Hi all,

Does anybody have any idea why my mk7 fiesta stalls when slowing done at lights or slowing to turn ect? Unless I rev the car the needle just drops and cuts the engine out. I want to try and clean the egr valve but no idea where it is, any ideas? On 1.25L 2010 fiesta. 

Cheers in advance. 

Hi,

This engine doesn't have an EGR valve, so we can rule that out.

The most likely cause on this engine is a vacuum leak around the inlet.  Often this is caused by a split in the rubber PCV hose under the plastic inlet.

Ohh OK thanks for that I'll check this tomorrow.. I've also replaced the throttle body on it which I believe also has an integrated throttle position sensor so I can also rule those two out as that didn't improve anything. Everything ive read has pointed towards a vacuum leak so I'll look into this more. Car drives absolutely fine once it's had a few moments of wanting to stall at stops, with no codes or dash lights. 

Have you got a odb fault code reader? If the car is fine once it's warmed up I'd check the temperature sensor. Most readers with live data you can see what temperature the sensor is reading from cold and as it warms up. Failing that as above, a vacuum leak on the inlet side

The 2.0 duratec in the mk3 mondeos were nototrious for this, the rubber vacuum pipe right in the middle of the inlet manifold would split where it pushes on to the fitting. 

 

bit of a pain to get into if you have shovel size hands. 

Hi, do you mean the pvc hose that sits under the manifold? I've had that out and the valve itself, valve rattles when i shake it suggesting its not stuck in my mind and the small piece of hose all looks fine. 

I'm going to check temp sensor tomorrow I think to see what that says on the live data, is it easy enough to replace the manifold gasket on a fiesta? I'm quite happy getting stuck in to bits on a car but does it require any specialist tools or just removing hoses, connections and torx bolts? 

If the vacuum hoses are fine then I would check the temp sensor next. It should be reading around an ambient temp on start up from cold and obviously increase as the engine warms up. I had a similar fault with 1.6 focus, wouldn't idle properly and tried cutting out at junctions. It was fine when the engine was up to working temp though.

The sensor was dead and it was reading over 70c regardless if the engine was cold or hot. Is your car only playing up when it's cold or also when the engine is hot?

Basically the ecu thought the engine was hot and was not giving enough fuel to to warm it up properly. Like not pulling the choke out from cold on the old engines (pre 90's). Symptoms even worse in cold weather.