Ford Fiesta ST
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#562787 - 10/10/18 11:32 PM Bucking/Jerking
Seannymr200 Offline
n00b

Registered: 10/10/18
Posts: 5
Hi all

Having an issue with my MR200 ST with as the title says, bucking and jerking. This happens when I let my foot off the accelerator. It is most noticeable at low engine RPM in 1st and 2nd. Less so in the higher gears at higher speeds but still noticeable. I canít crawl along in traffic without constantly dipping the clutch to prevent it looking like Iím a learner on my first lesson lol my engine was recently rebuilt after the crank had to be repaired and a couple of rods replaced along with various other internals. Previous to this I had to have my gearbox repaired but that was about 3 years ago and I had no issues after this. Throttle body is lovely and clean, I have no exhaust leaks (not that I could find). Iíve also tried resetting the KAM just in case it was a TB issue by removing fuses then leaving out for a while and then idling the engine for 10 minutes and then taking it for a short gentle drive. Iím thinking could it be a vacuum leak? Could it be engine mounts? Could it be something far more sinister (hope not). Or maybe a fuel delivery problem with the pump? Spark plugs were changed around 4000 miles ago. When the engine was repaired the battery would have been disconnected for a fair while would this have somehow affected the ECU at all?? Only other things Iím aware of are a quiet whining noise that starts just after the engine has found its idle point which increase with engine RPM. It also becomes more noticeable when I put things on like heated seats and the window/mirror heaters so maybe something to do with the alternator. The whining isnít the PAS. I had this replaced in January and the fluid is still pink and makes no noises when I turn the wheel. Plus I know what a bad one of them sounds like from previous repairs!

Any advice or info anyone could give me would be much appreciated.
Many thanks
_________________________
56í Fiesta ST
MR200 @ WR Davies
Black ST 500 Alloys

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#562788 - 10/10/18 11:42 PM Re: Bucking/Jerking [Re: Seannymr200]
_Jimmy_ Offline
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Registered: 11/02/14
Posts: 1226
Loc: Northwest
Mine has always been jerky when cold, once it's warm it eases.
Could it just be the sportier cams making it jerky at low speeds? Mine is a little bit troublesome in traffic.
_________________________
2005 Fiesta ST
Milltek non-res, Newman fast road cams, Fusion Fabs custom inlet manifold

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#562790 - 11/10/18 07:10 AM Re: Bucking/Jerking [Re: Seannymr200]
Seannymr200 Offline
n00b

Registered: 10/10/18
Posts: 5
Hi
Thankyou for your reply. I donít know whether it would or not. It doesnít matter if itís hot or cold it still does it. I had the MR200 conversion done in 2013 and it didnít behave like this then and Iíve had no other mods. Like most people, I am dubious about taking it to my local Ford dealer and explaining it to them for them to come back and say I need a new car or something lol
_________________________
56í Fiesta ST
MR200 @ WR Davies
Black ST 500 Alloys

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#562794 - 15/10/18 01:41 PM Re: Bucking/Jerking [Re: Seannymr200]
YellowBadge Offline
MountooningTipster

Registered: 26/08/07
Posts: 11393
Loc: here
you can't crawl in traffic with MR200 anyway, prob need around min 10mph in 2nd otherwise the cams won't be happy. But sounds like after your rebuild it's worse, so I would look at that, timing perhaps needs checking, maybe get it on a rolling road and see what the data gives back fuel air etc.
_________________________

MR200 Stage 3 200PS
Evans Halshaw
Mountune Pro

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#562795 - 18/10/18 06:35 PM Re: Bucking/Jerking [Re: Seannymr200]
Seannymr200 Offline
n00b

Registered: 10/10/18
Posts: 5
I never used to have any issues with it in traffic before. Sure it would nearly go to stall when too low an engine speed in too lower gear. What about PCV hose? Bugger to get to though unless anyone has any tips to get to it without removing the inlet manifold!
_________________________
56í Fiesta ST
MR200 @ WR Davies
Black ST 500 Alloys

Top
#562805 - 21/10/18 12:28 AM Re: Bucking/Jerking [Re: Seannymr200]
_Jimmy_ Offline
Site Supporter

Registered: 11/02/14
Posts: 1226
Loc: Northwest
Maybe, a split PCV hose usually causes a high idle speed as well. You might be able to get to the hose behind your inlet if there is some access, will be fiddly though. You could check for vacuum leaks by spraying water from a trigger spray and see if it alters the running.

I just found today that one of my inlet bolts had worked loose but then it was making a noticeable high pitched whistling noise at idle, was also getting rev hang when pulling to a stop.
_________________________
2005 Fiesta ST
Milltek non-res, Newman fast road cams, Fusion Fabs custom inlet manifold

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#562820 - 23/10/18 09:46 AM Re: Bucking/Jerking [Re: Seannymr200]
MarkThe Shark Offline
n00b

Registered: 18/07/18
Posts: 22
Loc: Leeds
I would use carb cleaner over a water spray but definitely worth checking all vacuum pipes.
A cheap ebay scan tool and the torque app would be helpful for you.

