Didn't have a huge amount of energy available today as I'm still feeling like death from the booster jab on Friday, nevertheless I was determined to get a few things done.
First up was getting the interior of the S123 back into a presentable state. Calling it clean would be overselling it, but it's a heck of a lot better and I'm not embarrassed by it any more. Sadly attempts to find a working jetwash to do something about the outside were fruitless. Nevertheless, the interior is better at least.
It's no longer approximately 87% dog hair by volume at least.
Should be off to a new owner in the next couple of days.
Moving onto the Caddy it was time to have a look at the EGR valve to get an idea of how funked up the system was.
My the standards of most modern cars it's thankfully pretty easy to get to. The arrow is pointing at the vacuum actuator rather than the valve itself, but you get the idea.
Given the position of the securing collar I don't reckon it's ever been off. However the innards weren't anywhere near as bad as I was expecting.
Yes it's pretty grim, but I'm not unused to seeing these things totally choked solid on far newer vehicles.
Probably about 0.5mm worth of caked on gunk the whole way round.
The other side of the valve is more disgusting as it's sticky, tarry crap as the PCV system feeds into the EGR circuit right next to the valve. I did dig an appreciable amount of gunge out of the valve body, but it definitely wasn't totally choked nor did it seem to be sticky.
I'd also been able to confirm that the valve is sealing completely and consistently when closed.
Reassembled everything...and absolutely no difference. Very slightly surging engine speed still there (it does exactly the same at any engine speed I found, regularly once a second), along with excessive smoke on light throttle.
Definitely have vacuum at the EGR valve, and you can hear it physically snap shut if you pull the vacuum line off. It however doesn't really have any noticeable effect on the running of the engine either way.
One thing I did notice is that when this behaviour is present, the rev counter also behaves slightly erratically, randomly twitching upwards from the actual engine speed - and it seems to do it more when on the throttle than off.
Then out of nowhere, the engine completely smooths out. The note deepens (because the flap on the intake, which I assume works in partnership with the EGR valve is now fully open), and the diesel clatter becomes a little sharper, so something has obviously changed - I'm guessing with the injection timing. Checking the EGR at that point shows there's no vacuum present, so the ECU isn't calling for the EGR system to be in operation. It's also noteworthy that after this point when things decide to behave that the rev counter twitching also stops I'm increasingly convinced these two symptoms are connected in some way.
So I don't think the EGR valve is the cause of this issue...bit it's definitely *involved* in it. Think the next step really will be to find someone locally with VCDS and get a look at some real-time data. Everything being fly-by-wire here makes guessing pretty pointless... imagine on a newer car we'd have a check engine light illuminated - but this car doesn't have one!
The rev counter misbehaving being clearly tied into it is making me think camshaft/crankshaft position sensors? Or however else the ECU gets the engine speed/position data...makes sense though if there's a disparity between the requested and reported engine speed, it would throw the fuelling all to hell.
Think it's likely been like this for a while so I'm not worried about it really, but I'll be damned if I'm not going to try to get to the bottom of it. Especially as the van drives so much nicer when this fault is staying out of the way.
We got any SDi experts on here?
Oh...and I've ordered a replacement engine cover. Looks quick and easy to fit/remove unlike many, so I'm not adverse to its being there.
Something which may well be getting changed in the not too distant future - which is a shame as they're only a year old - is the tyres. I had to brake moderately hard to avoid a suicidal pigeon this afternoon and discovered that these tyres really aren't great on a cold, damp road. Also the front ones have way more grip than the rears...great, aside from when all four wheels lock up, then the front regains grip well before the rear - which by then has started to try to overtake the front. It was a moderately firm braking manoeuvre, but I didn't expect quite *that* degree of upset. Even the big van would have been okay.
Methinks some Uniroyal rubber may be in the future. I will get the tracking checked in the meantime though - not least because the steering wheel is slightly off straight and means I can't see about 2/3rds of the warning lights on the dash when driving straight ahead. Bit of a daft design there from VW. Likewise the switchgear most of which is hidden behind the steering wheel.