Ford Focus MK1 1.8 Low Idle Causing To Stall

[GBTurbo]

Hi I wondered if anyone could help I'm starting to draw a blank with trying to fix this car.

Its a Ford Focus MK1 1.8 Petrol black top zetec, its developed a really low idle and it now stalling the car when cold.

The idle full stop is really low, when hot/cold/medium its always really low but now due to the colder weather the car will stall unless you give it a few revs. A bit of a pain trying to pull out on junctions etc from cold.

When the car is started its like its not getting any signal that the car is cold and to adjust the air/fuel mix.

I had an old clio that was really difficult to start in the cold and that turned out to be the coolant temperature sensor. I've read up on the focus and it has a cylinder head temperature sensor instead but the same principle.

Checked for vaccum leaks and can't find any, I've had the idle speed control valve out cleaned it and measured the resistance and everything is within tolerance, plugs and leads seam good, if I disconnect the maf when the car is running it runs weird and stalls (so I can maybe assume that is working) I haven't tested the throttle position sensor yet but doesn't seam dead.

Scanned for codes can't find any and checked the dash for DTC codes and there isn't any.

I measured the input plug to the temp sensor and it had 4.5v when ignition on, I can't get a measurement of anything back from the sensor itself, but I'm not 100% sure what I'm looking for, maybe a resistance (ohms) but I'm unsure.

If I disconnect the plug and start the car it behaves in exactly the same way so am I right in saying the sensor is dead?

The reason I haven't bought another sensor yet is the car is a shed (<£500) and I don't see the point of randomly changing sensors for no logical sense.

Anyway, sorry for the long post if anybody has any tips/input that would be very helpful

Cheers

Used this site for reference

http://www.gomog.com/allmorgan/ZetecIdleIssue.htm

[ch427]

check the resistance across the 2 terminals of the CHT sensor at various temperatures, autodata suggests
@ 20 degrees it should be approx 34000 ohms
@ 85-90 degrees should be approx 1300 ohms
Should be a gradual decrease in resistance as temperature goes up.
Ive guessed your car is a 2000 model but it should be the same

[GBTurbo]

Hi thanks for the reply,

I went outside and had a quick check I got 52000 ohms at the sensor. I'd say its about 4-5 degress outside so I guess that figure is correct? With the hotter it gets the lower the resistance.

I will check when I take the car for a run tomorrow but maybe that sensor is working...!

Anything else I should check?

Much appreciated, cheers

Sorry forgot to add yeah its a 1998 but should be exactly the same as you say.

[ch427]

Throttle pot and idle valve problems are very common on most fords of this type, not actually done any on a focus but i would expect the idle circuit maybe the culprit here

[GBTurbo]

Will check the throttle pot tonight I did read of one guy who had a small dead spot in the throttle pot and that was the problem, is it worth buying a new idle control valve even though this one is within spec?

I found another guy who found the vehicle speed sensor to be duff causing a rough idle but I haven't had any other of the related problems (dead speedo trip counter resetting etc) but again Haynes doesn't give you any values.

Is autodata a trade thing better than the Haynes?

Cheers

[ch427]

The closed throttle signal is usually where it gets out of range. if you cant access the terminals then cut back the insulation slightly to expose the copper using a sharp knife, you can test with the ignition on. Just be carefull not to short or cut through the wire!
Voltage change should be smooth throughout the throttle range, try not to disconnect the throttle pot with the ignition on.

Terminal 3 to earth should have 5 volts on it with ignition on
Terminals 1&2 throttle closed 0.8 volts approx
Terminals 1&2 throttle fully open 4.5 volts approx

[GBTurbo]

Thanks for that I will give it a try when I get in.

Edited by GBTurbo on Thursday 21st November 15:19

[GBTurbo]

I didn't cut the wires to the sensor yet I tried to check the resistance of it, according to haynes it should be 400-6000ohms with a smooth sweep across, I couldn't get it to read anything..?

I've got 5v coming in I checked that.

I made a little video today of how it behaves

https://www.dropbox.com/s/3jfpmrjrrwk48pp/Video%20...

The vibration noise is some coins in the dash pocket, not a knocking engine! It does vibrate quite bad at the low idle though.

1st and 2nd attempt are starting with no throttle 3rd is with my foot lightly on the throttle.

Then I let my foot completely off the throttle and it idles but really low, and then a blipped it a few times and it eventually stalls.

Throttle pot is £9.95 so maybe this one is dead at the closed throttle end as you mentioned, I am a little reluctant to cut the wires to test the voltages, but I don't want to waste even £10 on the car if I can help it.

Cheers

[ch427]

No need to cut any wires, if you can't get your meter in to test the terminals you just pierce the insulation to expose the copper.

[LordLoveLength]

ch427 said:

No need to cut any wires, if you can't get your meter in to test the terminals you just pierce the insulation to expose the copper.

Or, if you can get to the connector, you can carefully push pins down the side of the wire into the connector itself. Use the pins with the round plastic heads.

[GBTurbo]

Managed to just nip the insulation and balanced the leads carefully and checked the throttle pot, got the values you mentioned

0.8v closed and 4.5v when fully open.

Very carefully went through the range a few times and the voltage increases/decreases smoothly with no spikes or dead spots that I can find.

Throttle position sensor working I take it.

At least my multimeter is getting a workout!

Any suggestions keep them coming.

Many thanks

[Jaz7646]

If the 1.8 is the same layout as the 1.6, check the PCV hose that sits behind the manifold at the front of the engine. Just had to replace this on ours due to dodgy idle. Basically when the engine is running the pressure was causing this hose to collapse - as the hose gets very hot, it gets spongey over the years.

Worth a check.

[GBTurbo]

Does the hose run under the exhaust manifold?

The 1.8 layout has the inlet manifold at the back and the exhaust manifold at the front near the bumper.

Will check tomorrow thanks

[GBTurbo]

Had a look today found the pcv valve checked the pipe work and looks to be in good condition. Used an inspection mirror to check the underneath an no splits.

Took it for a drive this afternoon drives fine it's just starting from cold which is the problem.

[GBTurbo]

Never did get to the end of this problem, sold the car cheaply and told the guy what was wrong.

Cheers to all that helped