Ford Focus - Ford TDCI limp mode issues

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Wed 7 Jul 2021 14:33
Ford Focus - Ford TDCI limp mode issues - _Dan_

Hello all.

Firstly sorry for the long read - I want to give as much info/diagnostics as I can to try and get to the bottom of this...Really hoping someone can give me some advice on this as its driving me mad here!

So I have a 2008(58) Mazda 3 1.6d - using the Citroen HDi/Ford TDCI engine all mechanics seem to know and hate. Its Euro 4 so it has the EGR but no DPF.

About a month ago it went into limp mode. It still drove but really struggled to get above 3k RPM and was very sluggish to pick up speed when driving. The weird thing was when the car is first started it drive perfectly for about the first 15 -.20 seconds then straight to limp. Turn her off and straight back on and its the same every time. Seems like the turbo isn't boosting.

That lasted for a few weeks and then it cut out while driving. AA recovered to a garage who confirmed AA diagnosis of EGR valve and replaced. £350 later I picked the car up. Mechanic advised the car also had a problem with the boost solenoid and so was still down on power but would drive. (I know the EGR was at least partly at fault as it had been diagnosed by a different mechanic previously).

I managed to pick up a boost solenoid online and fitted that myself. Confirmed vacuum right up to the turbo (took pipe off the turbo actuator and can feel it sucking) but its still exactly the same. Drives perfectly when first switched on but then goes into limp mode.

Now I know the vacuum is good right up to the turbo. I know the turbo and actuator are working as the car drives fine on startup. I have a cheap code reader which finds no faults at all on the car and there is no EML (the code reader does work - I unplugged the MAF to generate a code which was picked up no problem).

At this point I don't know where to go next as I have no diagnostic info to work on and everything I can think to test seems to be working fine.

I'm leaning towards it being a mechanical issue rather than anything electrical as no codes or EML. Makes me think its something the ECU thinks is working but actually isn't. Maybe a sensor generating false readings?

I loathed to take to any more garages for diagnostics as I'm already nearly £400 into this and the car probably isn't worth much more than that anyway.

Hoping someone here might be a bit more familiar with these engines and have some idea on what I could check next?

Thanks for reading this far!

Dan

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Thu 8 Jul 2021 12:48
Ford Focus - Ford TDCI limp mode issues - Gibbo_Wirral

Quite often cheapo (and even expensive) scan-any-car code readers will fail to fully talk to a car's ECU and get all the codes.

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Thu 8 Jul 2021 13:52
Ford Focus - Ford TDCI limp mode issues - _Dan_

Thanks for the reply.

I thought this too, but the lack of any EML lights at all + the lack of codes on the reader (I actually tried 2 separate readers) make me think there might be something else going on.

I've unplugged the MAF to test and it threw a pending code straight away and the EML after about 10 mins of driving so I know that side of it works. Everyone I've spoken to has said they don't know why the light hasn't come on - I can only think its something mechanical that ECU thinks is working?

Or maybe a faulty sensor somewhere that is reporting default values or something so the ECU thinks its all good?

I'm out of ideas here really.

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Thu 8 Jul 2021 14:17
Ford Focus - Ford TDCI limp mode issues - elekie&a/c doctor
Are you sure the turbo is ok? I would check the integrity of the impeller and shaft to make sure it’s spinning correctly.
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Thu 8 Jul 2021 15:56
Ford Focus - Ford TDCI limp mode issues - _Dan_

It seems to be fine as the car drives absolutely perfectly for the first 10-20 seconds after starting. I can pull up on a quiet straight piece of road, flick the key off and back on and accelerate with full boost and no issues at all. It'll then drop into limp mode until the next time I start it up. I assume if the turbo was bad it wouldn't work at all?

I've also taken the inlet pipe off and the turbine spins free with no play in it. I can also feel the pressure building in the rubber pipes when its revved so I'm pretty sure its all working as it should.

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Thu 8 Jul 2021 21:55
Ford Focus - Ford TDCI limp mode issues - focussed

The "solenoid" you fitted seems to be a vacuum diaphragm boost control.

You need a turbo pressure gauge to adjust it so it does not overboost the engine, or there may be a static mechanical setting measurement for the travel of the control rod, in which case you will need a manual vacuum pump to operate the vacuum device while doing the setting.

The MAP sensor senses the manifold pressure from the turbo, if it exceeds the value set in the ECU it will put the engine into limp mode to protect the engine, exactly as you say is happening.

Try an owners's club technical forum for a DIY how to do it.

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Thu 8 Jul 2021 22:55
Ford Focus - Ford TDCI limp mode issues - _Dan_

Thanks for your reply. Sounds like a promising lead to follow up on.

In terms of "setting up" the new solenoid (it was one of these), I wasn't aware that might be a thing. I assumed that as the symptoms haven't changes since before to after the change it likely wasn't actually at fault.

The MAF sensor looks like it could be a good place to start. I just posted a thread over on the Ford Owners club so hopefully someone there will have some advice.

Thanks again for taking the time to help.

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Thu 8 Jul 2021 23:35
Ford Focus - Ford TDCI limp mode issues - elekie&a/c doctor
A cheap code reader is unlikely to give adequate real time data . Perhaps someone with a better scanner could help . Interpretation of this data is the key to a fix . Has the fuel filter been renewed ? These engines are very sensitive to any loss of fuel supply.
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