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2008 Focus Undetectable Intermittent Starting Problem

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Info on the problem.


- 2008 Ford Focus 1.6 Style
- Auto
- 30,000 Miles


Short version of what’s wrong with the car and important notes:

- Mostly heat related starting problem

- The car drives perfectly

- There is no injector pulse when fault is occurring, the most important info here is wiggling the wiring harness WILL get the car to start when the car is NOT hot, however when the engine has warmed to normal operating temp wiggling wires will not have any affect which I’m guessing is due to thermal expansion.

- ECU has been swapped out with another new one and problem persisted.

- Disconnecting the ECT sensor will get the car to start almost 99% reliably.

- ECT sensor has been replaced.

- Crank sensor has been replaced.

- No fault codes ever registered.


I have been trying to trace the problem through the wiring harness but it’s proven to be too difficult.

The current process I’m using to find the problem is to investigate all sensors and their circuits that have anything to do with fuel injection, the only problem is that I do not have a large knowledge base when it comes to cars.

I am wondering if you guys can help me and please be so kind to tell me what sensors you know to affect fuel injection and if you’ve ever heard of such a problem before or know of anything that could help.

I have a scanning tool and have been inspecting how certain sensors work and everything seems to be fine (voltages .etc) to my knowledge which again isn’t vast.

I have had a friend bridge the whole ECT sensor circuit to eliminate it and sure enough the problem is not regarding the ECT circuit.

I’m getting close to having to give up a perfectly good car all because of some stupid wiring problem.

Thank you for any help, it is much appreciated.


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