MAF sensor readings

[yoseff]

Having now Torque Pro permanently (yup , sorry, but i installed an android radio on my C5 - function over "prettiness" ) , i realized that throttle body doesn't move most of the times. Removed it today and gave it a good cleaning , but it continues with same behavior.
I have several questions: Could it be that the normal and i'm looking at the wrong culprit of the rough engine? What would be the normal behavior of the 2.0 hdi 163 throttle body? If i move the vacuum part manually , it registers the movement, so it is either the way it is , or i have some vacuum issue.

(Un)fortunately i'm now in hollydays , so i cannot compare how it works with my (same engine) work X7, but i clearly remember that my working machine is way more smooth at lower revs...

It's difficult to maintain speeds in mine , specially the lower ones.
Am i looking at the wrong place?
Diesel filter has currently 40k kilometers , and i'm also thinking to change it. Any other suggestions on what to look for?
DPF is almost new and EGR was said to been clean recently too,
Where should i look on Diagbox that could give me some extra clues?

On a brighter note, i've already debadged the x7 and it's looking great.

Pics to be posted soon

[yoseff]

An update - Today i saw some movement on the throttle body , and the engine was way smoother. As i accelerate it stays open , but as i relieve the accelerator and then accelerate again , i see it closing a bit and then re-opening. I suspect then that it has something to do with the roughness (when not working properly) , but i'm starting to suspect that if something is wrong , it may be the vacuum valve that sends the vacuum to the throttle body (electronics seems to be there mainly to report movement) , making it close. That may be the issue. I'll keep an eye on it , and will update on how it goes.

[yoseff]

Today , did almost 200 km and in the beginning , throttle body was showing movements , but soon it stopped.
As it happens , engine response seems to be less smooth.
Starting to suspect of the vacuum valve that makes it close , or some vacuum leak. Strange that is so random on when it happens.

[yoseff]

Continuing my mission to "smooth" the throttle initial response , yesterday i changed the diesel filter. It also had 20k km, so it was more than time to change it. As i left home the behavior was quite better , and so i was convinced that it was it. At the same time i was seeing that throttle body was moving as (supposedly) should , so i continue my analysis.
Average consumption went lower (benefits of the brand new filter?) but after a while , no more throttle body movements and that "roughness" is a bit back. I'm really suspecting on some vacuum valve random problem. Is there some scheme on the valve that controls the vacuum for the throttle body? Do you want me to put the Vin here for that? It's a 2011 2.0 Hdi 163 engine.

As far as i understood, the "throttle body" actually works in conjunction with the EGR to limit the amount of fresh air while EGR is working. It also helps to have a smoother engine stop.
What i noticed from my observations , is that when it works and car seems ok , as i decelerate to put another gear (for example) and then re accelerate , the throttle body closes a bit and then reopens smoothly. That may be to smooth the acceleration, no? While at low stabilized speed with barely any accelerator , it closes quite a lot that throttle body flap and no judder at all.
What's your thoughts on that?

It would be interesting also to have the information on EGR on Torque Pro , but i suspect it may be missing some PID for that information to be displayed (or the OBD2 Dongle is too rubish for that.)

Later on will drive a bit more , let's see how the "creature" behaves today. This kind of machines seems to have a mind of their own and each day their "humor" changes

[yoseff]

Still on the chase for the culprit of the strange behavior (roughness at lower RPM's) and with Torque , i've been looking at MAF readings. At Idle , they are around 6 - 7 g/s most of the time , but after the car Idle for a while i've seen them going up to 9 - 10 g/s. Could that be a normal reading?

On the company car (Same engine, but distinct MAF - Unsure why) the readings at idle are quite a bit higher , normally around 12 g/s. I wonder witch one is ok?

Planning to give a good clean on the MAF tomorrow , to see if it changes something on the readings and the behavior. (With MAF cleaning spray, of course , so it gets done properly)

Is there any oficial information about what should be the normal readings on the 2.0 HDi 163 MAF ?

[darbuck]

Your maf for the first car looks ok assuming it's at idle the second one is high for idle. Typical maf readings on any car is between 2 and 7 at idle higher than that indicates an issue but is relative to rpm. The higher the rpm the higher the air flow rate. Your fuel rail pressures look more problematic to me and could be the route of your issues. The second car seems like it has a much lower fuel pressure so it might have a leaking injector or two. You need to get a proper diagnostic session with lexia.

