1992 K10 Micra 1.2 Vac hose plug?

[Chris Smith]

Sorry, I think I put this on the k11 General Discussion by mistake. Should have been on here.

My K10 Micra was running a bit lumpy, nothing terrible but a bit jerky on acceleration, very annoying. So I went looking for a cure.

I read somewhere that if you partially block the vac hose with a rubber bung that has a 1mm hole in it - running and acceleration immediately improve. So I tried it.

And it is correct, no more lumpiness, car pulls quicker and more smoothly.

How can this be true?

 

[Chris Smith]

I am talking about the crankcase ventilation system. The hose that emerges into the air filter housing which is roughly 10mm in diameter. I have plugged it with a solid nylon plug with a 1mm hole drilled through the centre.

Anybody shed any light on why this works?

 

[frank]

any manifold vacuum leak will cause the car to run lean, so your restriction is richening the mixture slightly chris
slightly rich will give you more power but less mpg

 

[Chris Smith]

Thanks for your reply, I'm sure you are right. But since there is no leak anywhere in the vacuum hose between the crankcase and the air filter, I think the engine was already running a bit lean. Fitting the plug appears to have restored a sensible balance.

 

[frank]

There is no manifold vacuum in the filter case tho

 

[Chris Smith]

Perhaps the hose I am talking about isn't a vacuum hose as I was told.

Is it a hose that brings warm air up from around the exhaust manifold? Which is meant to make running better in winter by supplying warmed air to the engine?

If it is, how do I shut it off in hot weather - other than by plugging it?

 

[frank]

thats to stop the carb icing up, there should be a flap here

 

[Chris Smith]

My other K10 - which is an earlier model - has the lever ringed in your picture. But my 1992 model has a device on the side of the air filter casing with the part number 1650 19B00 stamped onto it. It has no Winter/Summer lever incorporated into it, so I assume it must work by measuring the temperature of the air and adjusting the flow of warm air entering the air filter accordingly. Maybe it has stopped working or has jammed open - letting too much warm air to enter the air filter - even in warm weather.