2018 Leon Cupra 300 with intermittent, unusual engine noise

[mungo]

Any ideas on this problem? Typically problems reared Friday night and can't speak to my mechanic until Monday, Car is meticulously well maintained. Mileage 85k, got it in 2023 with 45k miles. Last night on way home I felt a slight misfire that felt like it could possibly be coil pack related (I've had mk1 and mk2 Leon Cupras in the past, so know what it feels like). Then, waiting at traffic lights it stalled. Restarted. Weird rattly noise which then disappeared. Got home and opened bonnet - it would occasionally make a rattly noise, then stall. Restart - noise comes and goes. No dash warning lights. No errors reported on dash.

Any ideas what this could be? Typically, as I can't speak to my mechanic until Monday, I am worrying something serious. Trying to attach video to a link ... if anyone has seen this before / is a mechanic, would be grateful for any hint at what it might be

https://drive.google.com/file/d/1_PNzam-VZeQo1q_pBAu1rYI70CtZoYtJ/view?usp=drive_link

 

[mungo]

Update - cold start about 20 mins ago. Sounds worse, engine shuts down - engine warning light now on.

I will update everyone here when I get it looked at, I won't not put up the useful information like most seem to do after reporting a problem.

 

[mty12345]

Can't see the google drive link, says access denied

 

[mungo]

Can't see the google drive link, says access denied

thanks for letting me know - I just granted access for someone that clicked on it. I'll just try and make it accessible.

Edited to add: just made it public, apologies, I didn't realise it was private.

 

[mungo]

This was it on cold start this morning

20260425_084543.mp4

drive.google.com

Glad I have a motorbike while I wait to get the car looked at!

 

[Mo_86]

Get that on a proper diagnostics and don't start it again i say.
Could be running on just 2 cylinders by the sound of it.

 

[mungo]

Get that on a proper diagnostics and don't start it again i say.
Could be running on just 2 cylinders by the sound of it.

Problem I have is I need to get it the 2 miles to the garage. What's concerning me most is the rattly on and off noise. Misfire alone and I would just assume coil pack or something, but the rattly noise is more than unnerving.

 

[Mo_86]

Problem I have is I need to get it the 2 miles to the garage. What's concerning me most is the rattly on and off noise. Misfire alone and I would just assume coil pack or something, but the rattly noise is more than unnerving.

That's the reason why i wouldn't start it let alone drive, best to get it recovered.

 

[mungo]

That's the reason why i wouldn't start it let alone drive, best to get it recovered.

I think that might be the best course of action.

Anyone know why this noise is on and off intermittently?

 

[tracktoy]

If you have engine warning light on the dash then there will be stored DTC Codes, what codes are showing.

 

[mungo]

If you have engine warning light on the dash then there will be stored DTC Codes, what codes are showing.

No faults showing on car displays like they normally do for other things. I don't have a plug in diagnostic tool for this car.

 

[mungo]

Ok .... I DO have an OBD scanner and was lurking in my garage. I forgot I bought one years ago and used on my old mk2 Cupra.

Codes as follows ...

1. P0131 02 Sensor Circuit Low Voltage Bank 1 Sensor 1

2. P0303 Cylinder 3 Misfire Detected

3. P0304 Cylinder 4 Misfire Detected

4. P0300 Random / Multple Cylinder Misfire Detected

 

[tracktoy]

Sorry dont know the answer hopefully other experts will.

The P0131 is Lambda sensor related and I had to replace mine at just under 50k so thats a possible failure

Missfires have a look at https://obdeleven.com/p0304 gives you some things to look at and check.

 

[mungo]

Sorry dont know the answer hopefully other experts will.

The P0131 is Lambda sensor related and I had to replace mine at just under 50k so thats a possible failure

Missfires have a look at https://obdeleven.com/p0304 gives you some things to look at and check.

Thanks, TT. I ran the codes through AI and it seems to think it's the coilpack now. Thing is, I had a Mk1 Cupra R (did 180k miles in that one) and a Mk2 Cupra, both remapped, and coil pack failures felt rough, but they never sounded as bad as this one - and so far I have kept my LC300 standard.