C8 2.2HDi really hates hills - turbo or DPF issue perhaps?

[aspire_helen]

The swirl valve (actually 4 butterfly valves on the same shaft) defaults to closed, at engine off and idle. The fact that it is "spring-loaded" closed does not mean that it is opening when it is supposed to. It opens at higher engine speeds and fuel flow rate. eg above 2100rpm at (coolant?) temp 80degsC , and above 2500rpm at temp 0degsC. The minimum fuel flow rate has to be 40mg/engine stroke. I suspect (but do not know) that the swirl valve function is recorded on Lexia, and perhaps as a "actuator test".
At the end of the day, the variable swirl system is primarily intended as a pollution reduction process rather than power. With the valve(s) closed, the inlet air is channelled via "short" ducts cast into the inlet manifold. When the swirl valve(s) open, additional "long" ducts opens up. When the air exiting the short ducts re-mixes with the air exiting the long ducts, more turbulence (swirl) is produced which provides for a more efficient air/fuel mix in the combustion chamber.

[MattBLancs]

At the end of the day, the variable swirl system is primarily intended as a pollution reduction process rather than power. With the valve(s) closed, the inlet air is channelled via "short" ducts cast into the inlet manifold. When the swirl valve(s) open, additional "long" ducts opens up. When the air exiting the short ducts re-mixes with the air exiting the long ducts, more turbulence (swirl) is produced which provides for a more efficient air/fuel mix in the combustion chamber.

That's not quite my understanding, my understanding is, low revs = butterflies shut = only one inlet valve per cylinder is active. Hence higher velocity in the inlet tract/duct, so more swirl, better mixing, less soot, etc, etc.
Higher revs, get as much air into the cylinders as possible, loads of flow means high velocities and lots of swirl regardless= open butterflies and 8 inlets valves functional. (Obviously the inlet valves all still open and close whenever the engine is running, just 4 of them are doing so for no benefit when the butterflies are shut, isolating that route.

I'll try to find a reference for my understanding of how the swirl "system" works if I can.

[Rp0thejester]

That's the problem with the C8, access to the engine, mine has had a recon engine fitted in the past. There used to be a company out there offering engine swaps as it would work out cheaper on labour costs in the long run as a stuck injector could cause alot of labour costs.

[aspire_helen]

Having re-read Citroen's training manual, I believe i have fallen into my own trap. In the following post -
"Definitive Guide on DPF/Additive/EGR/Injection etc for early C5, Peugeot406 with DW12 HDi engines" - I referenced Citroen's Technical Training Document REF N°: 1.6.243 August 2000, which covers the 2.2HDi DW12 engine and BoschEDC15C2 Injection Control Unit. For clarity, and correction, I reproduce an extract below. Some such definitive documents are available to download from the internet, and, if available on this forum, would provide definitive information.


VI - VARIABLE "SWIRL"
a - Short inlet duct (helical shape)
b - Long inlet duct (tangential)
Using the short inlet duct allows maximum swirl to be obtained (swirl movement).
Air is let into the inlet ducts by opening the "Swirl" control butterfly valve at high engine
speeds. Using 2 inlet ducts allows maximum filling (reduced swirl).
Advantages of the variable "Swirl":
· optimisation of combustion (air/fuel mixture),
· better performance/pollutant emissions compromise.
The variable "Swirl" gives a reduction in carbon particles

Warning: The "Swirl" control throttle is closed when it is not controlled
pneumatically.
Conditions allowing the throttle to open:
· engine speed above 2100 rpm (at 80°C) (2500 rpm at 0°C),
· injected fuel flow greater than 40 mg/stroke

[MattBLancs]

Having re-read Citroen's training manual, I believe i have fallen into my own trap. In the following post -
"Definitive Guide on DPF/Additive/EGR/Injection etc for early C5, Peugeot406 with DW12 HDi engines" - I referenced Citroen's Technical Training Document REF N°: 1.6.243 August 2000, which covers the 2.2HDi DW12 engine and BoschEDC15C2 Injection Control Unit. For clarity, and correction, I reproduce an extract below. Some such definitive documents are available to download from the internet, and, if available on this forum, would provide definitive information.


VI - VARIABLE "SWIRL"
a - Short inlet duct (helical shape)
b - Long inlet duct (tangential)
Using the short inlet duct allows maximum swirl to be obtained (swirl movement).
Air is let into the inlet ducts by opening the "Swirl" control butterfly valve at high engine
speeds. Using 2 inlet ducts allows maximum filling (reduced swirl).
Advantages of the variable "Swirl":
· optimisation of combustion (air/fuel mixture),
· better performance/pollutant emissions compromise.
The variable "Swirl" gives a reduction in carbon particles

Warning: The "Swirl" control throttle is closed when it is not controlled
pneumatically.
Conditions allowing the throttle to open:
· engine speed above 2100 rpm (at 80°C) (2500 rpm at 0°C),
· injected fuel flow greater than 40 mg/stroke

Good information, I'll seek out the document(s) you've mentioned, sounds a good resource

[tearing hair out]

Thank you for the all the detailed information, @aspire_helen especially!

