Ford Focus - Rough idle on petrol focus

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Sun 11 Mar 2012 23:42
Ford Focus - Rough idle on petrol focus - Focus_Driver

My mk1 focus 1.8 idles at 650-700rpm when stationary and sounds like it is low on power and stutters. When driving normally it seems fine. A second, lesser problem is that sometimes it takes several turns of the engine to start up the car but other times its instant. This is at around 8 to 10c temperature. There are no engine warning lights that light up.

Further info:

Checked air filter and it is moderately clean. Oil change is not due.

Battery is showing as 12.6v on the multi-meter before starting up car so that and the alternator is fine.

Spark plugs changed recently.

Spark plug leads and coil pack appear in good condition but I wouldn't know how to check them. I believe they are the original items - car mileage is 115k.

I'm tempted to change the plug leads - is this the likely problem?

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Thu 15 Mar 2012 16:44
Ford Focus - Rough idle on petrol focus - Waino

Between around 80-87k miles, my wife's 1.6 mk1 Focus developed a rough idle and started using oil. I reported this to my local (independent) garage - principally mentioning the oil useage. They changed the pcv valve (google for it - I'd never heard of it) and, not only was the oil consumption considerably reduced, the idle was smoothed as well.

There are lots of references to the pcv valve on the net including some material on Youtube.

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Thu 15 Mar 2012 23:06
Ford Focus - Rough idle on petrol focus - Focus_Driver

Thanks, I replaced the air filter the other day and it seemed to have solved the problem.

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Fri 16 Mar 2012 12:10
Ford Focus - Rough idle on petrol focus - unthrottled

I hope the air filter has sorted it, but I've never encountered an air filter causing an idling problem.

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Fri 16 Mar 2012 23:56
Ford Focus - Rough idle on petrol focus - Focus_Driver

I'm not sure if it was coincidence but it seems to have sorted it. Does the car breathe in air while idling? If say you had an air filter which had not been changed for 100k miles and obviously super dirty, would the car idle OK and not stutter? (Assuming no problems with anything else).

I also replaced the pollen filter. It was the original ford one and the cars done 115k and it was a mess!. The air filter had been in for about 12k miles btw.

Edited by Focus_Driver on 16/03/2012 at 23:57

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Sat 17 Mar 2012 10:25
Ford Focus - Rough idle on petrol focus - unthrottled

Does the car breathe in air while idling? If say you had an air filter which had not been changed for 100k miles and obviously super dirty, would the car idle OK

Yes, but only very little. If the filter was very restricted you'd notice a (slight) loss of maximum power, but that's it. Glad it's sorted though!

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Sun 18 Mar 2012 23:46
Ford Focus - Rough idle on petrol focus - Focus_Driver

Thanks, it's still running fine so problem seems to have sorted itself.

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