Hi i would appriciate any help as i have a prob with my st170 thats begining to do my nut in.
I bought the car and shortly after discovered a missfire under load ( high revs mainly ). The problem became really bad and on one occasion has cut out when driving.
I have changed the coil, plugs and ht leads (all oe equipment, but all looked new when removed so i think the problem was already there).
This has improved the problem alittle but i still have it. Mainly on a long motorway journey or when holding the revs in 4th or 5th i get it.

Thanks in advance

 

is the engine standard?

 

Yeah standard any ideas?

 

try an ecu reset, disconect the batterey for 20 minutes, re connect then drive. If if is still doing it it could be a Lambda sensor, Cat, or perhaps fuel pump.

 

Hello Mate,
is the MIL on? I suspect not as you would of mentioned it.
Follow what THOR says and if you get no joy then maybe try a new fuel filter, as enough fuel might be getting through at low revs but not at high revs, which could also indicate an injector.

Another thing you could try, you say your've changed the plugs and HT leads with the same result, so now I would re-gap the plugs smaller, and see if it's any better.
If it's improved somewhat, then you have low voltage at the plugs. (possible coil pack).

Try what THOR suggested then maybe my suggestions.
Best of luck

 

Dose the Engine feel more like its holding back at rev's or like its lost all power? I've had 2 problems with mine, first was the coil pack (engine holding back over 4-5k) and then 6 months later the fuel pump (engine dieing briefly under hard accel over 3-4k)

 

hi yeah its more of a loss of power has been quite violent at high revs.

 

Cheers mate given me something to go on the ecu reset would be a great result if that works. cheers

 

I have change the coil that improved it alot in low rev but now its just top end and when i hold the revs. Will give the above a go.

 

Cheers for all the info, hope i get to the bottom of it as it's spoiling such a great car to drive.
Will let you know.

Thanks brad

 

Sounds like a fuel issue to me, filter and or pump. Happened to me and from what your saying sounds the same. Unfortunately the pumps in the tank and so is a pain to do. Hope it turns out to be something cheaper and easier for you

 

if it is the pump its not too said a job to do, but the tank does have to be dropped at least. not always necessary to completely remove it as ive done a few pumps on normal foci, one thing to consider though is im unsure if the pumps in a shopping spec focus are the same as st170. the st uses a different fuel line setup without a return so i dunno if the pressures are different. BRAINWAVE>>>> PRESSURE REGULATOR ANYONE????????

 

A pressure regulator will put additional strain on the pump, as said your Fuel pump is knackered, very common problem, get it chaged and get an uprated in tank Syntec one, they are less than £200

 

Have driven the car for some distance today and i noticed that the problem incresed as the journey went on it seem ok to start and then gradually got worse and worse until it was almost constantly missing with any amount of pressure on the pedal.
Does this help to diagnose.
cheers

 

I'd say fuel pump too!