So I decided to start a new thread (from this one: Car cutting out after start-up when turbo actuator arm is connected. - Jaguar Forums - Jaguar Enthusiasts Forum) because the title doesn't seem to be that relevant anymore, and the symptoms have changed, and I think I've narrowed down the problem a bit more now.
Basically the car is running really poorly, stuttering and occasionally cutting out. And definitely worse at low revs.



Today I took some readings with the EGR plunger motor (image above), connected (first image below), and then disconnected (second image), and it seems pretty clear that when it's connected the car is reading less air going into the manifold, close to 50% less. And the MAP reading is a bit lower too Maybe 4-5 kPa on average. But it sorts itself out at higher revs.










This tells me that my MAP and MAF are reading the correct values, but that something is going on with the EGR plunger. Perhaps it's letting some exhaust gas in through the EGR when it's not supposed to, reducing the amount of good air that goes past the MAF, or perhaps it's not opening when it should (to let some exhaust gas in), and so the car thinks it should have more air + exhaust mix when really it just has a lesser amount of clean air, and so it gives too much fuel. It does also sometimes rev up a little bit by itself, maybe from 750rpm to 950rpm for a second.

But the bottom line is that the MAF sees less air when the EGR plunger has power.
The problem also doesn't come back immediately when I reconnect the connector, it's like I have to rev the car a bit, perhaps the plunger opens but doesn't close properly?

Does anyone know how often this plunger should open? Is it only at certain speeds, or above certain revs? Or above a certain speed, and below certain revs, like when the car is cruising?

I don't think the butterfly valve side of the EGR is the issue since it's held open by a spring, and it needs vacuum to close it, so it's unlikely this would cause the MAF to read less air coming in. And I cleaned the EGR last week. Plus I can hear it flapping away when the car shuts off.

Come to think of it, the plunger is held closed with a spring, and needs power to open it, so that rules out it being stuck open, unless the spring isn't working correctly.. But it seemed OK when I looked at it. THe spring wasn't weak, or broken or anything.

I took the car out for a little spin with the connector disconnected, and the car ran fine, boost and everything, until the car eventually realised that the connector was off, and then it obviously gave me a gearbox fault (couldn't calculate a torque value), and so it cut my boost. But this just shows that the car can run fine, and it's definitely getting enough air/fuel/boost, etc.

Thoughts?

 

So I finally got around to getting the multimeter out today, and when I put it on the output from the EGR it was reading 0.20v when the car is running good at idle.
After revving the car a bit the EGR output jumps up to ~0.63v and stays there and that's when the car starts running poorly. It did indeed suggest that the EGR is opening slightly and not closing properly. It could also be a faulty signal, but I don't know what the reading is supposed to be, so I can't be sure.

I confirmed this by putting a quick blanking plate on the EGR and the car now runs perfectly.
Looks like it's time to get a new EGR, since my car likely won't pass the NCT (Irish MOT) without it. They're quite strict on emissions, and they even plug into the OBDII port to see if anything is amiss..

 

Unfamiliar with the Diesel variants, but yours being a 2.2 engine it appears to have an electronic EGR valve assembly, compared to the 2.0 engines that are a slightly different EGR valve and position sensor setup.
I am assuming the EGR valve needs to send back accurate valve position information to the electronic control module, which possibly relies upon a resistive potentiometer in the EGR assembly.

If it is anything like the TPS sensors for throttle body position, they can suffer from a noisy or 'dead zone' where the sensor wiper contact commonly rests or operates on the carbon track.
If that is the case, you could end up with variations in the ECM's understanding of the EGR's physical opening angle.
If you can manually operate the valve position on the car or bench test, I suspect pins 2, 4 and 6 on the EGR plug possibly are the positional sensor where pin 6 is the variable resistance output, and measuring ohms to pin 2 (negative reference rom ECM) and pin 6 (positive reference from ECM).
I would hope that you might find the resistance change is erratic in that zone, which might explain your symptoms.

 

It looks like 2 & 4 are power (12V) and ground, 6 is the output, and 1 & 5 are the inputs, but I'm no an expert by any means, and all really I only know is what's on the diagram below.
But, activating the EGR is one of the problems, since the only way to do it is to take off the back cover and rotate the gears (like how a brake piston works) but the electronics are on the cover, and it also hold the gears in place.
I'm guessing it's some kind of feedback circuitry inside the cover, because it's basically 5 wires going in, and only 2 connections on the inside that go to the motor. As in the second image below..

