Houston, I have an EGR fault !
I'm smiling about it because it is very good news. First of all it proves that the monitoring system is working, the ECU knows something is wrong. It didn't actually give me a warning but when I connected up with the laptop I found the first error I've had since drilling through the dpf, and, the error with the EGR is a sign that the dpf drilling has reduced the exhaust backpressure significantly (not that I needed to be told again !)
The error code, ( I didn't write it down, P0401 I think) indicates low EGR flow.
When I got the car it had an EGR valve exit orifice plate fitted already, which I didn't already know. It's the official Alfa solution to reducing the flow of EGR gasses. I bought a second plate, an EGR inlet orifice plate, with a 6mm hole in it and fitted that too - which gave me fault codes for low EGR flow, so I drilled it up in stages to about 9mm, allowing a little bit more more EGR flow each time, until I stopped getting the fault codes. Then I knew the EGR was passing only just enough exhaust gas into the inlet to keep the ECU happy, and no more.
Now that my dpf has been opened up the excessive exhaust backpressure has gone and the EGR flow rate will also have subsequently dropped off. Today I'll either drill out the EGR inlet orifice plate some more or just remove it completely.
In the link contained in the message above, about the BMW with a blocked dpf, it's interesting to think how easily an EGR valve and a DPF can cause a downward spiraling of performance if either of them aren't operating as best they can. A leaky EGR increases soot levels slightly but mainly lowers the exhaust gas temperature, EGT. The lower EGT prevents much passive regeneration from taking place in the DPF and soot loading increases. Rising soot loading in the DPF means the exhaust backpressure increases....and increases... and more sooty exhaust gas flows through the EGR...and the temperature comes down a bit more....
Anyway. I changed my oil less than 10k miles ago. Since having such a badly blocked DPF which caused the high backpressure it means that soot will have been blowing past the piston rings and into the oil. And on the regens, more than normal amounts of diesel will have also been blown past the rings too. I've noticed the top end starting to sound a bit noisy this past month or so and thought I should check my oil anyway.
So I've dipped my oil today and it's now the blackest, smelliest, good quality engine lubricant money can buy. Where I wiped some onto the back of my hand and then wiped it off, my skin is stained from the soot, almost as if I had wiped my hand on the back of the BBQ. So no doubt too, the filter is likely to be gubbed aswell.
Now, bearing in mind that mine has become this contaminated *with two EGR blocking plates fitted* , what would it have been like if I didn't have either plate ?
So I guess this is the start of wondering about long term strategies. I'm not going down the remap route myself not least of all because my clutch is the original clutch with over 133,000 miles on it now, and in January this year when it was very cold I think a lazy adjuster or something else was causing it to slip, only marginally, when pushed hard. Since the weather warmed up it has been fine. i've read some similar comments from other owners too.
So in the interests of clutch preservation, among other things, for the time being there will be no remaping for me.
Obviously, the EGR and DPF, although not interdependent components by function, they are able to feedback some of the negative effects of one another when either of them doesn't work to full efficiency. The DPF causes more backpressure when it's blocked, increasing the flow of exhaust through the EGR, which gums up swirl valves and lines the inlet too.
I don't think it matters which job is dealt with first to be honest, A blocked DPF is always easy to relieve with a drill, or if yoiu want to use cleaners, like in the posting about the sick BMW, the intake cleaner also acts as a DPF cleaner. The Wynns intake cleaner sessions talked about on these forums might be something to think about, if you want to leave the cleanup to someone else.
The EGR blocking plate has got to be a must have accessory. You fit it once and forget about it.
Cleaning the intake either in situ, like I have previously done, or by removing it and cleaning it in the garage, will give access to the swirl valves to allow you to confirm they're operating properly (With FES and ALfaOBD you can operate the swirl valves through software too, so yoiu can hear when they don't move because there is no noise. A crude but quick test)
And the DPF should really be kept in good health if yiou aren't going to drill it out, replace it with a new DPF or a bypass pipe. That means taking the trouble to make sure you get the dpf up over 350C now and then. Some sustained motorway or dual carriageway driving will help with that. Better than that, if you pull off at a junction and immediately rejoin the motorway at the same junction from a slow speed, and then accelerate as hard as possible through the gears, by the time you have rejoined the motorway and are up to legal speeds the dpf will be getting up to well over 400 celsius (according to the many tests which I did)
Well, it was payday yesterday, so I'm going to go and spend some of it on engine flush, fresh oil and a new filter. And then I'll remove the EGR inlet orifice plate, and perhaps also look for a 2 inch core drill, and if I find one cheaply enough I'll run it through the dpf core. After this, fingers crossed, my car expenses will be falling off because I'm never buying another additive (though I do use 2-stroke oil in a tankfull now and then still, and might use an injector cleaner every 20k), and because of the rise in mpg as a result of drilling the DPF.