ST170 - Variable Value Timing problem?

[HeavySoul]

Afternoon,

Having a bit of a nightmare with my ST170 engine at the moment - hope someone can push me in the right direction..

Basically after being used for about a good while, the engine has real trouble pulling/accelerating once it goes beyond 3000rpms and struggles badly until nearly cutting out about 5000rpms. It starts to kangeroo down the road upon any type of decent acceleration and once this has started it gets worse. As my journey continues, I can barely push the throttle in, meaning a recent long journey to Wales became extremely tedious and also somewhat dangerous in overtaking situations.

Someone has suggested that this may be to do with the Variable Valve Timing on the ST170 engine but surely this would mean the car would struggle with this from cold? If I use the car in the morning, it will be perfectly fine but it's only once the engine is properly heated up and used for prolonged periods that this starts to happen. Seems maybe something is expanding with the heat to cause this?

The car recently ran dry on fuel because the fuel card in the tank appears to be shot and took the RAC man a lot of fiddling under the bonnet before he found this out to be the cause of not starting. This problem has only started after this event which seems a strange coinicidence

I initially thought maybe the scum from the bottom of the petrol tank had causd the engine to not run properly but have been informed that most modern cars have pipes in the tanks to stop this happening these days anyway. I have run high octane fuel and Redex through the tank to help clear any potential blockages but this is still occuring

Could the RAC man of knocked something in the engine that would cause this maybe?

Anyone have any similar experiences or advice with this? Any help would be appreciated greatly as I am missing the full use of her power

Edited to clear some things up

Edited by HeavySoul on Monday 4th February 15:30

[Damian S]

I had something similar to this in an old audi, although the symptoms werent quite as extreme. turned out to be a knackered throttle position sensor.

if the problem was in the fuel system then I would have thought it would be present all the time. As it appears to be more heat related I would guess that its a failing sensor causing the problem.

[Evilbat]

Have you checked that the Dual Stage Inlet Manifold is working properly ?
At position II on the ignition you should hear the servo switch over to change over to the "long" runner for low revs. Will be handy to use a mate here with bonnet open. The servo is the alloy rectangular box fitted to the bulkhead. If it isn't operating then it'll be a replacement. If it is operating then the other cause may well be a broken pin on the DSIM cam. These are plastic and have been known to break. Ford now do an upgrade. The cam can be seen by looking down the gap between the throttle body and the cylinder head. As the servo operates at position II, you should see it switch over.

If the above are all working correctly, then the next option would be to check the ignition coil pack and spark plugs.

[HeavySoul]

Cheers for the replies chaps I will look into both of those.

If anyone has any more ideas/experiences then please keep them coming

ETA...
Evilbat are you on FFOC? From looking at the dashboard on your profile it would be in keeping with the external looks of a certain black Focus

Edited by HeavySoul on Wednesday 6th February 14:07

Edited by HeavySoul on Wednesday 6th February 14:10

[Zad]

It always amuses me that people think that fuel is only collected from the bottom of the tank when it is running low! Fuel is always collected from the lowest part of the tank, therefore silt and gunge get removed continually. This is not to say there isn't a fault with the fuelling though. It may be that the fuel pressure is too low and it is running super lean when at speed. With a turbo that could ruin the engine in no time.

I would just get it plugged in to an analyser and get any fault codes read out. That should point you to any faulty sensors etc.

[HeavySoul]

Zad said:

It always amuses me that people think that fuel is only collected from the bottom of the tank when it is running low! Fuel is always collected from the lowest part of the tank, therefore silt and gunge get removed continually. This is not to say there isn't a fault with the fuelling though. It may be that the fuel pressure is too low and it is running super lean when at speed. With a turbo that could ruin the engine in no time.

I would just get it plugged in to an analyser and get any fault codes read out. That should point you to any faulty sensors etc.

Had it plugged in this afternoon and no fault codes were thrown up. My garage man said because there were no engine management lights on the dash it would be hard to diagnose what's wrong with the car as it doesn't think anything is wrong necessarily...

[dickkark]

I`ve changed a few fuel pressure regulators on ST 170`s.
Unfortunately they come on a new fuel rail and cost about £80.
they often dont trigger a fault code and give symptoms similar to your description.
HTH

[Evilbat]

HeavySoul said:

Cheers for the replies chaps I will look into both of those.

If anyone has any more ideas/experiences then please keep them coming

ETA...
Evilbat are you on FFOC? From looking at the dashboard on your profile it would be in keeping with the external looks of a certain black Focus

Funnily enough, yes, and with the same username !!

[HeavySoul]

dickkark said:

I`ve changed a few fuel pressure regulators on ST 170`s.
Unfortunately they come on a new fuel rail and cost about £80.
they often dont trigger a fault code and give symptoms similar to your description.
HTH

Dick - thanks for your help - seems to be the most likely cause I think, especially if this triggers similar symptoms like you say..

Ford quoted a price of £109 + VAT this morning...
Roughly how many hours work is this to replace, just thinking of labour costs?

Don't need any work do you?!

[Podie]

I don't know enough about the ST170 lump to *know* but with those sypmtoms on a Duratec V6 I'd look at changing the IRMC.

[HeavySoul]

Podie said:

I don't know enough about the ST170 lump to *know* but with those sypmtoms on a Duratec V6 I'd look at changing the IRMC.

[Podie]

HeavySoul said:

Podie said:

I don't know enough about the ST170 lump to *know* but with those sypmtoms on a Duratec V6 I'd look at changing the IRMC.

Inlet Manifold Runner Control

On the Duratec V6’s it’s a “box” that controls a cable that opens the “secondaries” – known for expiring, and this lack of grunt above 3250rpm


I don't know how the VVT works on the ST170

[Evilbat]

HeavySoul I have an ST170 fuel rail and pressure regulator. Not too difficult to change. The most time consuming part is getting the injectors off ! Where in the UK are you ?

[HeavySoul]

Evilbat said:

HeavySoul I have an ST170 fuel rail and pressure regulator. Not too difficult to change. The most time consuming part is getting the injectors off ! Where in the UK are you ?

Bedfordshire chap.

PM me.

[GavinPearson]

I'd say it's likely to be a fuel flow problem, so change the filter and have the dealer run diagnostics.

The diagnostic procedures for that vehicle are extremely good, just have a dealer follow them and the vehicle will be repaired for the least amount of money.

[HeavySoul]

Well had the fuel pump replaced on Friday and have been driving hard all weekend and the problem seems to have been solved.

Thanks to everyone for all your suggestions and advice on this