 

Hmmm....good photo!
What is the part I have circled?

 

I think that's the position sensor for the vacuum operated butterfly valve, to send less "good" air into the manifold.

 

The gear cover plate you removed has a 5 pin connector into it, two pins will couple into the copper tracks that then reach across to the motor terminals visible.
The remaining 3 pins must be to a sensor of some kind that is incorporated into the plastic framework inside that lid.
What that is sensing and how has me puzzled.
None of the gears appear to have cams, nor have obvious magnetic encoders for a inductive or hall effect pickup....very puzzling.

I have a suspicion that you might want to check that butterfly position sensor to see if it has any resistance instability in the position it would normally be held in when you are idling and getting the issues. If removing it you might need to first check if the fixing points are slotted for a mechanical alignment, or if just a round mounting hole and no rotation adjustment.
If is is dodgy you might be able to find just the sensor based on any OEM casting part numbers on it.

I am mindful that I don't want to be leading you down a garden path here, so just suggesting non destructive checks for what might be mechanical feedbacks that could be creating instability in the engine management.

 

I'm thinking it might be that it gets the power and ground from 4 & 2, and then the inputs 5 & 1 use them to vary the amount of power that goes to the motor. And then the output, 6, just measures how much the control voltage changes inside, like when the plunger reaches the end of its run. It might just be a constant-current circuit/transistor inside it or something.
Or I could also be talking through my ****..
But yea, I was a bit surprised when I saw 5 wires going into the cover, and only 2 connections inside..


But the car seems to run fine with the blanking plate installed now, so I'm thinking that the butterfly valve isn't an issue.
Although I think I'll either have to try to tighten the spring on the plunger side of the EGR, or else just buy a new EGR to get it all running as originally intended, since there might be some discrepancies when the computer thinks there's a certain amount inert air (exhaust) going to the manifold when there's not. And so, the MAP and MAF might not agree with each other.

But I doubt I can find spring for this type of EGR, as there doesn't seem to be much info on these EGRs anywhere, so somebody selling spare parts for them is unlikely..

 

So, I think I've finally solved the issue.
Yesterday I took off the EGR to have a look at the spring in the plunger and I was surprised at how easy it was to get to it. Just pop off the cover, and remove the 3 screws underneath:



The spring pops out quite easily:



I cleaned up inside and put the spring back in a bit tighter and put it back together, and the car ran a little better, but not much.

So today I went back and didn't bother removing the whole EGR/intake manifold, etc, instead I just clipped off the back cover and removed the screws:



And tightened up the spring as much as I could:




I think I have tightened it a full revolution now, half each time, and the spring is in the correct notch on the plunger. I don't seem to have put it in the notch the first time since I only tightened it half a turn.

It's much easier to do it this way, rather than having to take off the whole EGR, and the intake manifold, to get it out. I'd say it was about a 5-10 minute job to do it this way.
And the car seems to be running perfectly now.

The revs are the same when idling (around 750rpm) although it sounds like the car is revving slightly faster, but it's probably because I've gotten so use to hearing it spluttering slightly for so long that it seems this way.

I don't know if the spring is supposed to be as tight as it is, or if it has stretched over time, because I've never seen the interior of these kinds of EGRs before. I could possibly have made it too tight, and perhaps the EGR won't even open, so it could be the equivalent to blanking the EGR, and if this is the case then I might fail the NCT on emissions in a few months. Or I might get a light on the dash at some stage for an emissions issue. I suppose I won't know until it happens, and if that's the case I'll probably have to get a new EGR valve.
But until then I'm happy to have the car running properly again..

I can definitely rotate it with one of the gears on it, and it seems like the EGR will open a little, but it definitely has a more sudden, sooner, stop than it used to, I assume from the spring being as tight as it can possibly be.

Hopefully this will help someone in the future, and if anybody is bored and decides to open their EGR like this it would be interesting to see how much tension is on the spring on a different EGR. For reference.

 

That will definitely be interesting to see how you get on.....

Also I got to make out the numbers on the sensor module visible in these pictures 988F98989 is a Ford throttle position sensor.

Similar to (but not quite the same as) the TPS on my 2.1 V6.
They do eventually get a wear point in the carbon track (in the commonly active portions idle and just off idle) that can give incorrect positional readings back to the ECM when worn.
It should be obtainable as minimum part you can easily source on its own and replace if/when the time comes.