Electro valves...

[Rp0thejester]

I know the Electro valves are important, I'm assuming they interact with the EGR. How can you tell if an Electo valve is faulty?? I'm only asking as one of them wants to suck my finger off but the other is very weak in comparison.

[GiveMeABreak]

They are used in the emissions circuit for the EGR and for the Turbo and in some cases depending on vehicle for the Air mixing units. Vacuum strength will depend on what job it is doing, and whether they are the same or different parts for different systems.

Some solenoid have a filter with a sponge like mesh that can become blocked up with deposits and this can affect vacuum pressure, so may be worth checking.

[Rhothgar]

This is a question I have been pondering myself.

One with high resistance will tend to get very hot to the touch and effectively be untouchable for anything more than a few seconds.

There is no way of testing it other than perhaps checking continuity on all of yours and then going with the one with the least resistance as being a good read.

I'll check my two easily accessible ones for you and let you know my readings. I'd not thought of this before but I do know my EGR one runs a lot hotter than the turbo one on the Xantia.

I've been looking at open cycle ratios today and have deduced more stuff about running from observing live data.

[Rp0thejester]

Thanks for the replies guys at least now I know I'm not asking a stupid question for a change

[Rhothgar]

Inspect pipes between the Electrovalves and the component very carefully for cracks if you have not already done so. Perhaps it is a general question you're asking.

No such thing as a stupid question (although I ask them all the time), only a stupid answer...

[wheeler]

Not sure if you are aware but the 3 electrovalves are the same so can be swapped around for testing.
It also matters which way around the vac pipes go so if removing them make sure you note which way they came off.
What issue are you having? they can fail in different ways sometime they stick open & give full vacuum to whatever its controlling when its not supposed to.
I remember years ago chasing a fault on a Xantia HDi that kept going into limp mode, Turned out the little vaccum pipes were all blocked up with powdery carbon type deposits, after blowing them all through with compressed air problem solved. I taken me hours to find it.

[Rp0thejester]

Well I recently taped up the air pipe, no difference, put DPF cleaner no difference in performance. Put my fingers over the 2 electro valves, one sucking super hard and one at only half with the engine idling. But there was a difference in performance uphill, she now holds 45mph up the dreaded mile long hill rather than dropping to 30mph. So was wondering if it could be the electro valves causing an issue

[Hell Razor5543]

The EGR and the turbo may be vacuum activated. On my previous C5 one electro valve was short circuited, with the result that the EGR had a split diaphragm. Once these were addressed she stopped turning on the EML so often.

On my first C5 she had an anti-pollution warning pop up every so often. Michel, when he looked, found a tiny pinhole in a vacuum tube very close to the EGR. When the pipe was trimmed back past the hole and re-fitted the anti-pollution fault never re-occurred.

[Rp0thejester]

Oh okay, so if I can find a 3 inch tall mechanic it'll soon be sorted

[Rhothgar]

OK Ryan.

So...

I measured continuity on two valves I have that are not installed. One was 3.5 Ohms and the other was 22 Ohms. I could blow through the former but the latter would not allow breath to pass.

I also measured two of the easily accessible ones on the car (Turbo and EGR) and they measured 4.1 Ohms in a warm engine bay after a 35 mile drive. They both felt warm to the touch.

I assume you don't have access to a Lexia as that would help with diagnostics.

My car seems to pull very well with no obvious issues apart from a P0402 OBD-II DTC code and from time to time a P0101 MAF

The P0402 is to do with the EGR value. Now! The EGR valve itself does not have any feedback sensors to report issues with itself but something in the MAF readings basically deduces that there is an issue even though when the MAF error code is not present.

I am wanting to remove my EGR and clean it up basically because the car stalled on two separate occasions last week. Maybe it's sticky. Maybe it's stuck open or maybe it's stuck closed.

Readings wise I had the laptop in the car today and was observing readings under certain conditions.

At idle, EGR EV is 99%. As soon as you floor it, it drops to 5% (which is the signal from the ECU telling it to shut). On the over-run, say in any gear with the foot off the throttle it drops to 5% also. I've not worked out why it would technically do that. Maybe it is to keep the engine temp up by not introducing unnecessary exhaust gases.

At idle, the Throttle EV is 79%. When you accelerate it drops. If you floor it up it drops to 5%. Same as the EGR EV on the over-run.

The Turbo EV is largely 88% and drops to 77% if floored hard.

