mistuart

2014 Fiesta 1.6 tdci help needed

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Hi hope someone might be able to point me in the right direction with a problem I have on my 2014 Fiesta 1.6 tdci.

At idle if I try to raise the revs over 2000 rpm I get a hesitation and a big cloud of greyish smoke from the exhaust.

When driving I still get the hesitation at 2000 rpm the engine sounds noisy/ rattlily.

i get the engine management light on and the fault code P006A which points to MAF/ MAP sensor problems.

i replaced the EGR valve with a genuine Pierburg unit and checked all the vacuum pipe work checking for leaks.

i cleaned the MAF and MAP sensors, the MAP was coated in oil as was most of the inlet manifold/ piping.

i have noticed the turbo has a fair bit of play in the shaft and the oil is at minimum.

I am thinking the turbo could be dead and causing a big air leak but am open to any suggestions.

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5 hours ago, mistuart said:

P006A which points to MAF/ MAP sensor problems.

Try disconnecting the MAF. Usually the car will work without it, and if it is faulty, it can work better without it then with the bad one. It will cause a DTC, of course.

Next, I would either test or replace the MAP.

A bad MAF could do cause smoke. If the Turbo was under performing, it could cause smoke, but I would expect to see a Turbo DTC like P0299.

Since one is checked against the other, the DTCs can be misleading, faults in one can be mistaken for faults in the other.

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I have disconnected the MAF and it was still the same.

Had a look at a few similar problems and most people replace the MAF only to eventually find it’s another fault eg cracked air box to turbo pipe or leaky vacuum pipe which I have checked and are ok.

I have a fault code reader with live data, what values should I expect for the MAF and can I check it with a multimeter on resistance?

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17 hours ago, mistuart said:

P006A which points to MAF/ MAP sensor problems

P006A. Manifold absolute sensor - mass air flow correlation.

What that means is the flow measured by the MAF is compared to a calculated flow from the MAP, RPM & Intake air temperature. The EGR comes into this because it recycles engine gas, so the calculated flow includes the EGR flow, but the MAF flow does not. IE the Calc. Flow - the MAF flow should be the EGR flow.

The most likely air leak that will upset this is splits in the induction hoses from turbo via intercooler to the inlet manifold. Or leaks in the intercooler itself. I am not sure if you have checked that section. The splits are almost always hidden round the back of hoses in the most difficult to reach places though!

I have not looked at MAF flows in my car. I expect they are in units like g/s. As a 1st approximation, you can use the engine RPM divided by 120, times 1.6 litres, times the MAP reading in Bar Abs, times 1.2.

1.2 is the air density in g/litre at about 20C. At a different intake air temperature (IAT in deg C), multiply 1.2 by (293/(273 + IAT))

The MAP reading should be 1 Bar Abs if the turbo is not operating, or up to about 2.4 Bar Abs at full turbo. (1 Bar = 100kPa)

1.6 Litres is the engine swept volume.

120 converts RPM to full cycles (of 4 cylinders, or 2 revs) per second.

So 800rpm at IAT=20C and no turbo = 12.8g/s.

There will be a factor to account for valve opening times, tuning, and other engine related details, which could be 20% or so, but I have no real information on this, unfortunately.

That will basically be the calculation done by the ECU to get the flow to compare to the MAF. Sorry if it is a bit technical, but that is the way these things are!

Testing the MAF with a multimeter will not be very helpful unless you have a known good one to compare. And it may not be possible if it contains any electronic amplifiers etc.

Another thing to check on live monitoring is the IAT, as this is also used. That should be ambient with no turbo, but rise appreciably as the turbo cuts in (I get up to 50C quite often when climbing a hill at full power).

If you can log a live run over the full range of power, of RPM, MAP, MAF, IAT, EGR flow or opening, at least, it might be possible to see if there are unexpected deviations or inconsistencies in it. But it can be hard to pin down. That is why most garages and people proceed by changing parts, usually starting with the cheapest.

(For Technophiles only: The air density is approximate. Standard density is 1.225g/l at 1.01325 Bar abs (standard sea level pressure) and 15C or 288.15K. So at 1Bar abs and 20C it will be 1.189g/l. However the unknown engine specific correction factor make this irrelevant!)

 

 

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