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Pulling my hair out


ChrisM41
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Since ive had it my 2005 Focus (1.6 Ti-VCT) has had miss fire/jitter at low/part throttle, especially when cold. It sees fine at full load and higher speeds. The idle seems reasonably stable but tends to wander by 20 or so either way.

To date i have changed the coil/leads and plugs, had the injectors cleaned, swapped out the MAF and the throttle body for known good units. Nothing has changed. As far as I can tell the coolant sensor is OK,  and there are no error codes or odd looking readings. On occasion i think the problem has gone only for it to get suddenly return again.

 

Anyone got any ideas?

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have you had fuel filter changed recently to genuine ford, mine get but jerky now and then low revs, mine a diesel thou, have you thought about getting terraclean done clean the carbon deposits will run like a dream

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I think it goes beyond that. Its mostly OK under load and at high revs. Its intermittent, a bit, some days worse than others. Today it  was properly kangarooing. Ive done everything i can this side of a compression check. Ill return it to the garage tomorrow.

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All Focus MK2/MK2.5 petrol engines do not have a serviceable fuel filter. There is only a large mesh strainer at the inlet side of the fuel pump inside the fuel tank but this is not a serviceable part. 

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you need the car looked at it could be a vct issue timing issue cluster issue ecu diode issue fuel pump injector etc only live data will help

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Yeah its going back tomorrow. Clearly its not a simple thing, the usual fixes have done nothing.

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Well I booked a PCM update at an independent. Got there and their computer was down, so in my grumpiness i decided to do it myself with Elmconfig, too hell with the risk. Flashing process went smoothly, took all of 4 minutes, and the car is now a LOT better. I'd say 95% better.

 

There is the occasional stutter, but its like once every 10 minutes, not almost constantly as it was before, and the drivability has improved a lot. It also seems faster and more economical. It amazes me that the car has spent 10 years like that.

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it amazes me ford are so lazy they don't include it as part of a service try putting some dilectric grease on either end of the leads

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Yeah done all that, im think its as smooth as its going to get. Its now very tolerable, not the smoothest car ive ever had, but OK.

Never had a car thats needed a PCM update before, every other car ive had has just worked from day 1.

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Damn and blast it. Its doing it again, just the same as ever. It lasted about 2 days and the stutter/hesitation is back just as much as ever. The long term fuel trims at idle are even worse, as low as -35% now. What on earth is going on?

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Hi, Have you carried out a compression test on all the cylinders?   This sounds exactly like a problem I had a few years ago on a BMW. It transpired I had a leak path between two adjacent cylinders.  Very intermittent depending upon temperature.  Just a thought. 

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Going to try that later in the week. Need to see if i can borrow a tester, thanks.

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Any moisture dripping from the exhaust, even after its warmed through?

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the idle wont sit stable this is due to the ecu monitoring and adjusting for low emission it can be 720-780 rpm 750 mainly so 30 either way secondly these are nit the smoothest of engines anyway a slight stumble at idle is common ford revised the newer engines with better engine mounts and different maps to smooth it all out amount other changes it will be worse when cold as that's when you get the highest emissions I found gapping the plugs to 1.1 mm and adding dielectric grease to both ends of the spark plugs helped a lot

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You do mean 'both ends of the spark plug leads' don't you? :tongue:

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Well ive done a compression test with the engine cool, all 4 cylinders are the same, at about 130psi, although the gauge used was old and battered, so no idea of accuracy. Im more interested in the fact that the pressure was exactly the same for all 4 cylinders, so it seems to indicate no issue there.

 

Ive cleaned all the electrical connectors i can get to, including the PCM connectors and the fuse/relay box, with contact cleaner in the hope that something was dirty. My journey home was mostly hesitation free, but ive been there before.. it just comes back.

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lol yes i meant the leads thats the joy of working nightshift the brain wasnt engaged.ide suggest the plug gap check and the dielectric grease and not to expect it to be a smooth engine the zetec engines never were in my new car at idle you cant even hear the engine or feel it very strange after having fords some good fuel or treatment and a good blast can also help

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Is the coolant temp sensor ok, try unplugging it, fan should come on and EML. Do they have post cat sensors?

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you got two cats and 2 sensors I'm afraid clearly visible at the bulkhead side of engine looking down

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Im replacing the coolant sensor today. The car is running rich, but im still not sure why, whether its a misfire causing the richness or the richness causing the poor running.

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How quickly should the car complete emissons readiness tests? Most complete quickly, but the catalyst ones are taking forever, they stay at 'incomplete' for weeks. I dont do a lot of mileage, but even so.

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