Can anyone help interpreting an ODBII log created during intermittent power loss?

[champers]

Ford Focus Hatchback 2.0 TDCi Zetec 5d 2007 49,000 miles

I have a problem every 4-6 weeks when the engine revs die suddenly and the only solution is to release the accelerator pedal and gently re-apply. The same thing then happens again and this can carry on for about 20 minutes and but then clears for another few weeks. By driving very gingerly, I can usually stay on the motorway (I don't use the car much but mostly for long distance trips) but have occasionally had to pull over onto the hard shoulder to avoid being shunted from behind etc., where after 20 mins of idling I am Ok to set off again.

This situation has been going on for years and I hoped that an engine warning light/diagnostic code would one day be generated - but nothing! Hence, apart from checking hoses, upgrading the ECU and replacing fuel + air filters during regular servicing the various Ford Delears can not help me unless I want to invest in swapping over more components. 

I did buy an ODBII logger and capture 4 sequential power loss events whilst out on a country road - however, the only values available to me are Engine RPM, Fuel Rail Pressure, Engine Load, Intake Manifold Pressure, Mass Air Flow rate and Turbo Boost&Vacuum and when shown to the garage, I get the "it could be anything" response.

I have attached a PDF if some kind soul wants to take a look. One clue is that it only ever happens when the engine reaches operating temperature

Many thanks

Car data.pdf

[gmonag]

That fact that the MAP falls to zero and flat lines at each event suggests that the sensor or wiring may be at fault. Resist the temptation to swap parts on spec - it gets expensive and may get you nowhere. Test the sensor and wiring with a multimeter.

Greg

[Tdci-Peter]

9 hours ago, champers said:

I did buy an ODBII logger and capture 4 sequential power loss events whilst out on a country road - however, the only values available to me are Engine RPM, Fuel Rail Pressure, Engine Load, Intake Manifold Pressure, Mass Air Flow rate and Turbo Boost&Vacuum

Forscan would be able to show more PIDs, it is only £15 for a usb adapter & free download.

Both the MAF & the MAP readings are suddenly dropping. It is hard to see which drops first.

The Boost pressure is just the MAP reading offset by 1 bar. There is no separate sensor.

If the MAP was faulty, then why does the MAF drop? And vice versa. Also MAF & MAP are compared inside the pcm because MAP & RPM can be used to compute air flow. An error here usually gives a DTC. 

I think this engine has a throttle valve, sometimes called an anti-shudder valve. If that was closing briefly, it would interupt the air flow & look like that.

The fuel rail pressure will surge when the injectors suddenly shut down, caused by the  real or apparent drop in air flow.

[Quint]

I'm surprised it doesn't have an error code. If this is the case, then probably there is a vacuum leak from the intake side? Since its made of plastic and rubber, perhaps looking for cracks from the air cleaner>MAP>intake tube>intake manifold would be a good exercise. A "smoke test" or carb cleaner test (for petrol) was done on our older cars to check if this was the case.

[gmonag]

Any update on this problem?

[champers]

Thanks to everybody who replied.

TDCI-Peter - thanks for the tip about Forscan. I haven't bought the windows version just the app which I now have on an android phone and am logging every trip in anticipation of it happening again (as mentioned every 4-6 weeks with my usage)

Why oh why there is never any error I do not know but have checked this by a variety of methods (torque pro/forscan, holding stalk in when turning ignition, requesting garages to check). I hadn't thought about the anti-shudder valve - interesting   

Quint: I checked the hoses and wiring/connectors as best I can with on-street parking and the ford dealerships have in the past but will aim to get to a workshop for another look

Gmonag: I haven't checked the MAP sensor with multimeter, it is apparently logging the correct values 99.99% of the time, it's just on motorways it flatlines

Another thing I will try, next time it happens, is to pull over and let the car roll to a stop with my foot flat down on the accelerator pedal and see whether this unnatural situation (engine on, in gear, accelerator down, no revs, no forward speed) triggers a DTC

PS. I asked for the ECU firmware to be updated a few years ago and the sticker on the cabling underneath says "6M5T - 14014" - that sounds OK doesn't it?

 

 

On 10/15/2016 at 2:53 AM, Tdci-Peter said:

Forscan would be able to show more PIDs, it is only £15 for a usb adapter & free download.

Both the MAF & the MAP readings are suddenly dropping. It is hard to see which drops first.

The Boost pressure is just the MAP reading offset by 1 bar. There is no separate sensor.

If the MAP was faulty, then why does the MAF drop? And vice versa. Also MAF & MAP are compared inside the pcm because MAP & RPM can be used to compute air flow. An error here usually gives a DTC. 

I think this engine has a throttle valve, sometimes called an anti-shudder valve. If that was closing briefly, it would interupt the air flow & look like that.

The fuel rail pressure will surge when the injectors suddenly shut down, caused by the  real or apparent drop in air flow.