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Matt
Matt, Mechanical Engineer
Category: Ford
Satisfied Customers: 21990
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I just bought a 2003 Ford Focus 1.6 with 100k on the clock. Since having it two days i

Resolved Question:

Hi, I just bought a 2003 Ford Focus 1.6 with 100k on the clock. Since having it two days it's starting to have trouble starting cold, where it would take about 10+ seconds to turn over. Car seems to run fine till it gets warm, then the idle will start to judder.
Any help would be very appreciated.
Submitted: 1 year ago.
Category: Ford
Expert:  Matt replied 1 year ago.
Hello this could be incorrect fuelling due to a faulty water temp sensor. If this is the problem then the ECU will be leaving the car constantly ' on choke' and not reducing the fuelling as the engine warms - so unplug the sensor and clean the contacts on both sides with some switch / electrical cleaner (not WD40) and inspect the wiring for any signs of damage to the insulation especially where it runs over other components and through the bulkhead- if this doesn't help consider replacing the sensor as they're not expensive I'd also check for an airleak after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and can lean the engine out and can also allow the engine to rev up when not desired causing rough running.As its a mechanical fault it tends not to turn on the fault light and you can sometimes hear a 'hissing' noise with the engine running. Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts. The best way to locate a leak is to have the engine running and warm and then spray lighter gas /propane around each joint in turn. If the engine rev's up you've found your leak.Now you might think that spraying lighter gas around a hot engine isn’t wise, however the flash /ignition point of gas is about 400°C so you need a naked flame or spark to set it off and I’ve used this method for many years without incident.Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.
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