Intermittent Knocking Noise from Engine Idling

[hal3210]

I've noticed what seems like an occasional misfire on my 2013 Corsa 1.4 SE Automatic. A few months ago, I'd notice an occasional slight knock/bang and the revs would momentarily fall slightly and then go back to normal. Now the weather is a lot hotter, I've noticed when pulling away when the engine is hot the engine bangs quite a bit with the same slight drop in revs. Whilst waiting at a roundabout today for a few seconds there was a banging sensation that I felt throughout the car. Once on the move though, the car drives perfectly with plenty of smooth power. This banging/knocking only occurs when idling and just recently when pulling away.

I've read about quite a few problems with this 1.4 Ecotec engine - I'll get it looked at by a mechanic but I just wondered what is the most likely cause?

It will be a tricky noise to show the mechanic as it's not as though it does it all the time.

The car was recently serviced with 5 W 30 oil (as used from new) - I'm sure I read somewhere that using thicker oil could help but is this likely to be of help in my case?

Many thanks in advance

[voram]

Whatever it is I doubt it's anything to do with oil. My personal bets would be,
Most likely - ignition system.
Next most likely - fuel injection.

[E-bmw]

If it isn't registering a missfire I would say engine/gearbox mount personally.

[hal3210]

Many thanks for the replies. I've made a YouTube video which hopefully shows the knock - the misfire happens at roughly 10/18/22/31/34/43/50/57 seconds and 1min 06 seconds on the video.

https://www.youtube.com/watch?v=KDtl6ZeVGog

The engine does move slightly each time the knock occurs

[GreenV8S]

I don't hear any knocking, but that looks like a stumble caused by a misfire.

[shakindog]

Coil pack and plugs would be my bet.
They tend to corrode on the spring inside the rubber boot causing resistance which in turn causes a misfire.
Will start off as an occasional thing and get worse as time goes on.
Remove the plug at end of coil pack then the 2 torx bolts. Pull up on the coil pack may need a wiggle but it will come.
Turn it upside down and look down each hole.
One or more will be green and furry that’ll be the issue.
It’s easier and less hassle to just replace the coil pack.
Change the plugs too as can cause corrosion on the end of plug.
The corsa Will only usually throw a code when it’s actually misfiring when it’s not the eml light will go off and it won’t be stored it’s a weird set up by Vauxhall.

Just my opinion of course others may know more than me this is the internet after all

[hal3210]

Many thanks for the replies, the plugs were changed recently but it does certainly sound as though it is the coil pack. I'll get the coil pack checked out by a mechanic as soon as I can.

The misfire doesn't throw up the engine management light but I suspect it would do if the misfire gets worse.

[shakindog]

Ignore me I’m an idiot and hadn’t watched the video link.

Could possibly be when the air con cutting in and out if it has it and it’s just hunting a bit as it takes up the load.

You’re doing the right thing taking it to the garage as it’s far easier to diag a car when it’s in front of someone that knows their onions

[hal3210]

Thanks again, I've just tried the car with the air con turned off and it behaves exactly the same so I don't think it's to do with the air con cutting in.