Fiat 500 1.2 lounge - had the car for a couple of years but due to our low mileage I've just got to change the spark plugs. When the air box was removed it exposed the pipe (see photograph) that has been blanked off with a bolt.
Although the car has run fine in this condition and for the moment I've left it alone could somebody clarify:-
1:- What is the pipe and its function?
2:-Why would you blank it off?
3:- The place it should connect to - under the air box is open to atmosphere - is that OK?

As I've said its running OK and has for the last 2 years

Suggest it's a breather pipe from crankcase to airbox.
Goudrons will know better than me why it's been blanked. He'll no doubt see this and comment. Strange.
But if it is, I'd carefully check the condition of your oil and get the engine flushed out before changing oil and filter - and get the pipe back into use.

Looks like the throttle bypass. It allows air to bypass the throttle when closed so the engine will tick over smoothly. with this blocked the ecu has to open the throttle slightly to allow the car to tick over. it should connect to a small spigot on the back of that air filter box.

Is the part of the airbox that it connects to still there?

Maybe when they changed the plugs it snapped off because they didn't disconnect the pipe and rather that replace or mend it they just blocked it off to stop stuff going all over the engine bay?

Vac pipe?

Thanks for the replies, I was waiting to see if there was other suggestions.
Next weekend I'll check to see if the spigot is still there as suggested by Cyberface. Apart from a broken spigot is there any reason to blank it off?

Thanks all for taking the time to reply , will let you know next weekend regarding the spigot.

Jernas said:

Apart from a broken spigot is there any reason to blank it off?

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In a word, no. If it didn't serve a function, Fiat wouldn't have fitted it.

The spigot on the back of the airbox is quite fragile; dealers have been known to break them during routine servicing. AFAIK the part of the airbox which contains the spigot cannot be bought separately and a new replacement airbox from Fiat is silly money. Consequently some inevitably get bodged back together.

You need to get this fixed for two reasons; frstly the bypass hose can't work as intended if it's been blanked off, and secondly the hole in the pipe connecting the airbox to the intake is letting unfiltered air into the engine, which will lead to premature engine wear. If operating in a dusty environment (not massively likely in the UK, I'll grant you), this extra wear could be significant.

It's not a vacuum pipe by the way, as it attaches to the airbox side of the throttle plate.

Depending on the nature of the damage, you might be able to devise a means of repairing it - both plumber's merchants and garden fishpond shops may have a suitable replacement for the spigot. At least one person here has managed to find a threaded piece of brassware and fabricated an effective alternative. There's also the breakers, but be aware this is a part that's likely to be damaged or broken on one obtained from such a source, so check carefully before parting with any money.

I've just noticed this on eBay; the photo doesn't show whether the spigot is undamaged but if so, would perhaps be the easiest way forward. Make sure you first ask the seller to take a photo of the underside.

We may be able to help you further if you can take off the airbox and post us a picture of what's broken.

The easiest way if found if the spigot is broken off is to plug the hole in the air filter box and add a small filter to the end of the pipe. In the attached photo its the small blue filter in the middle of the picture. in this case I've secured it to a bracket with strong magnets.
The filters are only two or three pounds of Ebay. Search for breather filter.

Muttleysdad's idea is ingenious and looks the business, but I have doubts ...
The airbox spigot is located after the air filter, so there will be a pressure differential between atmospheric air and the air in the inlet tract, due to the resistance of the air filter - especially whenever the throttle is wide open. This design allows movement of the air-mix from the offending pipe into the inlet tract. The filter fitted by Muttleysdad does not allow for this, so the original sequence designed by Fiat will not work.
As has been said, Fiat designed the pipe and spigot for a reason.

I had chance to have a look if the spigot had been broken as suggested by jrkitching.

Yes it had been broken, and as others had said it was best to get the pipe connected again.

I managed to do a repair that was better than the original (blanked off pipe and spigot left open to atmosphere)

I reused the bolt that had been blanking off the pipe - drilled a hole through the centre along its length, then removed the head leaving a threaded tube. The bolt was M6 thread.

Where the spigot should have been I drilled ant tap M6, screwed the tube into place an reassembled.

Thanks for the replies and thoughts.

You've either got a very good drill press or a lathe!
Great idea - and a permanent, strong repair.

Thanks sweetsixteen - I wish I had a lathe ( I do have a tool fetish)
It was free hand drilled, held with mole grips and used a 500w hamer drill (without the hamer

Jernas said:

Thanks sweetsixteen - I wish I had a lathe ( I do have a tool fetish)
It was free hand drilled, held with mole grips and used a 500w hammer drill (without the hammer

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Well done for making good use of what you have

-Alex