Advice please !! Seat Alhambra rough running & reduced power above idle -

[markdaniels]

I have a 2001 115bhp Alhambra (1.9 TDi PD AUY engine), which has now covered 204K. Over the course of the last 2 months on my 250 mile round trip daily commute, I have noticed a definite loss of power and more recently the car is running rough as if misfiring (possibly on more than 1 cylinder) when revved above idle or driven. Car still pulls away OK, though it struggles with full tilt taffic light starts, but that may also be an age thing!
The symptoms were evident before having a new cam belt & tensioners fitted last week.
Other than the lack of power and rough idle, there are no other outwardly noticable symptoms - No smoke on start up / idle, some under load (but not lots), but still regularly get 55+mpg
Following a visit to the forums for pointers, I have cleaned the EGR and pulled a fault code (17569 - Manifold Temp Sensor).
Now my short list of causes is
1 in-head injector loom
2 manifold temp sensor
3 coolant temp sensor
Any help / advice as to what to change and in which order would be much appreciated.

[markdaniels]

Update to information above:
I have logged in the OBD and having cleared all fault codes, cannot replicate the manifold temp sensor fault that was first registered in the system. Does this mean that bit of kit is no longer part of the issue if it's not returning a fult status? Also, having enquired about costs for this sensor with Seat, i have had mixed responses from my local parts departments, with one quoting me £40, and the other saying they cannot locate such a sesor on their schematic / exploded diagrams! Anyone got a definitive answer to does it exist and where does it reside on the engine?
Whilst on the OBD viewing, i disconnected the injector loom, and got it to throw a fault code, which was resolved / removed once re-connected. With all that's going on, still getting no fault codes being thrown up as a regular occurance.
Also, noticed quite a lot of oily deposits around the freshly cleaned EGR (below the vacuum connection on the top), is this usual or has something given up inside the EGR?

[zollaf]

throw a new injector harness at it.

[markdaniels]

Further update : have checked out my original injector wiring loom and can find nothing wrong in terms of cable failure / continuity.
I have installed a new loom this morning but still have same symptoms, with no change whatsoever.
I have a copy of Elsawin and have found reference to the manifold temperature sensor being electrically connected at the same connection point as the manifiold pressure sensor.
Can anyone tell me if this is a dual sensor that does both temp & pressure and if so, can it throw a fault code against either aspect of its sensing parameters?
Have also looked again at the EGR and again its well coated with oil, is this normal or does this indicate an EGR failure?

[markdaniels]

Update to info :
On the way into work this evening i have been taking various logs via VCDS, and now i'm starting to digest some of the info i can see that even at at steady cruise of 50 miles or so at 80mph the coolant temp never got above 78 degrees but the dash indicator suggests temp steady at around 88 / 89 degrees.
Will be changing the temp sensor and thermostat in the morning to remove any possibilty that these low numbers are contributing to the problems.

[markdaniels]

Further update :
Have now replaced temp sensor & thermostat, and now have correct operating temps for coolant, but if anything, these changes have now made the idle lumpy where it wasn't before!
MPG on steady run into work now dropped to mid 40's, which though while is still a good number, is nothing like what i've been getting from similar trips recently.
Have noted from other posts that a clogged fuel filter could add to my problems, so now going to replace fuel filter tomorrow as i can't remember the last time this got changed at service - maybe 3 - 4 years ago!
Now also considering the timing / torsion settings as i have recently installed a new cam belt & tensioners etc - my values are generally very similar with a variance between -0.6 & 0.0 and this has remained constant over the last 3 days of measurement recording.
Does the torsion need tweaking after a new cam belt? if so, this could well be the issue, but i'm conscious that the rough running was evident before the belt change.

[markdaniels]

Update :
Just finished changing the fuel filter and have retarded the timing from 0.0 to -1.7.
No change in the misfire, although the lumpiness has been eased and the engine does seem to pull more freely again from low down.
Have now booked the car in next week for a thorough diagnostic session with local diesel specialist.
Will keep you informed of progress.

[zollaf]

sorry the loom didn't cure it, it usually does. i'm all out of ideas for you apart from trying some quality injector cleaner such as forte.

[markdaniels]

Have been using Millers for the last 30K or so, so i don't think the problem lies with poor spray patterns.
I suspect as no codes and all electrics checking out ok, that it may be a mechanical issue with one of the injectors, but i don't have any form of test equipment for diagnosing issues with injectors hence it's booked in with the diesel specialist.

[markdaniels]

Update :
Retarded timing may have helped the lumpy idle a bit but it destroyed my MPG. Have now advanced the timing to 1.0 to 1.7 and am back to proper hypermiling numbers once more, but am finding it easier to get the car in the sweet spot for high MPG, and keep it there!