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Ford Mondeo Knocking Sound/Rough Engine when idle


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Hi Everyone,

Hope someone could shed some light on a problem i've been having the last 2-3 years and what the possible cause/resolution is.

I basically have a Mondeo Estate 2.0 TDCi 163 Titanium (2012 Diesel) Automatic, and love driving it, however at times when the car is idle
for example, stopped at traffic light/waiting at a junction the:

- Car Makes a knocking sound - not very loud, but you can here it go tap, tap tap more so coming from the engine bay.
- Car Sounds like its running rough - like its the engine or something. I have got out of the car and checked but I can't pinpoint anything.
Even the exhaust sounds rough when it decides to do this.
- Car Vibrates unusually, Myself and anyone in the vehicle can feel it, on/off/on/off

but the minute you press the accelerator, all these symptoms go and the car drives fine again.
On the next stop, symptoms may/may not return, so its not a problem set in stone or having permanently but disappears and comes back.
i.e problem occurs at a traffic light, but when I get home and car is idle, no sign of it.

I have told the garage I get it serviced at every year to look into the problem, but each time they look into it, the car doesn't fault - and they say they can't diagnose it.
They've told me no faults are logged so they have nothing to go by either.
This is why i'm going round in circles as the car only does this at such random times. For example, a trip to the supermarket one day, not one symptom happens.
Give it a few days, I have noticed no symptoms, but on the odd occasions, such as when I returned from the shops today, symptoms come back again when car is idle.
I'm not sure if its the car telling me theres an issue, or from reading other posts, because its a diesel some have said expect some vibrations.
But when it happens, I get nervous as if the car might stall out or something, you can literally feel yourself moving when it vibrates.
The garage have said it may be some dirt related to being diesel, and have put some additive in think its some type of cleaner, told to do long runs, but still i'm with the same issue up to today.

I would appreciate if anyone has any advice or can pinpoint what or where I need to go or look at from here.
Car has oil changes every single year, and I look after it to the best I can, just cant work out whats wrong.

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Consider the engine mounts... don't know about the mk4, but the Mk3 has got a centre mount underneath the rear of the engine that deteriorates. 

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Hi Nick,

Thanks for your reply. I'll keep that in mind and mention this to them.

Kind Regards,

Cal

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22 hours ago, cnet said:

Car Makes a knocking sound - not very loud, but you can here it go tap, tap tap more so coming from the engine bay.
- Car Sounds like its running rough - like its the engine or something. I have got out of the car and checked but I can't pinpoint anything.
Even the exhaust sounds rough when it decides to do this.
- Car Vibrates unusually, Myself and anyone in the vehicle can feel it, on/off/on/off

Have a listen in each front wheel arch while it is making the tapping noise. If it is much more apparent from the left (gearbox) side, then it is likely to be the DMF. It may be not very serious, my car has been doing something like this for a few years now. At idle there is sometimes a regular clank-clank, with a slight change in engine speed / note as it does it. It does not seem to be getting worse in any noticeable way, so I ignore it.

My clutch and DMF may have done 180,000 miles, so I feel they deserve to make a few odd sounds if they want to!

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Thank you @Tdci-Peter& @Mondeo13

I'll keep an eye out for the sound @Tdci-Peter, thanks for reconfirming yours has had it for years.
It sounds very similar to mine, its more of an annoyance/worry, but simply just goes away and doesn't get worse.

Thanks for your advice too @Mondeo13, if its just the dpf/soot burning, at least its peace of mind its nothing serious.

Kind Regards,
Cal

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22 hours ago, cnet said:

thanks for reconfirming yours has had it for years.
It sounds very similar to mine, its more of an annoyance/worry, but simply just goes away and doesn't get worse.

It does depend on the location of the noise.

DPF regen does often affect idle, I have not heard it myself (no DPF!), but I know others have. I would expect extra noise from poor combustion caused by late fuel injection and other tricks used to heat up the DPF for regen to come from the engine block and exhaust system.

DMF tapping will be local to the clutch housing, hence from the left wheel arch.

I have always been aware of having a DMF, and avoided high torque at low rpm. A diesel will pull quite hard from about 1200rpm, but the amount of movement induced in the DMF rises very sharply as rpm drops. So I use very cautious throttle control below 1500rpm, real old Granny stuff, or change down if I want to boot it. I only ever open up to full throttle above about 1800rpm. It will not make a DMF last forever, I suspect, but it can add a lot of miles to it.

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Hi again , you mentioned traffic lights , im not sure where youre driving but if the car isnt getting up and out where it can travel at reasonably high speeds it can develop dpf problems like a clogging of the fuel feed / vapouriser, car could be trying to clean too often , it may not be dpf but if you suspect it is then pour in a dpf cleaner on a pretty full tank and take it for a good hours drive and get up the speed for a good part of it and it should settle down , as if it doesnt clean out it will send bad signals to exhaust sensor and headaches will begin

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