my Focus started misfiring yesterday and the idling was going up and down randomly. Took it to my friendly mechanic today who changed the plugs as he said they were sooted.
He changed them not so long ago when I bought the car, along with the timing belt. (85k miles)
Now, he pointed out a noise on starting I have been hearing for ages. It sounds like a valve fluttering - that's what I thought it was, and was normal. He tells me, I think, that this is the ECU adjusting the cam timing (?)
He is Lithuanian, and I don't always get exactly what he is trying to tell me.
Anyway, from what I can translate, he thinks there is a problem that he is unable to diagnose right now. The ECU thinks something is wrong somewhere and is doing this fluttering/whirling type noise on startup, and is now trying to compensate for something by changing the mixture and sooting the plugs.
His idea is to wait until the problem gets to the point where it can be reliably diagnosed.
There was a fault code, but only in the lambda sensor after the cat, which he is dismissing as not much to worry about right now and nothing to do with the current problem.
I'd like to know that this whirling, fluttering noise actually is, and how it might relate to the other symptoms. It is literally... Crank, start, whirrrrrrrrrrrrrrr for 1 second or so, normal.
I've always dealt with the obvious first and then see what's left. I think if it has a problem with the Lambda sensor it's not going to get the mixture right and that would soot up the plugs if it's too rich.
I've always dealt with the obvious first and then see what's left. I think if it has a problem with the Lambda sensor it's not going to get the mixture right and that would soot up the plugs if it's too rich.
Without hearing it, it makes me think of a starter motor not disengaging as quickly as it should. But I haven't heard it for so long that I don't even know if they do that any more. Having said that, I think your mechanic would recognise that fairly quickly.
Without hearing it, it makes me think of a starter motor not disengaging as quickly as it should. But I haven't heard it for so long that I don't even know if they do that any more. Having said that, I think your mechanic would recognise that fairly quickly.
Hard to say. But I don't think there's any way at all the ECU can control the cam timing. Surely it's a few toothed wheels, a belt, and a tensioner? If it was possible to control it, and it got it wrong, I think the failure would be disastrous :-) BICBW. I don't think your valves can be fluttering - especially just for a second or so.
If you've an engine that stays still when you crank it (unlikely), maybe try the wooden-stick stethoscope thing, while you get someone else to start it up?. TBH, I like to use a large piece of soft-but-reinforced plastic tube instead, since it doesn't matter if the other end moves, but then you have to hold it more firmly on wherever you're pressing it. But only up the top half of the engine, for safety's sake. Could at least eliminate valve noise as a source?
It's probable that the OP's car has the Duratec Ti-VCT engine. This uses oil pressure to adjust the relationship between the cam pulleys and the camshafts to optimally adjust valve timing. The control is via ECU- controlled solenoids.
A common failure mode starts with a rattle at startup, but may have more than one cause. The OP needs to find a mechanic with experience of these engines.
If interested, here is a video showing how they work:
It's probable that the OP's car has the Duratec Ti-VCT engine. This uses oil pressure to adjust the relationship between the cam pulleys and the camshafts to optimally adjust valve timing. The control is via ECU- controlled solenoids.
A common failure mode starts with a rattle at startup, but may have more than one cause. The OP needs to find a mechanic with experience of these engines.
If interested, here is a video showing how they work:
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Chris
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There is no timing control by ECU on any petrol Focus AFAIK.
I would get the cam belt timing checked independently.
Assuming the above is OK , then you (or a mechanic) need to check what temperature the ECU thinks the engine is at. A faulty sensor may make it think it is -40 and give a very rich mixture, I have seen this before.
No point changing the plugs, it won't cure the fault.
Leaving it running over rich will ruin the catalytic converter.
My bet on the noise is that it is one of the heater flaps adjusting itself.
Is that hydraulic tappets, or (as it sounds) something much more complicated? My sodding Fiesta has shims that make it a trifle annoying to adjust - I've no idea why they didn't use hydraulic tappets. Even my missus' old Capri had them.
When the engine stops and it attains its rest position, spring loaded plungers lock it in place. That's so the timing doesn't 'flutter' whilst the oil pressure gets up.
A brief rattle at startup might be a fault with the plunger, or the spring broken. A vehicle that hasn't had regular oil changes may have problems with the valve sticking. A common failure mode starts with a slight oil leak, and I guess it means the pulley has no oil in it when first starting. No repair parts are available.
Later cars have improved reliability, and once fixed so will the OP's. It's usual to change both pulleys, both solenoids, and of course it will need a cam-belt kit. Cost from £600 to £800 maybe, depending on who does it.
