ford focus mk1 1.6 lx

[Matt N]

Hi, I`m hoping I can get some help, I have a 2004 mk1 ford focus petrol, every time I come to slow down my engine revs drop and nearly cut out, its now started to tick over lumpy now aswell and its doing my head in. I've been told it could be the idle control valve or the maf sensor. If anyone could help me out with how to test these problems or anything else that could be causing it, I would much appreciate it. thanks.

[Tdci-Peter]

5 hours ago, Matt N said:

every time I come to slow down my engine revs drop and nearly cut out, its now started to tick over lumpy now aswell and its doing my head in. I've been told it could be the idle control valve or the maf sensor

If you do not have a code scanner, I strongly advise getting one. Basic ones like the U480 start from under £10. There can be codes without the EML on, and the MAF test below is likely to cause a code (& EML on) which you need to read & clear.

Then you need to check if the car has a MAP or a MAF. The MAF is usually in the air duct just after the air filter box. The MAP would be a smaller item in the inlet manifold somewhere. Sellers give both as fitting your car, but for most petrol engines, it is one or the other.

Simply disconnecting the MAF can help diagnose some MAF problems: If it cures the idle problem (though it may cause limited power mode or the EML on), then MAF is a strong suspect. The same trick might just work with the MAP.

It is possible the car has an electric throttle body, rather than bowden cable operated. In that case there will be no Idle valve, the ECU uses the throttle body for idle. But either of these units can stick due to wear or dirt, or have electrical connection problems.

Less likely suspects include the O2 sensor(s), and exhaust system leaks (before the O2 sensor, allowing air into the exhaust).

For picture of MAP sensor: http://www.ebay.co.uk/itm/Ford-Focus-MK1-1-6-16V-Genuine-Lemark-MAP-Sensor-OE-Quality-Replacement-/361507885027

[v530anh]

You can take the piping and air filter panel off in 5 minutes. Then just take it inside the house, much easier than you will need torx set, and comma contact spray to clean the sensor. Then just put it back in your car.

Though putting a new ignition coil had a direct effect on my idle revs. Though best to get a good coil not a cheap one.

[Matt N]

On 11/24/2016 at 1:17 AM, Tdci-Peter said:

If you do not have a code scanner, I strongly advise getting one. Basic ones like the U480 start from under £10. There can be codes without the EML on, and the MAF test below is likely to cause a code (& EML on) which you need to read & clear.

Then you need to check if the car has a MAP or a MAF. The MAF is usually in the air duct just after the air filter box. The MAP would be a smaller item in the inlet manifold somewhere. Sellers give both as fitting your car, but for most petrol engines, it is one or the other.

Simply disconnecting the MAF can help diagnose some MAF problems: If it cures the idle problem (though it may cause limited power mode or the EML on), then MAF is a strong suspect. The same trick might just work with the MAP.

It is possible the car has an electric throttle body, rather than bowden cable operated. In that case there will be no Idle valve, the ECU uses the throttle body for idle. But either of these units can stick due to wear or dirt, or have electrical connection problems.

Less likely suspects include the O2 sensor(s), and exhaust system leaks (before the O2 sensor, allowing air into the exhaust).

For picture of MAP sensor: http://www.ebay.co.uk/itm/Ford-Focus-MK1-1-6-16V-Genuine-Lemark-MAP-Sensor-OE-Quality-Replacement-/361507885027

I have disconnected the plug off the map sensor and it runs perfect. so assuming its the map sensor will get that changed soon. have you got any idea how easy they are to change? looks like the inlet manifold has to come off.

[Tdci-Peter]

38 minutes ago, Matt N said:

I have disconnected the plug off the map sensor and it runs perfect. so assuming its the map sensor

There are lots of causes for rough running, but not many of them would vanish if the map was unplugged. I guess without the map, the ecu has to make a very rough guess of the air flow into the engine, and set the fuel & ignition timing to that. So vacuum leaks and related problems would still be problems. I might monitor it first with a diagnostic tool, or backprobe the connector to read the output signal. But it could be easier to just remove & replace it.

Is this photo anything like the right engine? (the writing on the photo is wrong, should be MAP) If so, I can see it will be awkward. Someone said the alternator had to be moved. Also some said the sensing tube can get blocked.