C5 2.2 HDi 136 Facelift - poor MPG and no bottom end grunt

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cachaciero
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Re: C5 2.2 HDi 136 Facelift - poor MPG and no bottom end grunt

Post by cachaciero »

It is an easy job to fit a blanking plate on a 2.2Hdi and virtually unnoticeable to casual inspection, however it's against European law not just English law. On the 2.2 in my experience it makes little difference if the EGR valve is working or stuck shut, makes a lot if difference if the valve is stuck open or partially open :-).
If the annual MOT check was to check for NOX on a diesel I suspect that a non working EGR (stuck shut) would become apparent. However as I have now come to realize the EGR valve as such is only part of the system on the 2.2 as I have mentioned above, if the EGR valve is good but the intake throttle butterfly valves are not working correctly then performance consumption could be seriously affected and blanking of the EGR valve would have no effect at all.
skycat61
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Re: C5 2.2 HDi 136 Facelift - poor MPG and no bottom end grunt

Post by skycat61 »

Well I tried a new MAF but it made no difference. Interestingly the new MAF still gave a reading of 188mg/cp with the engine not running, just as before, which I find distinctly odd.

Gibbo:- yes it is time for a good poke around the engine but as I've no garage I need a good day weather wise. :)

jsp:- I've heard that people remove the EGR system by blanking it off and i'm sure it has its merits but I'd prefer to keep it standard. :)

Cachaciero:- When I get chance I will have a look at the operation of the "throttle" valve, and indeed all the rest the plumbing that is the modern engine :) Many thanks for all your input as its been a proper education. :-D
cachaciero
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Re: C5 2.2 HDi 136 Facelift - poor MPG and no bottom end grunt

Post by cachaciero »

skycat61
I am having a little Lexia problems at the mo other wise I would have been out on my C5 which currently exhibits some of the same symptoms as yours.
The MOT is up and it lost a headlight washer jet a while back which is an auto fail item so the last couple of days that has been a priority on something which is not a particularly high priority anyway.
One thing I did notice on mine yesterday is that the throttle cable is slack. Now when I purchased the car some 40K miles ago there was a lot of lag from idle and on investigation found that the throttle cable was slack, this was adjusted and all came good. So looks like its stretched again, makes me wonder if I should be thinking about another one. I don't really understand this as for stainless steel to keep on stretching in this manner would imply a lot of tension but I don't really see this. Anyway new Lexia installation then time to do the throttle then MOT During which process I will be hopefully be able to repeat some of the things you are doing.
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Paul-R
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Re: C5 2.2 HDi 136 Facelift - poor MPG and no bottom end grunt

Post by Paul-R »

cachaciero wrote:One thing I did notice on mine yesterday is that the throttle cable is slack. Now when I purchased the car some 40K miles ago there was a lot of lag from idle and on investigation found that the throttle cable was slack, this was adjusted and all came good. So looks like its stretched again, makes me wonder if I should be thinking about another one. I don't really understand this as for stainless steel to keep on stretching in this manner would imply a lot of tension but I don't really see this.
I don't think the cable does stretch. If the 2.2 is the same as the 2.0 then what I think happens is that the pedal movement is greater than the pot movement and the cable simply pulls through the clamp arrangement on the pot.

This is certainly what seemed to happen of my 2003 C5. Very early on in my ownership I felt that the performance was distinctly lacking so adjusted the cable for minimum slack. When I took the auxiliary mat out from underneath the pedal the movement was too much and so I simply put the mat back and left it at that. There may be a movement limiter on the pedal but I didn't bother to look for it.

As an aside I found that my problem was not the cable adjustment but either the MAF or MAP (I changed bother at the same time). As the OP has changed the MAF could the MAP be the problem? Does the 2.2 have a MAP?
cachaciero
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Re: C5 2.2 HDi 136 Facelift - poor MPG and no bottom end grunt

Post by cachaciero »

Hi Paul

Interesting observation re-cable I will have a closer look at that when I get in there.
Now MAP?? not come across that acronym before ah!! Manifold Air Pressure? if so yes there is a pressure sensor which from the Lexia traces that looks sensible however it really should be checked against a pressure gauge to be sure.
jgra1
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Re: C5 2.2 HDi 136 Facelift - poor MPG and no bottom end grunt

Post by jgra1 »

having a few MAP issues on the bike, was wandering around youtube and came across this chap..
I am just finishing part 2.. not sure what new stuff I have learnt but its interesting all the same ;)

skycat61
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Re: C5 2.2 HDi 136 Facelift - poor MPG and no bottom end grunt

Post by skycat61 »

Hmm, Have been having a play with the Lexia's engine actuator test functions. It tells you to run the engine for 15 seconds to build up a vacuum, stop it, turn on the ignition, and press the validate key, where upon it exercises the chosen actuator cyclically and you are invited to listen for its operation.

I tested the swirl actuator which could be heard and I know is working, but the EGR Valve, EGR throttle, and the Inlet Heater Valve could not be heard. Of course it was pitch black so I saw nothing. I will repeat this exercise this weekend with the gubbings exposed and see if the actuators are moving.

