1.8tdci Focus Idle Misfire
Discussion
After writing a post on nearly every ford forum with 0 replies, I am hoping the clever people on here may help 
Having some difficulty trying to find the fault that's causing a misfire/hunting on my 2006 focus tdci 1.8 (engine KKDA)
When started from cold the engine idles fine with no apparent fault and drives as normal, however as soon as the engine reaches full temp its like a switch and all of a sudden the engine struggles to the point its as if its only running on 2 cylinders.
If I were to rev it, it would rev normal and drive normal.....but as soon as the idle starts to stabilize it just drops and start hunting.
I have changed all 4 injectors
Replaced Fuel Filter
Carried out full service (air/oil filters and glow plugs)
Blocked the EGR valve
Checked all connections to major sensors
Im Using Forscan and I have a fuel pressure reading between 295 - 305Bar Map and Maf are reading within range and coolant temp and air temp appear to be within the correct ranges aswel.
Things appear to run ok for a couple of hours when messing about with the fuel side of things eg: injectors and fuel rail etc but no matter what I do the poor idle returns.
Driving seems to be Ok however there is a noticeable vibration through the rev range.
I am hoping that there may be someone that could help me out and maybe give some pointers as to what else I could be looking at, I did not want to start changing random sensors in the hope that it may fix it.
Having some difficulty trying to find the fault that's causing a misfire/hunting on my 2006 focus tdci 1.8 (engine KKDA)
When started from cold the engine idles fine with no apparent fault and drives as normal, however as soon as the engine reaches full temp its like a switch and all of a sudden the engine struggles to the point its as if its only running on 2 cylinders.
If I were to rev it, it would rev normal and drive normal.....but as soon as the idle starts to stabilize it just drops and start hunting.
I have changed all 4 injectors
Replaced Fuel Filter
Carried out full service (air/oil filters and glow plugs)
Blocked the EGR valve
Checked all connections to major sensors
Im Using Forscan and I have a fuel pressure reading between 295 - 305Bar Map and Maf are reading within range and coolant temp and air temp appear to be within the correct ranges aswel.
Things appear to run ok for a couple of hours when messing about with the fuel side of things eg: injectors and fuel rail etc but no matter what I do the poor idle returns.
Driving seems to be Ok however there is a noticeable vibration through the rev range.
I am hoping that there may be someone that could help me out and maybe give some pointers as to what else I could be looking at, I did not want to start changing random sensors in the hope that it may fix it.
I have no experience with that engine or that type of problem, so take this as speculation rather than advice.
Given how abruptly the problem starts, I wonder whether the problem is caused by the engine management system changing behaviour when it thinks the engine is up to normal temperature.
If that was me, I'd look for the engine coolant temp sensor and see what type it is. Most likely it is a thermistor. If so, you can replace it with a variable resistor with the appropriate range, get the engine up to temperature and see whether the problem is affected by changes in the CTS reading. This still doesn't tell you what the problem is, but if you can make the problem come and go at will by tweaking the CTS reading that's got to be a big help tracking down what's changing when the problem happens.
Given how abruptly the problem starts, I wonder whether the problem is caused by the engine management system changing behaviour when it thinks the engine is up to normal temperature.
If that was me, I'd look for the engine coolant temp sensor and see what type it is. Most likely it is a thermistor. If so, you can replace it with a variable resistor with the appropriate range, get the engine up to temperature and see whether the problem is affected by changes in the CTS reading. This still doesn't tell you what the problem is, but if you can make the problem come and go at will by tweaking the CTS reading that's got to be a big help tracking down what's changing when the problem happens.
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