Many folk will think 'why all that bother' but if you have driven a Focus with the standard 1.6, then the one with VCT, you will know!
I have a 2011 Fiesta with that engine, and it is not only quite nippy, but it has great low and mid-range torque. You can drive out of low speed corners in third gear when you might have expected to need second, floor it and it goes!
It's probable that the OP's car has the Duratec Ti-VCT engine. This uses oil pressure to adjust the relationship between the cam pulleys and the camshafts to optimally adjust valve timing. The control is via ECU- controlled solenoids.
A common failure mode starts with a rattle at startup, but may have more than one cause. The OP needs to find a mechanic with experience of these engines.
If interested, here is a video showing how they work:
What a brilliant video so thanks for sharing that Chris.
Whilst I have no personal need of such information (yet anyway ), I now have a fairly good understanding of how it all works (to the point where I consider it 'simple' (conceptually)) and the questions that were popping up in my head were all answered as the video progressed (like if / how the system could be 'held' in any one position ... how it would release the oil from one 'side' whilst adding it to the other and how the relative timing was achieved etc).
The pdf Gareth linked to would probably fill in any further technical questions but I'm not sure I would have been able to understand *as easily / clearly* how it worked from that alone.
But then I guess the value of such a video would be a function of the experience of the viewer. For me for example, after watching the video I could imagine what all the actual parts would look like ITRW and even strip it and fit a service kit etc (assuming I had any special tools needed etc). I even spotted the various seals that I assumed would be needed to be able to retain pressure whilst allow movement and engineering tolerances, thermal expansion and wear etc.
I think that video is an example of how *I* would typically learn how something worked best ... where others may not appreciate that over say the direct physical approach or a paper manual etc.
A question on the functionality though ... whilst a liquid can't be compressed and so makes a perfect 'rigid' adjustment mechanism for something like a camshaft (or tappets / auto tensioners etc) where the torsional loadings vary tremendously, even over one revolution ... is it wholly reliant on retaining the oil pressure for any particular setting or are both the input ports open when the solenoid is in the holding position to overcome any leakage (I don't think they are / can be)?
eg. On a worn system and at a constant rpm within the variable timing range, could an oil leak form either chamber system then allow the camshaft(s) to gain some drive slack?
If it could then I guess that could be overcome by simply 'refreshing' the current setting every second or so (as with dynamic ram etc).
Or pressure sensors in the oilways to the crankshafts and after the solenoids? Although you could trigger fault event if it was noticed the cam timing fluctuating outside a predicted tolerance range and relative to the desired position / range?
What a brilliant video so thanks for sharing that Chris.
Whilst I have no personal need of such information (yet anyway ), I now have a fairly good understanding of how it all works (to the point where I consider it 'simple' (conceptually)) and the questions that were popping up in my head were all answered as the video progressed (like if / how the system could be 'held' in any one position ... how it would release the oil from one 'side' whilst adding it to the other and how the relative timing was achieved etc).
The pdf Gareth linked to would probably fill in any further technical questions but I'm not sure I would have been able to understand *as easily / clearly* how it worked from that alone.
But then I guess the value of such a video would be a function of the experience of the viewer. For me for example, after watching the video I could imagine what all the actual parts would look like ITRW and even strip it and fit a service kit etc (assuming I had any special tools needed etc). I even spotted the various seals that I assumed would be needed to be able to retain pressure whilst allow movement and engineering tolerances, thermal expansion and wear etc.
I think that video is an example of how *I* would typically learn how something worked best ... where others may not appreciate that over say the direct physical approach or a paper manual etc.
A question on the functionality though ... whilst a liquid can't be compressed and so makes a perfect 'rigid' adjustment mechanism for something like a camshaft (or tappets / auto tensioners etc) where the torsional loadings vary tremendously, even over one revolution ... is it wholly reliant on retaining the oil pressure for any particular setting or are both the input ports open when the solenoid is in the holding position to overcome any leakage (I don't think they are / can be)?
eg. On a worn system and at a constant rpm within the variable timing range, could an oil leak form either chamber system then allow the camshaft(s) to gain some drive slack?
If it could then I guess that could be overcome by simply 'refreshing' the current setting every second or so (as with dynamic ram etc).
Or pressure sensors in the oilways to the crankshafts and after the solenoids? Although you could trigger fault event if it was noticed the cam timing fluctuating outside a predicted tolerance range and relative to the desired position / range?
In my Googling about this I discovered the soldenoids are driven by a pulse width modulated square wave. it is not an open/shut action, the solenoids are constantly activated.
(I was wondering if the rattle I hear at startup is actually at the fundamental frequency of this modulated square wave)
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