I have a 2006 Focus 1.6 LX petrol, about 65k miles which we've had since it was about a year old.
It's doing well except last year it started to misfire on one cylinder when I'd just set off for France, and I didn't want to stop so I did about 500+ miles on three cylinders over a week. I did replace the plugs and leads (I think) but that didn't cure it.
When I got back I changed the coil pack and it fixed the permanent misfire. I did expec the car to fail the MOT on emissions as it smells very petrolly, especially when cold, but it passed with no problem.
For months now it misfires a little but only when under load - when revs are low in a gear and I give it some beans. Just a single misfire. It's fine once the revs are up (in any gear) and trundles along quite happily in excess of the max legal speed if asked.
I'm thinking I should probably do something about the misfire, but I'm not sure what. I'm certainly not about to spend a lot of money on it. It isn't due a service on mileage, and I've done less than 10k miles since the incident above so I'd hope that the plugs and leads were OK.
So what would folks recommend?
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I'd recommend moving this thread to Technical.
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smokie, not sure if it was relevant but I had a similar problem with my old Mitsubishi and I set the plug gaps correctly and that helped....for a bit. Like yours fine at high and hard revs but 30mph in 4th/5th keeping momentum and mine was a constant misfire until over 1500rpm.
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>> it misfires a little but only when under load - when revs are low in a gear and I give it some beans. Just a single misfire.
I spent 14 years diagnosing and fixing faults such as those by using a Sun or Crypton engine analyser, but things have moved on a tad since then :)
Loads of stuff on the internet/YouTube to help you, such as :
"Intermittent misfires are the worst kind to diagnose because the misfire comes and goes depending on engine load or operating conditions.
They seem to occur for no apparent reason. The engine may only misfire and run rough when cold but then smooth out as it warms up. Or, it may start and idle fine but then misfire or hesitate when it comes under load.
Also, it may run fine most of the time but suddenly misfire or cut out for no apparent reason. Intermittent misfires can be a real challenge to diagnose"
www.obdii.com/articles/Diagnosing_Misfires.html
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Has it got any warning lights and have you had the codes read?
I bought a cheap code reader (£15) that paid for itself immediately and has done many times over since. Son-in-law bought one of these that shows live data: www.ebay.co.uk/itm/Kkmoon-V2-1-Mini-Bluetooth-OBD2-Car-Scanner-Diagnostic-Tools-Codes-Reader-W8H3-/111889172497?hash=item1a0d1d4811:g:0boAAOSwoydWqclX
I'd wonder about the thermostat, does it run cold. Also the MAF. Apparently they may be diagnosed by unplugging them and seeing if it affects the running.
Last edited by: bathtub tom on Mon 19 Sep 16 at 13:05
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It runs at the right temp. I haven't had the codes read (and can't without paying someone or buying something) and there are no warning lights. I am not really *that* bothered by it, I just have to remember to not be going too slow for whichever gear I am in. (cue clothes jokes...)
However I will have a root around on the net cos I think I found a way to get the last code from dashboard flashes or something - I think a paper clip might have been invovled but that may have been on an old Vauxhall I had.
Checking the spark plug gap (and condition) is within my scope, also that the leads are all attached properly and not dirty, so I'll start there guess. I can look up where to find the MAF and see if I can disconnect that.
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common issues on the Zetec engine are leads and coils .Were these original Ford parts or aftermarket?.These components are super critical on these engines.Also check the connector plug to the coil.These have a habit of coming loose because there is not enough free slack in the wiring harness.
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Tisn't a Zetec engine (I think). The coil thing I put in was a cheapie off eBay as I wasn't sure it would fix the problem. As I said, checking the plugs, cables etc is something I can do so I'll have a go one day soon.
Thanks for the tips.
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If they're multi-electrode plugs, then the gaps should already be pre-set. Any adjustment of the gaps can shorten their life as the spark will always travel the shortest distance and prematurely wear out one electrode quicker than the others if you don't get the gaps exactly the same, which would be near on impossible.
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Ford Focus II - Focus misfire - Dog
