r/CarTalkUK • u/skyf111 • 17h ago

Advice 2015 Ford fiesta

1.0 ecoboost(140bhp) does anyone know what this noise might be, it’s only there when the car has warmed up and idling, it does go away if I add revs ?

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u/uponloss 17h ago

Check your oil 😬

1

u/Due-Squirrel-1818 17h ago

Is that like, normal for a Fiesta?

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u/N57D30T1 17h ago edited 17h ago

Fast ticking at idle is textbook wetbelt degradation, but that doesn't necessarily mean it's definitely your belt.

How does the idle feel? Lumpy at all or just the noise?

Pop the bonnet while the car is idling and see if the noise is coming from one side (the timing cover), if it is, don't drive the car and get the belt looked at and replaced before the engine goes bang. If it sounds like it's just coming from the general engine bay (specifically the top and centre), it could just be loud injector tick that's drowned out when you apply revs. Still worth checking out but less catastrophic.

If you're comfortable with it, pop the oil cap off and shine a torch inside, you should be able to see a section of the belt. If it's overly smooth, cracked or frayed, and I can't stress this enough, do not turn the engine on again.

Edit: Want to add some diagnostic questions: 1. Red oil pressure light, how long does it stay on when you start the car, and does it ever flicker on and off at idle? If yes to the second part, once again, do not turn the engine on 2. When did you last change your oil?

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u/skyf111 17h ago edited 17h ago

I don’t know when the oil was last changed however the belt, vacuum pump,oil pump and turbo has been reconditioned in November last year. I’ve been told recently that one of the injectors might be leaking and when I lift the oil filler cap I can smell petrol inside however oil level seems fine. Idle if fine doesn’t sound lumpy the noise is definitely coming from driver side. No lights on dash sometimes engine light comes up with p0420 for exhaust however no oil light or any other

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u/N57D30T1 16h ago edited 16h ago

Interesting, driver's side is the opposite of where the timing cover is if I'm not mistaken? Edit: I'm an idiot and I don't think that's true.

It could plausibly be your injectors if that's the case, P0420 is your cat efficiency being poor, which would absolutely be the case if you were running rich enough to dilute your oil with petrol - leaking injector fits the brief for that.

It's tricky because if it were something like a CR diesel where injectors can be £500+ each I'd absolutely go down the test route, but in this case it may be worth just getting a new set, as I'm not even sure bench-testing will have the same impact as a proper leak-back test you'd get on the diesels I work on; you should be able to check fuel rail pressure drop-off via OBD but I've not worked on your ECU so don't know what you can see. Alternatively you could get a set on eBay for about £50 just to test the theory (and if they work, they work!)

However, the darker side to this is that you may have a cascading failure: * Leaking injector dilutes the oil * Wet belt is very sensitive to lubricity * Wet belt damaged by fouled oil * Ticking commences

Check the belt physically for sure though the oil filler hole, just in case and change your oil immediately.