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My Toyota Vitz 2007 idles very rough. Sometimes it stalls if I suddenly stop after few miles drive.

I took the vehicle to a mechanic and he cleaned up the fuel pump. He used compressed air to clean up. When he tried to clean the top part of the pump (I don't know the exact name) it blew up. There was some sort of a black colored powder inside it.

Mechanic told that the purpose of it is to remove any fuel vapor from the outgoing air when filling the tank and that part is not vital. He just re assembled the pump and installed in the car again. Now I am driving with the damaged fuel pump.

The rough idling problem hasn't got resolved either.

So, is it OK to drive the car with this damaged fuel pump?

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    It sounds like the charcoal canister is what blew up. You'll probably want to replace it, especially if you have emissions testing. Have you checked the fuel pressure while running to see what it is doing? – Pᴀᴜʟsᴛᴇʀ2 Nov 24 '15 at 2:09
  • @Paulster2 Mechanic didn't test fuel pressure at all. So can this damage cause a less fuel pressure or it only affects emission? – Softcode Nov 24 '15 at 4:29
  • You have two issues here: charcoal canister; fuel pressure. I'm suggesting you have the fuel pressure checked while running to figure out if there is a problem with your fuel pump. Who knows if the mechanic screwed it up or not. I'm trying to help you diagnose your rough idle issue, which the mechanic seemed to think your fuel pump might be at issue. – Pᴀᴜʟsᴛᴇʀ2 Nov 24 '15 at 12:45
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The black powder was charcoal from the evaporative fuel filter/canister. This filters evaporated fuel from your fuel tank. When your fuel tank gets warmer and the gasses expand above the fuel line they pass through this canister and are filtered out by the charcoal. When the temperature drops a reed valve opens due to the pressure change in other direction and the vapors are drawn into the intake manifold and are burned off by the combustion process.

This is NOT your fuel pump and blowing air through it is a way of unclogging it. If it is clogged it can cause pressure build up in your fuel tank under certain circumstances. This component is a part of your emissions system.

Your rough idle issue is more than likely caused by another problem. If you take your vehicle to a local auto parts store they can attach a 'code reader' to your car and check for error codes. If you can post your error codes with your rough idle issue under a new question someone on the site will attempt to answer that question with the error codes as hints as to what your idle issue is.

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