Engine running problems - case closed

[Roberltd2]

Hi everyone,
I’ve been experiencing a few issues lately with the Zed so I’m hoping somebody out there might be able to give me a few pointers.
It started last Friday as I left work. I started the engine and it briefly seemed to rev much higher than I would have expected before the engine settled down to normal idle.
As I pulled into the BP garage just before arriving home, the revs increased of their own accord for a few seconds so now I was certain I hadn’t imagined things previously.
As it was chucking it down (and dark) by the time I got home, I decided to look into it the following day.
It was another wet & windy day Saturday so I thought I’d see how the car behaved on the weekly shopping trip. It ran fine on the outward run but as I descended downhill on the final mile or so towards home, the engine started sounding very rough and I could hear some muffled popping coming from the exhaust on the over run.
I made it back thankfully and straight away got the Creator 310 out to check for any fault codes. What it gave me was:

2C7F DME Lambda Control 2
2A38 DME Valvetronic, Monitoring, Sluggish Movement,

I’d read somewhere (the Forum I think) that the 2C7F code could indicate air ingress in the system so this morning I did a visual check for any split / perished vacuum hoses which might be causing a lean mixture but couldn’t see anything obvious.
Is there a way I can use the Creator 310 to tell if the (downstream?) lambda sensor is working properly?
I started the engine up but everything sounded ok apart from one instance when the revs suddenly increased then decreased over a period of four or five seconds just as they had in the filling station previously.
I also removed the plastic engine cover and noticed that oil was smearing down from the eccentric shaft sensor connector. When I removed the connector I could see straight away that it was quite oily and that some oil was inside where the pins are. This was disappointing to see as I’d only had a new sensor fitted in March of this year and they are not cheap. I’m hoping a new seal will rectify this problem, but I’m also wondering if it would be related to the idling issues and the fault codes or is that a separate issue?
I’ll try to get the car over to my mechanic as soon as I can but thought I would share my predicament in the hope that it might help to get it sorted out.
Thanks and a Happy New Year to everyone!
Robert.

[enuff_zed]

I suspect the lambda code has been caused by the rough running.
When the sensor was replaced did a new seal get fitted? It is the leaking seal that allows oil into the sensor.
Before you look at anything else I’m afraid you will have to fit another new sensor.
Fairly easy to do yourself and I don’t think the ones I’ve fitted have been too pricey.

[Roberltd2]

There was definitely a new e.s.s. seal fitted as I'd had a new (Febi) cylinder head cover fitted as well. This came with a sensor seal fitted pre installed but my mechanic swapped it for the seal I'd bought from Autodoc because he thought it was a better fit!. I had the impression that the oil near the pins had seeped in from the outside rather than having come up throgh the pins. I hope it's ok because the Vemo one I bought was a couple of hundred plus. Which ones have you used? I thinking fitting would be above my pay grade as I think the cylinder head cover has to be removed for fitting? Thanks for the reply.

[enuff_zed]

Yes the oil comes up between the seal and the body of the sensor then drops down onto the pins.
You could try some contact cleaner on the pins but it will be a temporary fix.
I’ll dig out the sensor I bought.
This is a 4-pot I assume?

[enuff_zed]

Can’t find it on my past eBay purchases right now but I know I simply pasted the part number in and got one for about £35.
Have to say it is disappointing your mechanic chose not to use the one that was already fitted.

[Roberltd2]

It's a 6 pot 2.5si, 2007 facelift E85.
Yes it's a shame about the seal.

[enuff_zed]

It's a 6 pot 2.5si, 2007 facelift E85.
Yes it's a shame about the seal.

Ah ok, my experience was with a couple of N46s but I believe the principle is the same.

[javis20]

I've had this problem and it related to the oil coming up thru the pins, not the seal. Defective sensor. I replaced with VDO and it's holding up well. Not sure where your located, but here in the states garages have a 1 year warranty on workmanship. You might be able to get the garage to redo the job. Otherwise, it's really not a difficult job to do.

[Roberltd2]

I'm hopining for something along those lines as well. The one I bought was Vemo. Thanks.

[Roberltd2]

Things definitely improved in the days following my original post but I decided to pay a visit to my mechanic anyway.
Needless to say, when I arrived at the garage the engine was running like a watch. The mechanic thought the amount of rain we’d been having over the previous couple of weeks might have been the cause of my problems, so he suggested trying a fuel system cleaner first and to bring the car back if the symptoms persisted.
Got some fuel system treatment from Halfords. Pre treatment the display was showing 36.2 mpg.
Within about a week and about half a tank of fuel this figure had gone up to 37.6 mpg. Not as dramatic as I’d hoped for but at least better.
I also fitted a new eccentric shaft sensor seal which is a much better fit than the old one. The material seems to be more pliable and the internal diameter is 21mm compared to 24mm of the one which it replaced after nearly ten months of use. Would that length of time be enough to harden the rubber and round out the internal diameter I wonder?
I’m hoping that I’ve avoided the need to replace the eccentric shaft sensor.
I also gave the mass airflow sensor a clean although it looked pretty clean to me as it was.

Not related to the engine issues, I’ve also replaced the Bosch wipers with a pair of Halfords branded Flat “aero” Wiper blades (18” and 20”) because of the amount of juddering which was happening with the Bosch items.
I was a bit sceptical when I bought them but thought they couldn’t be any worse than what I had. In fact so far they’ve been brilliant. Super smooth and quiet and they clean the screen really well too.
So thanks again for all the advice and also to Halfords for the windscreen wipers and the Wynn’s Formula Gold petrol fuel system cleaner.