I have a 2008 Peugeot 308 1.4 petrol. I got this car a few weeks ago, and ever since I got it, I seems to have a problem with the anti-pollution system. The anti-pollution warning light comes up to indicate a fault every time I start the car up. I went to a mechanic to get it checked with a computer, however I found out nothing helpful.

https://www.youtube.com/watch?v=M4oH0bjaOLE The icons don't actually flash, only records as if they are, beep noise is anti-pollution faulty warning.

I noticed that for some time, whenever I start the engine up and I just sit there for the first minute or so, the revs drop from 800 (what it starts at) to like 700 and then jump back up trying to get back to 800. The change of the sound from the engine is concerning and not sure what it could be.

I'll be visiting a mechanic soon to hopefully have a look at the engine. Worth pointing out - this car had the timing chain changed just before I bought it and it was suggested by another mechanic that maybe the chain is out and should be looked at.

Any advice would be much appreciated

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

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