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#562828 - 23/10/18 06:37 PM Re: Bucking/Jerking [Re: Seannymr200]
_Jimmy_ Offline
Site Supporter

Registered: 11/02/14
Posts: 1226
Loc: Northwest
I just thought carb cleaner is a bit volatile but if you're careful it should be ok. It dissolved the top layer of plastic on my headlight!
_________________________
2005 Fiesta ST
Milltek non-res, Newman fast road cams, Fusion Fabs custom inlet manifold

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#562839 - 24/10/18 12:11 PM Re: Bucking/Jerking [Re: Seannymr200]
Seannymr200 Offline
n00b

Registered: 10/10/18
Posts: 5
Thankyou for your replies. Sorry I donít get to check on here all that often. I will get it up on the Ramps and see if I can see the PCV valve and hose from underneath. The whining noise I hear is weird because it doesnít start until about 2 seconds after the engine has cranked and then gets higher in pitch with the revs but it also seems to get worse when I stick heated seats mirrors and screens on. Alternator going bad??
_________________________
56í Fiesta ST
MR200 @ WR Davies
Black ST 500 Alloys

Top
#562840 - 24/10/18 01:38 PM Re: Bucking/Jerking [Re: Seannymr200]
_Jimmy_ Offline
Site Supporter

Registered: 11/02/14
Posts: 1226
Loc: Northwest
Not sure if you can see the hose better from underneath but I have access to mine from above, the PCV is the orange thing you can see here between the inlet runners

_________________________
2005 Fiesta ST
Milltek non-res, Newman fast road cams, Fusion Fabs custom inlet manifold

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#562841 - 24/10/18 02:43 PM Re: Bucking/Jerking [Re: Seannymr200]
MarkThe Shark Offline
n00b

Registered: 18/07/18
Posts: 22
Loc: Leeds
Nice intake man what is it? and what's with the dodgy fuel rail connector? I have the same ramair too.

Yeah standard manifold will need to come off to get to the pcv pipe. sometimes they aren't even leaking but they get soft and collapse under vacuum. Roose motorsport sells an upgrade pipe for 20 quid.


Edited by MarkThe Shark (24/10/18 02:44 PM)

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#562842 - 24/10/18 08:34 PM Re: Bucking/Jerking [Re: Seannymr200]
Seannymr200 Offline
n00b

Registered: 10/10/18
Posts: 5
Hi

Yeah I found it earlier and the hose coming off it looks fine. I suppose it could be clogged inside?? I think I can hear a hissing noise on the left side of the engine almost same level as the pcv valve with a similar hose nearby but Iím not sure. I connected my car to a diagnostic app with an OBD port connector and at roughly 1000rpm idle the throttle position says itís 13.7%. Does anyone know if that sounds right?? Oh and how do you put pictures on??!
_________________________
56í Fiesta ST
MR200 @ WR Davies
Black ST 500 Alloys

Top
#562845 - 24/10/18 09:58 PM Re: Bucking/Jerking [Re: Seannymr200]
YellowBadge Offline
MountooningTipster

Registered: 26/08/07
Posts: 11393
Loc: here
what is a PCV and is it only on older cars ? Can't see any orange thingy on my 2007
_________________________

MR200 Stage 3 200PS
Evans Halshaw
Mountune Pro

Top
#562846 - 24/10/18 10:05 PM Re: Bucking/Jerking [Re: MarkThe Shark]
YellowBadge Offline
MountooningTipster

Registered: 26/08/07
Posts: 11393
Loc: here
Originally Posted By: MarkThe Shark
Nice intake man what is it? and what's with the dodgy fuel rail connector? I have the same ramair too.

Yeah standard manifold will need to come off to get to the pcv pipe. sometimes they aren't even leaking but they get soft and collapse under vacuum. Roose motorsport sells an upgrade pipe for 20 quid.



It's an FF custom made to order for the 2.0L engine, really only this and the now unavailable Mountune IE4 inlet the only ones specific to the 2.0 engine. Others are available like the Cosworth one and there is another out there.
_________________________

MR200 Stage 3 200PS
Evans Halshaw
Mountune Pro

Top
#562850 - 25/10/18 11:38 AM Re: Bucking/Jerking [Re: MarkThe Shark]
_Jimmy_ Offline
Site Supporter

Registered: 11/02/14
Posts: 1226
Loc: Northwest
They've all got a PCV, it's the crankcase vent.
If the hose looks OK it shouldn't be causing a vacuum leak.
Might be worth checking the inlet manifold bolts if it's been removed, they don't need a lot of torque, just 18Nm.

Originally Posted By: MarkThe Shark
Nice intake man what is it? and what's with the dodgy fuel rail connector?


Yeah, as said above it's a Fusion Fabrications cutom one, tried to acheive similar performance to the mountune one torque wise, gives a nice sound too. Dodgy pipe is the result of my clumsy spanner use, originally used hose just to get it running but it's just stayed like that since.

_________________________
2005 Fiesta ST
Milltek non-res, Newman fast road cams, Fusion Fabs custom inlet manifold

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