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Discussion Starter #1
I bought a beautiful condition 2006 MY 2.0L petrol Ghia Auto C-max (I have a back injury that means I can't drive a manual).
The car has very low mileage, and paperwork to back it up. I think the previous owner was old and used it little as it's in showroom condition inside.
I thought I test drove it enough to locate any issues and so parted with quite a lot of money to buy a 14 year old car with 54k miles on the clock.
The car works perfectly and drives beautifully, but...when I get over about 50mph and then accelerate gently (or have cruise on and reach an uphill section) the car judders and shakes until the road levels out or I ease off the throttle. Accelerating hard seems to reduce it somewhat, but it doesn't go away, again until the load on the engine drops.

When I got it it shifted harshly, and after reading lots of forums I treated it to a transmission flush and I cleaned all the solenoids (per some YouTube videos). If you're scared of this, trust me it's not that hard. This improved shifting beyond recognition, and the box is almost as smooth as the one on my old Volvo now.
But the problem could still be in the auto-box as it has an electronic overdrive in 3rd and 4th which would account for not being able to make the problem happen at slower speeds. Also, not being a transmission specialist, I don't know if issues with the bands could do this.
Another thread made me think of engine mountings - so I replaced all 3. No change, but not a huge outlay, and they were 14 years old.
And, I've replaced the plugs and coil packs as everyone told it it must be them.

Part of me thinks it could be driveshafts, but I've had driveshaft problems before, but none gave these symptoms.

Has anyone had similar, or can help me rule out the driveshafts, or the transmission, or can suggest anything else?
The car is silky smooth, and has loads of power, starts easily and is returning almost 33 mpg which I think is brilliant as I annoy BMW and Audi drivers. I am an experienced home mechanic (and restore classic motorcycles for a hobby) with 40 years of grubby T shirts, so don't like to be beaten by niggly problems like this.
Thoughts anyone?
 

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Interesting I would say the DMF but of course being an auto it does not have one? :)
You've already done what I was about to suggest the gearbox oil flush and new oil.
Does it seem to lack power when the vibration starts if so it could be a restriction in the fuel filter.
Check the wheel balance weights have not come unstuck on one of the wheels and gone into oblivion, there is a bearing on the o/s/ driveshaft centre they don't normally give trouble but when they do give similar symptoms.
Also maybe the rear shockers is worth checking I've changed quite a few of them.
Good luck.
 

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I've just had a another thought I had a Modeo a long time ago it would only vibrate after a few miles that was a bugger to sort it turned out to be a bulge in a tyre but the bulge would only show when the tyre got hot , so well worth checking for bulges in the tyres best done when the tyres are warm or over inflate them for testing purposes before returning to the correct pressure.
 

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Discussion Starter #4
Thanks Nighthawk .
The engine has loads of power when it happens. Btw, did you know the Focus fuel filter is inside the tank? Or that's what the forums seem to suggest.
If a wheel weight was lost, surely that would show up at high speed no matter if you were accelerating or not?
I will research the driveshafts suggestion again. The transmission is an expensive last resort; if I could find a rebuild kit I would seriously consider it.
I had a Honda which had a shudder over 60mph which was caused by rear shocks, but it also didn't care if you were accelerating or not it just kicked in at 58 mph and got worse the faster you went.
 

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Hiya , sorry I just just woke up as I'm on nights, I quickly read through I thought you said the vibration was above 50.
There should be 2 fuel filters one in the tank more of a gauze and one in front of the tank a canister, not that this is the problem if you still have power.
Is the box actually changing up and down the gears properly more so changing down when you accelerate or under load as it don't sound like it is (kick down)?
Also there is a big filter in the bottom of the auto box it's about £40.00 but has been known to cure a lot of problems.
 

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Discussion Starter #6
It does kickdown, when pressed, and I did replace the auto box filter when I cleaned the solenoids. I couldn't do a full transmission fluid change as I couldn't get the bottom hose off to do a proper flush, but I did swap about 4 litres of fluid, and it is at the correct level now.
I'm still suspicious of the electronic overdrive. Does anyone here know if any of the software available would tell me when it is switching in or out? I use Torque and recently bought Forscan (which I can't seem to get to do more than tell me the cars' details). but I am very computer litterate so happy to try other things.
I see no mention anywhere about what happens to the overdrive if you select gears manually; does it disengage, or work normally? There seems to be no change in revs or feel when I switch to manual at a steady speed.
 
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