Does anybody know which of the five actuators can be seen moving?
cachaciero
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Re: C5 2.2 HDi 136 Facelift - poor MPG and no bottom end grunt

Post by cachaciero »

The inlet Heater Valve and EGR Throttle valve (inlet cold air) can be seen only by removing their respective rubber inlet pipe EGR valve itself not sure about.
Now for a wild suggestion get a Microphone on a long wire connected to your laptop mIcrophone input put the microphone adjacent to the valve you are interested in then operate the valve while recording the sound, then play the file back and see what you can hear.
I was going to suggest a stethoscope but then I reckoned most people would more likely have a PC microphone than a stethoscope.:-)
skycat61
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Re: C5 2.2 HDi 136 Facelift - poor MPG and no bottom end grunt

Post by skycat61 »

Ha ha ha! :-D Perhaps Gibbo is right too much fannying around with the kit and not enough looking! Hopefully this weekend. Thanks for the info Cachaciero :)
cachaciero
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Re: C5 2.2 HDi 136 Facelift - poor MPG and no bottom end grunt

Post by cachaciero »

Just looking ain't likely to reveal much until you know what you are looking for.
skycat61
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Re: C5 2.2 HDi 136 Facelift - poor MPG and no bottom end grunt

Post by skycat61 »

Very true cachaciero! I'm just about set up now. I have borrowed a vacuum pump from work so I can exercise the actuators with the hoses disconnected and see what the're doing without having to run the engine. As I know that the turbo modulator and swirl valve systems are working I will concentrate on the EGR valve and the two throttle butterfly valves which is where all this seems to be leading.
skycat61
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Re: C5 2.2 HDi 136 Facelift - poor MPG and no bottom end grunt

Post by skycat61 »

It was a nice weather this morning and I got round to checking out the actuators against the lexia and a vacuum pump. Both the EGR Throttle Valve and the Inlet Heater Throttle Valve are readily accessible by just undoing the jubilee clips on the hoses. Both were working perfectly when commanded by the lexia. (I connected the vacuum pump to the line connecting to the car's vacuum pump), The inlet pipes were quite sticky with black gunk.

I did not think it was feasible to open the EGR up, but listening to it, it does not appear to be working. I'm beginning to suspect that the ERG is stuck partially open and I think my next move will be to get it replaced. I can see how it being stuck might impact on MPG.
Hell Razor5543
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Re: C5 2.2 HDi 136 Facelift - poor MPG and no bottom end grunt

Post by Hell Razor5543 »

Before you replace it you might want to consider using some proper EGR Valve cleaning material (normally a spray can). What you normally do is to take the car out for a run (to get the engine nice and warm, and soften the gunk jamming the EGR), and then (obviously following the instructions) spray the can into the inlet manifold (but not over the MAF or equivalent). This can make the engine race a bit, hence why you follow the instructions. The result is that materials leaving the engine are capable of breaking down the gunk, and can restore the EGR to full operation.

I have used it, and it does work. However, it may (and, in my case, did) pop the engine into 'Limp Home' mode. I used my Lexia to clear that problem.
cachaciero
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Re: C5 2.2 HDi 136 Facelift - poor MPG and no bottom end grunt

Post by cachaciero »

As a quick test you could blank the EGR valve where it goes into the manifold two bolts and a suitable blanking plate. If you go this route I would suggest before starting that you stuff the space underneath the pipe with foam or something to catch anything that "escapes", . I reckon that behind my starter motor there is an assortment of bolts and washers and at least one 10mm socket!
Now I have been doing some digging around on my own car and found some interesting things. Problem is my new Diagbox installation is very flaky and while it saves the traces I don't seem to be able to get to them after the event. Anyway I have discovered that the Lexia lies, in that when it says the EGR THrottle valve (Manifold Butterfly) is 95% open it is actually 95% closed, The other valve of the pair (Heater) is 5% open.
This means that when the engine is cold the cold inlet to the manifold is closed and the hot inlet is open by about 5% this is fine for idle BUT it stays in this condition until something like 2500 rpm no load / car stationary!! Now I believe that the characteristics of this valve also get changed by coolant temperature and I have more work to do but if it is the case that until the engine reaches a high coolant temperature (and the indications are that that may be a very high temp) it means that for the vast majority of the rev range the inlet air is going to be both restricted and high temperature neither of which is going to be good for economy and may explain why it drinks fuel when "cold".
Frankly I am not quite believing what I am seeing and there are lots of things that need checking out but for the first time I am beginning to think that I may be getting a handle on why the 2.2 generally seems to be fuel heavy while there are some which appear to be much better in this respect.
skycat61
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Re: C5 2.2 HDi 136 Facelift - poor MPG and no bottom end grunt

Post by skycat61 »

James, thanks for the suggestion. I can't see how I could get to spray the EGR while the engine is running as this would introduce a huge leak into the air inlet system. I found "BARDAHL 9123" EGR cleaner on-line which seems to consist of a spray and a fuel additive. I may give this a go as a new EGR valve is £96 and fitting on top.

Cachaciero, Yes I'm sure the EGR Throttle Valve and Inlet Heater Valve work as a complementary pair to control the temperature of air induced into the engine. The thing is that air temperature is only measured in the MAF so one presumes this is some kind of open loop control perhaps that also take coolant temperature into account. I noticed for a warm engine my coolant temperature was about 82 C which struck me as quite cold. I would have thought about 95 C would be more like it. It does make me wonder if they actually got the ECU mapping right for these inlet system functions.

Oddly enough I had the same problem as you with the lexia, it would record traces but threw an error when it came to display them. The cure was to apply patches to bring the software up to date.