Ford Focus misfire - faulty wiring into coil
My 2006 Ford Focus 1.6 Petrol Ghia has developed an occasional misfire both around town and on motorway drives. A diagnostic check by my Ford Agent service department indicates 2 possible misfire causes:
1. A wiring fault in the plug that goes into the coil - this would require taking the plug apart and resoldering new wire(s) into it.
2. An oxygen sensor malfunction. The previous owner had one of the 4 sensors replaced just before he sold it to this Ford Agent.
Has anybody had any experience of this problem - it sounds like it's a problem that's specific to this 1.6 engine.
Alternatively to re-soldering have you asked them how much a brand new length of cable complete with plugs/connectors would be?
If one of the oxygen sensors is faulty it will have a specific fault code stored and it can also be checked in the "powertrain datalogger" on the dealer diagnostic tool. If they have not done this then you have paid for poor diagnostics. All the sensors can be read at the same time and it would be quite simple to identify a poor or bad oxygen sensor.
Coil packs are a common failure on these cars too.
Last edited by Hometune; 30-10-12 at 21:46.
Personally I would check your spark plugs and leads, the early focus's (2005 build on) suffer from water entry into the plug holes from the washer jets. The wiring up to the coil pack can also be too short and under certain conditions can cause a intermittent misfire! I agree with hometune.... Ids would be able to monitor what the oxygen sensors are doing.
Thanks for all your suggestions.
In answer to Dennis W's query about the cost of new wiring, I was told the new wiring setup is about£600. I think I'll accept some soldering instead of that!
For Hometune's point about a fault code for the oxygen sensor, it did show up a code for an oxygen sensor. However, the previous owner had one new oxygen sensor replaced and I had the engine management light come on twice for this/these sensors after that. The Ford agent checked these out and suggested that the fault may be appearing because of the wiring problem rather than a fault in the sensor itself. I'll wait therefore to have the wiring re-soldered to see if the O2 sensor plays up again.
6628Claire's point about water getting in to the plug holes is very valid and mine used to get a lot of water into them. I then placed and tied a large piece of plastic (sold in a poundshop as a clothes line cover) to cover the spark plugs area and they've been dry ever since.
Hopefully, after they've re-soldered the wires tomorrow I'll be in a better situation to judge what's really causing the problem (or not causing the problem if the re-soldering doesn't work).
I had same problem with coil . I changed the coil and leads and good as new now.
Misfires often cause oxygen sensors flag up as a fault till you have sorted the misfire out dint worry about it I suggest checking thr spark plugs and areas for water dampness first then leads then coil pack.
Is there anyway of checking if a HT lead, sparkplug or coil pack is the cause of the problem as this sounds exactly the problem I've got with my mk1 focus Ghia 2.0. I generally try to do as much work as possible however the wife is currently out of work and I need to make the best educated guess before I buy bits which may or may not work?
Is it a permanent misfire? If it is, detach the lead to each cylinder in turn to determine which has the misfire.. Use either insulated plastic pliers or stop the engine each time before removing a lead.
Once you have found the misfiring cylinder swap the plug with one next to it then check again. If the misfire is still in the same place then you know its not a plug.
I doubt you can swap the leads as they will be too short so once you know which cylinder is faulty, follow the lead back to the coil and remove it from there. Start the engine and look into the coil terminal. If the coil is good it will be sparking inside. Do NOT put your fingers there.
Or, with a spark plug from a good cylinder removed, fit it to the lead of the faulty cylinder and crank the engine. There should be a spark on the tip of the plug. If not then swap the lead for another one and try again. If you do get a spark then the lead has failed. If you do not get a spark then the coil has failed.