My 06 reg Focus 1.6 Zetec petrol has an intermittent fault which is getting worse and driving me mad!

When being driven at steady speed, usually between 2 & 3000rpm, i feel a slight hesitance from the engine which feels like a misfire but I'm not sure that's what it is.

Under aceleration either gentle or hard the car performs perfectly, the hesitance is only when running on steady throttle.

I have done the dashboard computer test but no DTC codes are logged and i have also had it hooked up to a diagnostic rig but again no fault codes are evident.

The problem only occurs when the engine is at working temp and sometimes when the fault has been evident the car will idle roughly, but only for a couple of seconds at a time. Again, following the rough idling the car will drive away perfectly normally.

I appreciate that without fault codes this kind of thing is hard to pin down but i would welcome anyones ideas on this.

I am keen to avoid the 'change this sensor, change that sensor' scenario as i could spend a lot of cash before solving the problem and accept that i may have to simply wait for it to get worse to the point that the problem becomes more obvious.

Anyway, anyones advise or suggestions would be appreciated.

some of the early focus's had the same problem with the washer jets as the fiesta. Check the washer jets on the bonnet to see if there is a rubber gasket between them and the bonnet to stop rain water seaping past and onto the engine. if not order a set of new jets fron ford, they are easy it fit and come with the gasket. Then you will need to check the spark plugs and plug leads as the rain water runs in to the spark plug area in cause's them to break down. Look for sign' of residue in the spark plug area.

Finally got to the point this week where the engine warning light came on for a trip to work and back. Misfire got worse during these two journeys.

Next day the light didn't come on and the car behved normally, however I have had the codes checked today and the fault logged points to a faulty coil pack.

Plan to get this replaced early next week.

Finally got to the point this week where the engine warning light came on for a trip to work and back. Misfire got worse during these two journeys.

Next day the light didn't come on and the car behved normally, however I have had the codes checked today and the fault logged points to a faulty coil pack.

Plan to get this replaced early next week.

glad you found the problem, but i would get it sorted as soon as you can before you end up needing to replace the cat too. unburnt petrol going into the cat causes it to fail

I have had this problem but have had no EML.

Had full diagnostic and it came up with P0602 Control Module Programming Error.

Garage is taking it Tuesday. Fingers crossed!

(But glad I have found someone with the same symptoms)

glad you found the problem, but i would get it sorted as soon as you can before you end up needing to replace the cat too. unburnt petrol going into the cat causes it to fail

Was worried about the possibility of damage to cat so had the coil pack replaced today, thankfully not as expensive as I feared. Found a good local garage which didn't charge for the diagnostic check, just for parts and labour, though I think I could have replaced the coil myself.

Seem to have my misfire problem sorted but noticed that even when ECU had logged the coil fault there was no DTC code listed when I did the dash computer diagnostic check.

Do DTC codes have anything to do with ECU error codes?

Seem to have my misfire problem sorted but noticed that even when ECU had logged the coil fault there was no DTC code listed when I did the dash computer diagnostic check.

Do DTC codes have anything to do with ECU error codes?

DTC (Diagnostic Trouble Codes) are error codes generated from the ECU. Even when a fault has been cured the DTC remains stored until they are reset.

I wouldn't trust the dash check if I were you. Having never used it myself I wouldn't know exactly what its supposed to do, but I thought it was just for checking the dials and stuff? Why would ford put a self diagnostic computer in their cars when they can charge you or I £80+ for a code read?

EDIT: After looking up the self test mode it seems that it does a fair bit, including continuous DTC's. When you did the self test you car only had an intermittent fault (wasn't there constantly) so the self test wouldn't of showed up anything.