fiesta idle probs

fiesta idle probs

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impuk

Original Poster:

4 posts

241 months

Saturday 9th October 2004
quotequote all
1.1 CFI unit L reg.

My head hurts ive tried everything i can on this problem. Idle speed is really low and engine cuts out from cold but just manages to hang on when hot. There doesnt appar to be any "choke" operating.
I invested in a halfords diagnosic reader and it comes up with "throttle plate control motor". which i believe to be correct as the DC motor never appears to move or do anything.
I replaced the "throttle plate control motor" with one from a breakers yard but i get exactly the same problem and diagnostic reading.
I then checked for wiring faults by digging a pin in the wires and got voltages on all of the four pins (3v in one and 1.7v in the others including earth !?).

I wonder if anyone knows what the problem might be or can give me details on corect voltages etc
Thanks

nighthawk

1,757 posts

251 months

Sunday 10th October 2004
quotequote all
More likely to be a corrupt reading from the Engine Coolant Temp sensor.
they were the most common thing to cause this fault.

As for the Dc motor, does the throttle pedal move when the ignition is turned off and on when the engine been run up to temp?

might also be worth sticking your multimeter in the Throttle position sensor and checking for out of spec resistances.

impuk

Original Poster:

4 posts

241 months

Sunday 10th October 2004
quotequote all
Thanks ever so much for your advice.

I fitted another throttle position sensor (from breakers)on the offchance but no change in the fault.

I will try to check the coolant temp sensor this week, but it had not shown up as an error on my diagnostic fault finder.

The DC motor/throttle pedal does not move at-all when the ignition is turned off or when up to temp. In fact the Dc motor does not move ever.

I checked the supply voltage at idle to the Dc motor pin and its only 3V. Would 3V be enough to work it ? I suspect it requires 5V or 12V supply but ive no idea why the voltage would be low.



nighthawk

1,757 posts

251 months

Sunday 10th October 2004
quotequote all
The ect never used to throw up a fault code because it was never really faulty.
it had a nasty habit of lying to the PCM,

quite often used to tell the module it was either hotter or colder than it really was, which had a detrimental effect on the fuelling.

Top of my head m8, i can't remember what the voltages were, but i'll check some bits and bobs tomorrow for you

there were loads of TSB's released fpr running issues on the CFi vehicles

impuk

Original Poster:

4 posts

241 months

Monday 11th October 2004
quotequote all
Ive checkd the hot resistance value of the ECT today and its 7.2 Kohms which i guess is ok for about 5 min after ive turned off the engine.

The cold resistance value im going to check in the morning when its near zero degrees... and i should think thats the important one.


impuk

Original Poster:

4 posts

241 months

Tuesday 12th October 2004
quotequote all
Hi checked the ECT resistance values this morning and it seems correct, both cold and hot.
Im starting to wonder if ive been unlucky and the DC motor or TPS i got from the breakers is also faulty.