[yoseff]

Your maf for the first car looks ok assuming it's at idle the second one is high for idle. Typical maf readings on any car is between 2 and 7 at idle higher than that indicates an issue but is relative to rpm. The higher the rpm the higher the air flow rate. Your fuel rail pressures look more problematic to me and could be the route of your issues. The second car seems like it has a much lower fuel pressure so it might have a leaking injector or two. You need to get a proper diagnostic session with lexia.

Thanks for pointing the Fuel rail pressure. Didn't spot that one. There's a a lot we can read in numbers when we know where they should be , and that's not my case yet

That's a print-screen , so the numbers were "at that moment". There's a bit of oscillation on both cars. First one's MAF once in a while goes up quite a bit, sometimes up to 10 (Rare, but happens) , so what i mentioned are the average values at idle. The fuel rail on the second one also goes a bit higher sometimes.

The funny part is that the one with the issue is the first one, but i'm realizing i see "worst" numbers in the second one.
Basically it has a "rough" acceleration , a bit too much impetuous in the initial rpm's and it's hard to mantain low constant speeds - it jerks quite a bit. Also noticed that when decelerating it doesn't have so much initial engine braking - a bit like if it was still a bit accelerated... Wonder if it is another symptom connected to the roughness.

Need to see it with the Lexia (No related codes till recently). Data is also probably more reliable than with the ELM clone. The Bluetooth just makes it more convenient to keep an eye on the numbers. Wish there was an Android Lexia that could connect by Bluetooth.

As a curiosity, one car is from 2011 and other from 2010 , both with the 2.0 Hdi 163 engine , but MAFs are different in brand and design. Could that be a replacement or can be like that from factory?

2010 has one like this:

2011 has one like this:

[PaulC5]

Our 2007 C5 now has a Continental make MAF. With the engine not running and the dash lit up it gives a reading of about 4, I thought it was faulty and bought a new one and that is the same so if you find this just ignore it. Searches found other cars were similar so not just on our car. Our 308 shows 0 with the dash lit up . The original C5 one was a Siemens and the new one Continental who seem to have taken over the business. On idle it starts up about 11 dropping to about 7 once warmed up.

[darbuck]

Just to clarify Continental is now VDO formerly Siemens. these cars are very fussy. even a few milliamps can make a difference to how the ECU interprets the signal received from the instrument. in my experience it's best to stick with original parts when you buy sensors especially mafs, they can cause all kinds of running issues. Siemens are the most reliable sensors you can buy so if they are available and affordable I would be buying them. Just to be clear I am not and have never had any affiliation to Siemens I'm just speaking from my experience I presume they are the same quality. As you say stick it on a Lexia, I too wish I could get a blue tooth lexia.

[yoseff]

After a good cleaning , values lowered a bit at idle , sometimes going to around 5 g/s , but it continues to oscillate up to 7 / 8. Probably will need a new MAF in the near future...
Didn't try yet to clean the one fro the working car (the 2010) Do i send the MAF cleaning fluid inside it? I don't see any other way. And yes , i agree that original parts are the way to go , specially on sensors.

[Rp0thejester]

Are you sure it's the MAF? Just disconnecting should see better performance. If not then in could be something further down the line.

[yoseff]

Are you sure it's the MAF? Just disconnecting should see better performance. If not then in could be something further down the line.

I'll try disconnecting it tomorrow, to see the result

[PaulC5]

As well as MAF values, have a look at the MAP values. The MAP should be atmospheric pressure before starting the engine and once running using the accelerator pedal the values will change. If not then the MAP and/or its tapping point might be bunged up with carbon. Whilst not important, if you can, get the values in bar or mbar rather than psi.

Whilst not mentioned in the posts, I assume it is a C5 you are having problems with.

[darbuck]

To clean it you take it off the car and very carefully and liberally spray the sensor itself. Make sure you don't touch the hotwire with anything solid it will almost certainly snap if you do. Gentle is key

[Doo]

As a further, the MAF also controls the use of the EGR on a diesel engine so if you are unsure of the state of it, might be worth a look as they can & do suffer from a build up of carbon.

On that note, when I did my wife's 2007 C4 1.6hdi engine not that long ago, I was pleased to note the EGR was if not immaculate, then as close as you can get for a valve that spends it's life in the exhaust system.

I am pleased to announce I am certain this is due to the prolonged use of BP Ultimate (or it's equivalent) diesel. That and regular oil & filter changes.