Here I've filmed the sound on the muffler. I put a cloth against the hole and listened for sounds and the air seems to escape close to the CAT? It really sounds like it. I did a soap test a month ago looking for air leaks and found that the clamps on the CAT and muffler were leaking air under pressure. So I put some paste on it, now the leak is pretty minimal.



Maybe I accidently bought a Fiat with a Ferrari engine?

Definitely no leaks big enough to cause any problems.



You say the sound only there till it warms up ?



Sounds like its running on three cylinders ?

The idle is rough, and yes the sound is only there when it's cold. Goes away after a couple of minutes. Dunno how a 3 cylinder run would sound like, but I'm sure one time the car gave me a cylinder 4 misfire code, after removing it, it never came back. Maybe a coil pack that's causing the issue?

I normally pull a plug lead of at a time.

The cylinder that's the problem doesn't make much difference where as removing the lead from a good cylinder will make a big difference.


Word of caution.


Don't touch the leads while the engines running if you have a pacemaker.


If you do it as the engines running. Put one hand behind your back and don't touch the bodywork.


I have only takes a few seconds to do all four. I don't bother but some rubber gloves would be a good idea.


Its not recommended to run with a coil disconnected but I have had no problems for the few seconds it takes.



Its not easy to access the spark plug end but the coil packs are accessible without removing the air filter

Isn't there a better way? Last time I pulled it out I was shocked by the wire end. I saw a video on youtube where a guy formed an S from a gem and put it inside the coil and then reattached the wire on top of it. Then tested the sparks with a screwdriver.

Not really. Yours testing if the mixture is firing not just the spark. That would be stage 2


If you are worried about a shock switch the engine of in between.

Yes I did this test with my father, they are definitely sparking. The spark plugs are NGK and were light-brown last time I removed it, after replacing the O2 and MAP sensor. The wires are brand new. I noticed that one of the coils were different from the other, from a Lancia? It's like 90% of my car has parts from a Lancia.

Remove a HT lead start the car.
Replace the lead remove another start the car
And so on.

Three leads the car will struggle and rudder as it will be running on two cylinders

One lead will not make a difference as its already not firing.


There loads of reasons for it not firing. Oil running down be valve seals burning of before it will fire correctly. Or water entering the cylinder while its at rest. Or damaged cylinder head gasket and no compression until the metal expands.

But before we get into that we need to confirm the noise is due to one of the cylinders not firing.


You could pull the connector of the injector instead if you like.