Almost certainly incorrectly, I changed the DFP anyway - it wasn't THAT expensive. The garage didn't reset the DFP state and fluid level (they'd already topped up the fluid, though not to full), but I've just done that. I'll drive it for a few days and see if it's made a difference. The two P1442 additive level faults are now cleared, though I still have the cap sensor and pre-post heater ones to address, potentially.

I suspect it does enough motorway driving - 20 minutes each way most Sundays (and that's about 30% of the total use of the car) - so the pre-post heater circuit probably isn't being used in regen anyway.

I do have Lexia, so I can check of the injector parameters in the next few days, and make a video. From memory, there's a delta of about 2 units on injector 3, but I have no idea what the tolerance should be, so I don't know if that's indicative of an issue.

I'm finding that, the longer I drive it, the more used to the lack of power I get - so eventually it'll be "fixed" by rewiring my performance expectations, I guess!

Oh, and I found a few posts suggesting they were having performance issues related to a poorly adjusted throttle cable. I've tightened mine - and Lexia shows 97% at full pedal travel. It's not made a difference, so I don't think that's my problem either.

[aspire_helen]

Your very first post highlighted Lexia's Pre-post Heating Fault P0380 "Short circuit to positive". I had exactly the same. The fault description proved quite accurate...the sole connector between the glow plugs and the controller/relay had overheated causing a high resistance (900 to 1500 ohms). The diagnostics would be looking for a resistance of all 4 glow plugs, ie a few ohms, so my 900 to 1500ohms would have been diagnosed as a short circuit (of the positive power lead to the plugs). Having fixed the plug, the fault cleared.

2001 C5 2.2HDi -P0380–Over-heated glow plug connector
Post by aspire_helen » 12 Jul 2023, 22:49

[Paul-R]

Not doubting that lead was at fault but surely a high resistance would be read as an open circuit?

[tearing hair out]

I'd expect that a short across one of the glowplugs would give "Short circuit to ground" - or possibly nothing since the resistance across the glow plugs it tiny.
"Short circuit to positive" suggests (to me) that ECU is detecting power on the preheater output line even when the ECU isn't setting it hight - but I don't entirely trust the error description to not be misleading.

There's a relay between the ECU and the glowplugs - since the latter uses a lot of current. I don't really see how the ECU could directly check the resistance across the glowplugs with the relay in the way.

I think the relay clicks when I test it with Lexia, so I don't think it's stuck (and I suspect it would have flattened the battery or melted the wires (more likely) of the relay was stuck closed - there's nothing to switch the glowplugs off in that case, as far as I can see.

So I suspect it's either a wiring fault, as Helen suggests, or an issue with the relay. Wiring it probably more likely.


I was going to disconnect and reconnect the injector and glowplug wiring the other day, but the engine was warm and I couldn't get to it without burning my hands. I'm not sure I can get to it even with the engine cold!

And talk of flattening the battery reminds me that I have a spare fusebox - from trying to resolve a battery drain fault which eventually turned out to be a bad alternator - so perhaps I should swap the fusebox and see what effect that has... Not sure it's a strong candidate though.

[tearing hair out]

OK - some more diagnostics.

Cap presence sensor - it definitely has a sensor, and a pair of magnets on the cap to trigger it. Closed circuit indicates cap present. If I disconnect the sensor from the loom, Lexia now shows "cap present". With the sensor connected, tested with a strong magnet, it always shows "cap absent". So, I think my sensor is bad (or an incorrect replacement, since it doesn't look original). I will leave it mostly disconnected and trigger it manually when I top up the fuel for the moment. I still don't know if the additive tank is actually adding anything, though I suspect it is.

I have a copy of the Bosch injection ECU technical manual, from a source that I possibly shouldn't mention. It describes "DOWNGRADED MODES OPERATION", which I assume is what we generally refer to as limp mode, as:

That's not what I'm getting - I only really have hill-climbing torque above 2000 RPM (and I think less than I should even then). So I don't think it's in an unreported limp mode.

I'll try to take a look at the wiring, etc, for the injectors and glow plugs next, I think. Though I might have limited success given the access space.

[darbuck]

How is your MAF, and have you checked the vacuum lines to the solenoids. You could have already said but I couldn't see it in the thread.

[tearing hair out]

Not sure about the MAF. I know that the swirl valve vacuum lines are working correctly (I think the diaphragm in the swirl valve actuator often fails, but mine is good) and I believe that the garage extensively tested the others. And at least some of the electrovalves are being operated according to Lexia, though whether that's showing actual state or demanded state, I'm not sure.

[tearing hair out]

Oh and there's a video on the first post which shows the air temperature and mass flow, plus 3 electro valve positions, while trying to climb a hill. I don't have a feeling for the correct values for these parameters - and I've not just come across a source that defines "normal" - but they all look pretty rational to me.

[Rp0thejester]

My issues the same as tearing hair out, my car will also go over the 2200rpm so can't be limp mode. I'm at the stage now where I do 30 mph in second gear incase there's a hill or slight incline, also in an attempt to get the engine hot enough for regeneration

[darbuck]

You need a known good 2.2 MAF reading to compare to it,Matt is your C5 a 2.2, if so can you check your MAF rate at a few different RPM rates for comparison purposes to rule out the MAF. I know they are different engines but the MAF rate should be very close.