Evening! First post here!

Having some difficulty diagnosing a fault on my 2003 (post facelift) punto petrol 1.2 8V.

Sudden loud sound on motorway accompanied by loss of power and check engine light (just about driveable, managed to get it home!).

MES reading error code for misfire of cylinder 4.

Checked coils, both OK. Replaced plugs and HT leads, no difference.

Basically it starts, just about. Idles horribly with much unevenness and shaking of the car. Revs OK, but with horrible engine knocking/clicking sound at 2000-3000 (can read this on knock sensor as cylinder 4 and see spark plug advance). Try driving it, and you can feel the lack of power, really struggle to rev once in gear. Limp!

Any ideas appreciated!

switch coils and see if missfire will move

lozenge said:

Evening! First post here!

Having some difficulty diagnosing a fault on my 2003 (post facelift) punto petrol 1.2 8V.

Sudden loud sound on motorway accompanied by loss of power and check engine light (just about driveable, managed to get it home!).

MES reading error code for misfire of cylinder 4.

Checked coils, both OK. Replaced plugs and HT leads, no difference.

Basically it starts, just about. Idles horribly with much unevenness and shaking of the car. Revs OK, but with horrible engine knocking/clicking sound at 2000-3000 (can read this on knock sensor as cylinder 4 and see spark plug advance). Try driving it, and you can feel the lack of power, really struggle to rev once in gear. Limp!

Any ideas appreciated!

Click to expand...

The rough running and knocking is down to it not running on all cylinders. This is what is causing the engine light to come on. Main concern is that you said 'sudden loud sound', that sounds more like a mechanical issue than ignition.
I had a similar issue on a Mk2, and basically it lost compression in 2 cylinders, that was the end of that car although i did manage to sell it for spares.
I would suggest a compression test on the cylinder that isn't firing, just to make sure. if the compression is ok then it most likely to be an ignition fault.

Thanks both, will try the coil switching and compression test.

If it's not a simple fix as you say it's not worth it so will probably scrap and get a newer one!

Will let you know what I find.

Hi'

What did you find ???