Cruise Control bringing up Anti pollution warning

[Millerboy79]

Hello again guys,
My 2.2 hdi 2001 C5 is an interesting car! I have recently changed the maf and map sensors in order to cure a turbo charger solenoid valve problem, this seems to have worked to an extent but I am now left with 2 problems; the car now revs nicely to 2300, then holds back, clears and revs to 2700, holds back, then clears, revs to 3100, holds back and then struggles to get to 4000. When it clears it boosts nicely but the holding back feels like the boost being closed off. The map was new but the maf was 2nd hand and off an 807 2.2 hdi. The other problem is that the cruise now struggles to work, it sort of holds it at the set speed and then gradually the speed drops, increasing the speed with the stalk doesn't work so I have to use my foot (the bloody nerve!). Tried to use it this evening on way home from work and for the second time it threw up and AP at me and proceeded to lose power til it died completely (replete with chugging and smoke!). Usual thing, stopped it, started it, all was well and the AP went after 4 starts. Sorry for the long post but I was wondering if the cruise and the holding back were related? Is a brand new MAF in order?
Cheers guys
P.S. the MAF has never brought up a fault code, either with the old MAF or the new(2nd hand) one.

[cachaciero]

Doubt it's cruise related, in yourTurbo solenoid fault finding did you check that you had no vacuum leaks, much of the control system around the engine works on vacuum and leaks low vac will likely cause all sorts of strange behaviour.
Thinking about this further I wonder if you have a fuel pressure problem, if the rail pressure was low / failing then this could give you most of the symptoms you describe.

cachaciero

[Millerboy79]

I've replaced the turbo solenoid valve and checked all the vacuum pipes which were all intact and holding pressure well. It's never brought up any faults relating to the fuelling when I've coded it, however as we all know with a Citroen it doesn't necessarily have to bring up a fault relating to the problem! lol

[Millerboy79]

On a further point with this thread, it has started to fall over more regularly now, usually while maintaining a constant speed and the fuel economy is c**p. Went to Birmingham the other day and while cruising on the motorway it fell over and only managed to achieve 30 mpg average consumption at best. Oh and the holding back is starting lower down in the rev range now too, and its sluggish as hell when cold and won't rev happily until its been flicked past 2000 rpm. In general it seems down on power between 1000-2000 which makes pulling away awkward at times.

[cachaciero]

Have you checked that the swirl valves are operating correctly?, they should be closed, arm fully forward between 500 -2200 rpm after which the valves should be open arm fully aft. Valves open at low revs can / will cause poor performance and higher fuel consumption, don't know about effects on cruise control though.

EDIT Note
Cruise speed on motorway i.e 70 on the auto box version gives revs very close to the swirl valve operating point, i.e for much of the U.K motorway speed range the valves will be closed (operating as a 12 Valve engine).

cachaciero

[Millerboy79]

I presume you are referring to the swirl chamber in the inlet manifold? I've replaced the actuator with a new unit from Citroen and checked the vacuum by bridging the pipes, the vacuum is good but I have yet to see it move while the engine is revving (obviously I can only test it while stationary and not under load.). It holds the swirl valves fully closed at all times, or so it appears. I only mentioned the cruise because it seems to have the issue more while maintaining a constant speed.
I shall try a different solenoid valve on the swirl valve and see what happens, failing that my gut instinct keeps coming back to the MAF being incorrect/on its last legs.

[Millerboy79]

Also are the swirls linked only to engine revs or do the readings from the MAF affect their operation as well?

[cachaciero]

The book of words I have only refers to revs and reving the engine to 2.5 K car stationary is enough to make them snap open. Swirl valves is a bit of a fancy name for what is in effect a shut off valve for the second inlet valve. It is not clear what the exact reasoning is behind the operation of these valves as I can see little high end difference between then being open or shut, having driven for a while with them wired shut, there is a lot of low end difference if they are open at low revs. I suspect that part of their existence is to improve exhaust gas induction at higher revs for the EGR function but that is speculation.

cachaciero

[Millerboy79]

Hmm, I'll try a different solenoid valve on the swirl actuator and see if anything happens. I have noticed when it drops into limp home mode I can't hear the turbo spinning!

[Millerboy79]

Right, I revved the engine well past 2500 rpm and the swirl arm didn't move. I have checked the vacuum to the swirl solenoid and from the swirl solenoid and there is a good strong vacuum there. I then tried another solenoid (that I know to be working) and still no movement from the swirl arm. Now confused. Still got no power at low revs, still got hesitation and still got poor fuel economy. Still a crap car basically.