Hi all

new to the forum as my Mrs hasn't long had the fiesta. Anyone that can shed any light or help is much appreciated. As above car is Fiesta MK6 1.4 16v 108,000 miles Right...

Only had car since September and all was ok when she bought it but after a couple of months it started cutting out randomly and poor idling. when I say poor idle I mean hunting for an idle but not going up and down to much only by a couple of hundred revs each way but when it goes down it sounds like its going to stall but it doesn't it picks itself back up. but sometimes it does stall and cut out but the only similarities I can see between the cutting out is that the engine is warm and she does a lot of stop/starting or coming up to stop at a junction. sometimes as well it takes a few turns to get it to start after cutting out but it does start. also no fault lights and no dtc's on the dashboard test.

things I have done to try and fix...

new fuel filter

new oil and oil filter

new spark plugs

new air filter (even though it still has the poor idle with the air box off)

cleaned and tested fuel injectors and put the right amount of fuel injector cleaner in the tank

tested fuel pressure regulator. no leaks and done suction test with tube and syringe and the diaphragm is holding

removed throttle body cleaned and replaced

removed map sensor cleaned and replaced

done the old carb cleaner over all fuel and air hose joints to checks for vacuum leaks and couldn't find any

old spark plugs were black as f**k and a little oily so checked after I replaced with new ones a few weeks later and they were really black too. the mrs did say that after I changed the plugs the car was running a lot better for a couple of weeks and then went back to how it was. so its running to rich but after everything I've done im unsure as to why.

Any suggestions or ideas are welcome. im open to anything at this point. it cut out again last night and its to the point where the mrs doesn't even want to drive it.

the only thing im left with yet to try is disconnect the pedal clip and reconnect to check its not loose as the throttle position sensors are in the pedal and throttle body. am I right in thinking that if they were faulty it would bring up a fault light? I've read the fault code list and there are a lot of "intermittent" codes you can get for when sensors are on there way out. but as I said nothing and I know I can just take it for a diagnostics test but id rather try every thing I can do first before I spend hundreds for them to tell me theres nothing wrong with it. might try the old cheapo ones off eBay just to see if there is anything stored.

apologies for the rather long post but im at my wits end. after all I've done it hasn't made the slightest bit of difference apart from the plug change. I would of thought it would of at least got better or worse but no.

Idle control valve.

thanks but the mk6 16v engines don't have one

MK6 Fiestas have electronic throttle? Usually a poor idle only would be the Idle Valve or the throttle cable being knackered. when it's lagging and you give it some throttle does it lag or do the revs pick up as normal?

yeah they have electronic throttle so no cable. yes if you put your foot down revs pick up

Have you taken the TB off and cleaned it? that hinge thing could be sticking? unsure from you said above if you've taken that off and cleaned it or just removed the air hose and filled it with carb cleaner.

Yes throttle body has been off and completely cleaned with carb cleaner and a toothbrush and cotton bud. You could eat your dinner through it if you was inclined

Tested the ignition coil tonight and the secondary windings are in spec but on the primary side im getting 0.6 on one and 1.2 on the other. The spec says it should be between 0.4 and 0.6. Could this be enough to stall the car and give rough idling? Cant hear any misfires though and no fault lights

Fitted new ignition coil and no change

Solved. It was a problem of a worn throttle body and worn ignition coil. Hence not a lot of difference on just changing the coil. Coil 30 new and throttle 20 from breakers

On 18/05/2014 at 8:14 PM, adm88 said:

Solved. It was a problem of a worn throttle body and worn ignition coil. Hence not a lot of difference on just changing the coil. Coil 30 new and throttle 20 from breakers

Hi mate think I'm having the same problem when it is cold and I dip the clutch the revs just keep dropping until it cuts out and stalls. Simular issue? 

On 2/21/2018 at 2:04 AM, Joshallen7478 said:

Hi mate think I'm having the same problem when it is cold and I dip the clutch the revs just keep dropping until it cuts out and stalls. Simular issue? 

Hi. did you manage to solve the issue? Having something similar. Uneven idle when cold but all OK when warmed up.