Ford Focus 2011 - Uneven revs/Jerking and chugging since cam belt | Technical matters | Back Room Forum

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Fri 11 May 2018 14:49

Ford Focus 2011 - Uneven revs/Jerking and chugging since cam belt - iFocus

Hi All,

A few months ago I had cambelt was replaced by an independent mechanic and its had uneven revs and jerks/chugs at speed (and chugs in traffic too!)

It is showing no errors currently according to my ford dealer who has looked at it since the cam belt was done and they can find no issue with it.

It basically has uneven revs at idle and at speed, this unevenness manifests its self as a chug or a surge whilst driving, its especially more noticeable when going down a slight incline. The MPG has been dire since the cam belt was replaced too.

Here is a video I've taken of my rev counter and you can see when holding it at certain revs they go up and down, I've got the display in test mode so you can clearly see the difference revs more clearly.

https://vimeo.com/269179678 (apologies if I am not allowed to post a vimeo link!)

Does anyone have any idea what this might be? I'm thinking it could be the timing is out but I don't really want to fork out more money if it isn't as I'll likely have to have a new timing belt installed.

Thanks,

Craig

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Fri 11 May 2018 16:32

Ford Focus 2011 - Uneven revs/Jerking and chugging since cam belt - Railroad.

My PC won't allow me to view your video, and so I am assuming your car has a petrol engine. If the valve timing had moved for whatever reason I'd expect a loss of performance, but I wouldn't necessarily expect uneven running. What I would suspect is an inlet manifold vacuum leak, and this should be easy to determine. A vacuum gauge would confirm one way or the other, and so would a scantool showing the MAP value at idle on live data.

Edited by Railroad. on 11/05/2018 at 16:36

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Fri 11 May 2018 16:44

Ford Focus 2011 - Uneven revs/Jerking and chugging since cam belt - iFocus

It is down on power too, I forgot to add that. And yes it’s the 1.6 Ti-VCT engine.

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Fri 11 May 2018 18:10

Ford Focus 2011 - Uneven revs/Jerking and chugging since cam belt - bathtub tom

If this happened immediately after the cambelt change then that would seem the obvious cause.

Why didn't you return to the mechanic straight away?

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Fri 11 May 2018 19:22

Ford Focus 2011 - Uneven revs/Jerking and chugging since cam belt - iFocus

If this happened immediately after the cambelt change then that would seem the obvious cause.

Why didn't you return to the mechanic straight away?

I did but the mechanic span me a yarn about letting the cambelt 'bed in a little' and it couldn't possibly be the timing that is off because, in his words the car wouldn't run at all if the timing was out.

Eventually I made him take it back and he conviently didn't notice any issues but his other mechanic did. They replaced the plugs and leads thinking it was that (it had a service on the same day as the cambelt and waterpump change too).

I since found out it was my mechanics first time he'd done a Ti-VCT engine and I strongly suspect he didn't have the correct camshaft locking tool.

I eventually lost confidence with the mechanic and went to my local (actually decent) ford dealer who has checked it and without checking the timing then they cannot diagnose anything. Apparently it is showing no fault codes at all.

Annoyingly the cambelt was only done (early!) because my coolant was dropping and the mechanic said it was the waterpump leaking... the coolant is still dropping too since the waterpump has been done...

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Fri 11 May 2018 21:24

Ford Focus 2011 - Uneven revs/Jerking and chugging since cam belt - Galaxy

The cambelt doesn't "bed in". When I had the cambelt changed on my Mondeo, several years ago, the car was spot-on from the moment I collected it, which is how any car that's just had the cambelt changed should be!

I would say that someone needs to take the covers off and physically check the valve timing. If this fault occurred immediately after the cambelt was changed then that would certainly be the first thing that I would check. Of course, it could be something else that was disturbed during the change, but I'd still go for valve timing first. Another consideration is whether they've used the correct cambelt. There are often several available versions of a belt and they will all physically fit. However, they may differ slightly in the total number of teeth. I do hope, by the way, that the garage have fitted a complete cambelt kit and not just the belt.

The cambelt only needs to be one tooth out to cause rough running. If it's much more than one tooth out then the engine probably wouldn't even run.

Edited by Galaxy on 11/05/2018 at 21:26

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Fri 11 May 2018 21:31

Ford Focus 2011 - Uneven revs/Jerking and chugging since cam belt - elekie&a/c doctor

Sounds like the garage did not use the correct timing set up tools. Even half a tooth out is enough to cause running problems. Time to find a garage that has a good old fashioned vacuum gauge. This should pin point if the valve timing is out. Set tools here;www.ebay.co.uk/itm/Tool-Hub-1133-Petrol-Engine-Set...7

Edited by elekie&a/c doctor on 11/05/2018 at 21:32

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Sat 12 May 2018 17:55

Ford Focus 2011 - Uneven revs/Jerking and chugging since cam belt - John F

The cambelt only needs to be one tooth out to cause rough running. If it's much more than one tooth out then the engine probably wouldn't even run.

I don't believe this. Cam sprockets with vvt can vary by an amazing number of degrees, far more than a tooth or two. I suspect there are hundreds if not thousands of Ford engines with cam sprockets, vvt or not, faultily retightened onto their camshafts running slightly less well than they did before some careless cackhanded mechanic bodged an unnecessary cambelt change.

I suspect this is yet another example of problems caused by unnecessary 'servicing'.

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Sun 13 May 2018 21:08

Ford Focus 2011 - Uneven revs/Jerking and chugging since cam belt - iFocus

I suspect this is yet another example of problems caused by unnecessary 'servicing'.

Not sure what you mean by unnecessary servicing? Apparently the waterpump was leaking and it was replaced, rather than putting the old cambelt back on, it was suggested a new one was put on instead.

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Tue 15 May 2018 19:05

Ford Focus 2011 - Uneven revs/Jerking and chugging since cam belt - John F

I suspect this is yet another example of problems caused by unnecessary 'servicing'.

Not sure what you mean by unnecessary servicing? Apparently the waterpump was leaking and it was replaced, rather than putting the old cambelt back on, it was suggested a new one was put on instead.

It is not necessary to disturb the cambelt to change the water pump which is driven by the poly - v belt in front of it. These sturdy cambelts only drive two camshafts and a tension pulley; they are strong enough and are designed to last the life of the engine, with advisory 10yr /100,000m changes for ultimate peace of mind. Have them replaced inexpertly, possibly with an inferior product, at your peril.

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Mon 14 May 2018 13:43

Ford Focus 2011 - Uneven revs/Jerking and chugging since cam belt - Gibbo_Wirral

I suspect this is yet another example of problems caused by unnecessary 'servicing'.

What exactly is "unnecessary"? Cars need regular services. The cambelt replacement time or mileage will no doubt co-incide with a service.

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