so i have video where you can see my problem.
I replaced each tube I found, but I still have a problem.

htt ps://youtu.be/4AycjHir5pI (Delete space)
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Lauren
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Re: Problem with engine vaccum (blue top)

Post by Lauren »

Here's your link so it works:

youtu.be/4AycjHir5pI
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jimi
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Re: Problem with engine vaccum (blue top)

Post by jimi »

That pipe you connected/removed at the end of the video is for the MAP sensor and must remain connected, the engine won't run/idle properly with it disconnected.
With it connected run the engine until it's up to temperature may take a good 15/20 minutes.
Does the RPM drop gradually as the engine warms up to around somewhere 800/1000rpm ? if does then that's perfectly normal for a MK1.

If the RPM does not drop then it's probably your AAV sticking so read on.

The AAV (Auxiliary Air Valve) is basically an air valve that is controlled by coolant temperature. When the engine is cold it's open and allows air past the throttle butterfly, the MAP sensor tells the ECU about the drop in manifold pressure (more air) and the ECU alters the fuelling to suit causing the rpm to increase, which is why the MK1 can idle at 2/2.5k rpm when cold. As the coolant heats up the valve closes, reducing the air, ECU compensates, idle drops. The warm idle is set by an air screw on the top of the throttle body (normally hidden under a round black plastic plug)
They are well known for sticking and causing problems.
There's an easy check to carry out to find out if the AAV is functioning properly.
With the engine at normal running temperature, take the inlet pipe off the throttle body, if you look at about the 5 o'clock position you will see a small hole (about 5mm dia ) block off the hole with your finger (press tightly) and see what happens, if the AAV is open then the rpm will drop, engine may even stall.
The hole you want to block is marked C in this picture. (picture courtesy of Paul Woods)
Image
More info on the AAV and solutions here
http://www.mr2oc.co.uk/know-your-2-know ... kbartid=54
http://www.mr2oc.co.uk/know-your-2-know ... kbartid=55
http://www.mr2oc.co.uk/know-your-2-know ... kbartid=56
ufer
Posts: 32
Joined: Wed Dec 22, 2010 9:54 am
Location: Bourgas, Bulgaria

RPM

Post by ufer »

I made that trick 3 years ago - (2500 rpm). At first with 5 mm hole (1800 rpm) and second - with 4 mm hole (1500 rpm) because in my country (Bulgaria) is warmer as in the UK. These RPM now are absolutely perfect for our climate. I gave this trick to some friends of mine and they were fully satisfied too.
Qantum
Posts: 6
Joined: Wed Dec 20, 2017 2:52 pm

Re: Problem with engine vaccum (blue top)

Post by Qantum »

Sorry for not responding for so long but to be honest i forgot :)
Car after ingintion adjustment and burnout now works good I think.
When cold rpm rise to 2500 but when becoming warm rpm falling to ~900.


Still some work to do but almost finished :)
imgur.com/a/pX4qPls

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