The measured air flow on mine is odd. Idle 650mg/cp. About 1000mg/cp at 70 mph but if you floor it from 60 mph it drops to less than 200mg/cp. This could of course be a soft fault with MAF sensor. It accelerates fine so it's staying put until it gives up the ghost.

I shall measure resistances on turbo and EGR EV's tomorrow if i get a chance and measure them under throttle conditions (which might not be as revealing as if it was measured under actual load conditions).

Hope this helps.

[wheeler]

The P0402 is to do with the EGR value. Now! The EGR valve itself does not have any feedback sensors to report issues with itself but something in the MAF readings basically deduces that there is an issue even though when the MAF error code is not present.

Thats correct, these old EGR valves have no feedback whatsoever. The Air flow sensor can detect what the the EGR valve is doing by seeing how much air is not sucked into the engine. When exhaust gas is pumped in this displaces clean air so less air comes in via the air intake. Amazingly thought this system will not alert you if the EGR valve is (mechanically) not working.

The measured air flow on mine is odd. Idle 650mg/cp. About 1000mg/cp at 70 mph but if you floor it from 60 mph it drops to less than 200mg/cp. This could of course be a soft fault with MAF sensor. It accelerates fine so it's staying put until it gives up the ghost.

Yes those readings are way off, assuming for a minute the MAF is reading correctly. With the EGR system working correctly (and engine warmed up) what you should see at idle on a DW10 engine is around 230-270 mg/cp This will normally fluctuate a bit as the EGR valve should be constantly moving at idle. If you then pull the vac pipe off the EGR valve so it is fully closed this reading should jump up to 500 mg/cp. If you are seeing less than 500 this would suggest the EGR valve is stuck open or not fully closing. If you are seeing more than 500 mg/cp (and the MAF is reading correctly) this would mean extra air is being forced into the cylinder (turbocharging) when its not supposed to be.
As i mentioned above, on this system if the EGR valve is jammed closed or the vac pipe is blocked etc & not working the ECU will not alert you in any way, no limp mode & no EML. What i said above is the best way to test it without having to remove it.

[Rhothgar]

Yes those readings are way off, assuming for a minute the MAF is reading correctly. With the EGR system working correctly (and engine warmed up) what you should see at idle on a DW10 engine is around 230-270 mg/cp This will normally fluctuate a bit as the EGR valve should be constantly moving at idle. If you then pull the vac pipe off the EGR valve so it is fully closed this reading should jump up to 500 mg/cp. If you are seeing less than 500 this would suggest the EGR valve is stuck open or not fully closing. If you are seeing more than 500 mg/cp (and the MAF is reading correctly) this would mean extra air is being forced into the cylinder (turbocharging) when its not supposed to be.
As i mentioned above, on this system if the EGR valve is jammed closed or the vac pipe is blocked etc & not working the ECU will not alert you in any way, no limp mode & no EML. What i said above is the best way to test it without having to remove it.

Mighty useful information there. I think my MAF is probably not functioning 100% correct but perhaps the readings are being exaggerated because of an issue with the EGR so the thing for me to do on mine is remove and check all the pipes first off for leaks.

It sounds as though my EGR is probably stuck shut hence the higher flow readings. Once I get the chance to resolve that, I'll then see if the MAF readings improve. If performance feels OK and I have nothing to compare it with then it probably means the correct amount of air is physically being drawn in but a stuck EGR is falsifying the figures perhaps.

[wheeler]

If it was just a fully stuck closed EGR valve alone the reading would be pretty much dead on 500mg/cp & there wouldnt be any loss of power (in fact you may notice slightly better performance). As your reading is higher you may have another issue like a dodgy MAF sensor.
A vacuum gauge/pump like a Mityvac is an amazing tool for diagnosing this type of fault.

[Gibbo2286]

Poor MAF will certainly mess up the uphill ride, when mine went down had to get into first gear to get up a local hill, when replaced it was good in 4th.
Incidentally I have these sitting on my shelf if anyone wants them.

[Rhothgar]

If it was just a fully stuck closed EGR valve alone the reading would be pretty much dead on 500mg/cp & there wouldnt be any loss of power (in fact you may notice slightly better performance). As your reading is higher you may have another issue like a dodgy MAF sensor.
A vacuum gauge/pump like a Mityvac is an amazing tool for diagnosing this type of fault.

I have access to one. I was going to say I suppose it’s case of connecting to the EGR valve and testing vacuum. It shouldn’t hold any. Of course it should because of the diaphragm. It is doesn’t the diaphragm is shot.

Is there some way of assessing another way with a vacuum gauge?