Adam14

Hi, I have a Mk4 ford fiesta 1999 when the car is hot its absolutely perfect doesnt skip a beat, but in the mornings when its very cold it does strange things...occasionally it will start and then cut out straight away but more often it starts fine and idles fine but when you put any power down or try to move off the revs shot down and it cuts out..i have to leave it running for 10 mins or so to get it warm then its fine. I have changed the idle valve to a brand new one and taken off the throttle position sensor and cleaned it and checked the wiring for any damage but seems fine. It only ever does it when its a cold day or its raining..if theres any sun on it its perfect..any suggestions? Thanks

R.S.LOGAN

Replace engine coolant temp sensor .This lets the ECU know how much fuel to supply i.e more fuel on cold start (like old car choke ) Easy and cheap to replace .

Adam14

Ok will try that thanks!

R.S.LOGAN

Take it the plugs are o.k and not due replacing ? Dirt round about them can cause spark to track which wont help either .Likewise ignition coil .

Adam14

yeah the plugs were changed about 2 months ago so should be fine, will check them though

Adam14

Changed the coolant temp sensor and it seems to start fine in the morning now! Great! but its still doing a few weird things like when its cold at certain revs i suddenly lose power until i take my foot of the accelerator and go again, does it in all gears when cold but only 5th when its warm!

Also when u just put a slight bit of pressure on the accelerator the revs go straight down and tries to cut out..but if u put any more pressure down then it revs up fine? any suggestions what this could be? thinking of maybe changing the throttle position sensor next?

When i go through big puddles at speed too it just cuts out and acts as if theres no fuel getting to the engine it wont then start properly for another 10 mins...i have changed the fuel filter but had no effect..so put a black plastic bag over the fuel filter and it seemed to have stopped it...any ideas though on a more permanent solution? Any help would be much appreciated thanks!

R.S.LOGAN

Try changing plug leads , may be breaking down under load .Also check coil is clean and try otherwise can cause tracking of spark . Dont know how putting bag over fuel filter would cure that fault .Dont go through big puddles AT SPEED , slow down .Going through at speed soaks electrics causing the fault you describe .You want to go fast on water , get a boat .

Adam14

ok thanks will give it a go! Well i dont mean speed i mean more than 5 mph haha i have to crawl through puddles for it not to cut out, any more than that it does it!

fordfan21

I had that problem and I just waited a bit longer to start up the engine before I went on my way.

Link removed .

R.S.LOGAN

Shouldn't have to wait before you can drive off if car operating o.k.