Hello I wondered if anybody could help or has experience with a similar issue to what I'm having.

 

I have a 2019 st line 140ps model with 20,000 miles covered which I've owned for a few weeks, it had it's first service after 2 years and because I started to get this issue I went ahead and had it serviced early including spark plugs so I could rule those out but it's still doing it.

 

I'm getting some mild surging between 2000-3500rpm, it happens in most of the gears but only in that range from what I can tell. It only happens when the engine is warmed up and it's intermittent too, shorter trips it doesn't do it but on longer runs it eventually starts. I can hold my foot steady at say 2500rpm in 3rd gear and it starts micro surging, as if the boost is coming in and then going out straight away, it's kinda hard to explain. Same on the motorway, I can be in 5th/6th gear same revs holding my foot steady and it starts doing these little surges like pulsing. I've had a few fill ups now and used shell ultimate fuel each time.

 

It's been back to the dealer today and they've had it on the diagnostic machine and test driven it, but they've told me they can't see anything wrong. I'm going back down tomorrow so I can drive it with the technician in the hope it does it while I'm there but has anybody got any ideas on what it could be?

 

I've owned many fiestas over the years, mk7 st before this and it never did anything like this, it's not lag on the boost, it's what I would describe as a surge or pulse

 

cheers

Did you ever get to the bottom of this? Mine is same year and model but mines mapped with revo and getting same surge on boost in same range when holding foot steady on the peddle. if i drive slowly its fine, if i hammer it its fine as well. Got a boost pressure sensor coming today hopefully thats the issue. No engine codes.

42 minutes ago, a7mag3ddon said:

Did you ever get to the bottom of this?

Who knows. @Wizzybob only ever made one post.

Vacuum pump one way valve??????

8 hours ago, DaveT70 said:

Vacuum pump one way valve??????

How can I check this? Anyway to look at live data. Ive checked boost pressure using live data check and can see it boosting them pulling back so definitely a problem somewhere. Also checked all the air pipes etc for leaks and tightened clips up.

 

Undo the pipe to the vacuum pump and see if the one way valve has collapsed

Cheers I will, wouldn't that cause it all the time though? When I floor it or drive it steady it doesn't do it and dumps air normally.

If I don't reply I'm not ignoring, I don't get notifications of replys, I've just changed the email on the account to see if that works and verified it.

I've been out and checked, I've got a vacuum on it I can put my finger over the black nozzle and it sucks it I assume that's ok ?

I've read about the split orange diaphragm and I've whipped my valve out, looks perfect, no tares, rips, holes or anything. Looks brand new.

Still having this surge issues, checked pipes for leaks, checked valves, any other ideas? Local garage said it could diagnose using live data but what wkare they checking ??

I doubt its the problem but it sounds similar to what I had, is your air con low on gas? Mine was low on gas and it had very similar symptoms to yours. I had it re-gassed and it solved the problem. Try driving with the air con off and see if the surge occurs, worth a try to rule that out I suppose.

Air con is fully gassed and does it with it on or off. Still having the problem its bizarre.  Might just have to pay a garage to look at it, only does this when accelerator pedal is half on when on an inclined. all the rest of the time its fine.

Still got this issue if there's any fresh eyes on this post