Popping noise in exhaust in idle

[GTi-Tecnix]

Let me get this clear on the term idle. Does this mean car (engine) running on stationary?? Just need to get this clear.

[GTi-Tecnix]

Having said that, with the slight vibration underneath in the cat area I do hear slight sputtering engine! Also my mechanic only has a Snap-On diagnostic scan and not VCDS, anyone have any suggestions who I can go to have it scanned?

[GTi-Tecnix]

Seems to me pudding has an eye for misfires and is a specialist in this field 

[Dan_FR]

Well why don't you follow his advice then? Bin the spacer, forget modifications like intakes, and get it on VCDS to determine if it is indeed a misfire, check nothing looks amiss, cam timing for example, check fuel trims are within spec and you don't have a leak somewhere, check you have no open circuit or electrical malfunction fault codes (not all OBD2 scanners can pick up these codes) and get it on the misfire counter to see which cylinder(s) is misfiring.

If its one cylinder, then look to swap the plug & coilpack with another and check to see if the misfire follows the plug & coil or stays with the cylinder. If it stays with the cylinder then its time to start removing the inlet and getting the injectors flow tested. If no problem is revealed here then you've more serious internal damage, ring landing for example

All the help & info you need to follow has been posted

[pudding]

The car is running fine. There is a slight vibration underneath when stationary and car is pulling as it should do; in terms of performance I can't complain really. All the down pipes and exhaust are standard nothing modified. The spark plug that I referred to earlier as being "toast" was due to black carbon. At the back tips of my exhaust there is black smoke carbon.

I heard that popping in exhaust can be caused by unburnt fuel being ignitied in the hot exhaust.

OK so we've established:-

The car is standard (pending ECU scan) except for this spacer thing on the DV. 

1 spark plug is black.

Follow Dan's advice about moving the coils & plugs around to see if that cylinder continues to run rich.  If it does, you have your answer - a bad injector.

You really need to get it to a workshop to confirm because internet diagnosis is just words.  You need to get some tools and diagnostic machines on it.

[GTi-Tecnix]

It would seem that this has nothing to do with a misfire at all. The pops in exhaust carry on after witching engine off! It’s a heat and exhaust fuel issue it would seem. Best to use vPower fuel which more pure and cleaner.