at current my alternator produces 13.7 volts to the battery, anything between 12v-16v is good, id be a little worried if it was too high.

but my car at the moment when winding down the windows i loose about 100rpm off idle and then it pops back up same with my headlights if do both at the same time the car hits 500rpm and jumps back up quite violently, this is another thing im hoping a new battery will resolve i only had a new alternator fitted last year but is certainly putting the right volts out.

My st does this stason winding windows down etc

My mates focus did it

My old 1.4 mk6 did it (was fun as you could almost get a tune from the exhaust)

Motors will always pull a lot of current and consume power from your engine

Pretty sure they all do it by a very small amount. Make sure your battery acid is topped up!

first chance to try out this new sensor today from a complete cold start. made no difference, i tried giving the engine a chance to breathe without my foot on the throttle to give it a hand and it did then stall so its obviously not that.

back to the garage for a second diagnosis

I'm allao working on it.

Tomorrow i can use the Ford garage the while day. We're closed but i can get in;).

Hope you have some luck, this is beginning to annoy me now.

Hopefully people are reading this, for everyone who's had this problem can you list out your current details so I can show them to the garage.

I'm talking car production year, current mileage, what mods (if any). May help them look for a pattern.

killeruk you've said there's a similar thread going on STOC. can u get similar details from them as well

Cheers

I tried:

- mapping
- sparkplugs
- fuelfilter
- finding error codes (special device)
- tested cam and rock shaft sensor
- tested the innectors

No result.

Whys no one changed a coil pack yet?

i have and did nothing.

different battery nothing

i ordered new spark leads (racing ones). maybe it's that.

i tried a lot. I think it might be a sensor that we're overlooking.

I have the KV85s and it still happens sometimes so I doubt they'll fix it.

I can give it a shot though....

Ok. I need some info for my list. I made a list of all the sensors in the fiesta so i can eliminate them one by one.

- does the car have a bad idle atba cold startup? And after like 10/20 min it's mich better?
- is it worse when it's cold/damp outside?

Please all answer!!

Happens for around 20-30seconds, 15 seconds after start up when its cold. If its been driven ad its sligtly warm or still upto temp it doesnt do it.

Might have found the problem.

Going do test it out today!