Peugeot 308 Anti Pollution Light and engine rev drop with odd sounds (video)

That yellow icon is a check engine light, not necessarily anti-pollution. When that light is on, it means the computer has found a fault with something and has stored a code in it's memory for the specific malfunction. Get the code read. Many parts stores do this for free.

Your rpm drop sounds like the engine skips a beat. It could be an occasional misfire, it could be a temporary imbalance in the air-fuel ratio (mine does this often, and way worse than this) or it could be a temporary voltage drop. It's not a big deal (nothing will break because of this), but you do want to get it fixed. The code stored by the check engine light should help us narrow down the possibilities.

One thing is for sure, it's not the timing chain. The timing chain keeps the valves synchronised with the pistons so they don't hit each other. If the timing chain was in the wrong position, you would have much more serious problems (and scarier sounds) than what your engine is doing now.

Get the trouble code read, we will point you in the right direction.

There are a few common problem with the late 1.4 & 1.6 PSA petrol engines (I cant remember the engine codes of the top of my head).

An issue with which could be your problem is there is an inherent problem with the cam gears slipping, only ever so slightly so not enough to cause any damage or severe running issues but enough to 'confuse' the ECU.

Common symptoms of the timing issues are: - Crankshaft/camshaft sensor incoherence/implausibility code - Running too lean/rich code (Usually too rich) - MAP sensor code

Removing the front of this engine to get to the timing chain is a reasonably big job so a good idea is to put an oscilloscope on the crank sensor, cam sensor and number 1 injector for reference. As the timing slip is so small it takes a specialist to notice the difference, but if you have access to the waveform of a known good car the difference is clear.

If you post the your VIN number (you can leave out the last 6 digits) or engine code I can give you a load more info about your engine.

Obviously this is an assumption without knowing what your fault codes are

On your chasis number look for engine code it's in the last 5 characters if it's kfv nfu kfu these engines run fairly hot as a result the coil packs get warm as they are sat on top of the engine the solder softens inside them causing problems I usualy have a few hanging around as it's fairly common easy cheap fix £20-£25 for a second hand one usually