2008 C5 2.0Hdi Auto Niggles

[Jadblobs]

Hi, I've owned my C5 since November just gone. Very please with it although there are a few niggles I'm hoping someone might have come across.

First is, there seems to be a resonance vibration from the engine when at 1750rpm In any gear. Most noticeable at 60mph when it's in 6th, its just a constant vibration you feel through the car once above these revs it smooths out. I though it was the gearbox, but if you slowly build the revs up in neutral it becomes evident once you hit 1750rpm. A garage have checked but can't find anything wrong. Occasionally it will come up with pollution system faulty if you need to accelerate hard and will what feels like turbo pressure loss, not limp mode. Switch of and on and it drives fine and a few days later the engine light will go out, fault code points to fuel pressure sensor. Unsure if the two are related.

Apart from this the car always starts never had any major issues. Car only does about 40 miles a week normally, only use it for family runs as I use my wife's c3 for work. Anyone had a similar issue? Thanks for your help

[paul.h]

Could you put the fault codes on here since it may help. How many miles has the car done ?

 

I have put your car details on your signature to save you needing to mention it every time you start a new topic. If these are not correct you can edit them by going to your profile.

[coastline taxis]

What size engine is it

[paul.h]

It is the 2.0 hdi 6 speed auto C5 X7.

[Rookie2]

Recently done a Megane which was cutting out, rough tick over, going into limp mode, switch off and it would reset, pollution fault reported, started first time everytime.

 

Turned out to be MAF sensor, cheap copy from ebay did not work, had to buy a Siemens at 120.00, problem soved.

 

Before spending fortunes, get a can of electrical cleaner and spray the element of the MAF sensor. Do not touch it with your fingers as the static in your body can blow it. If possible blow the element dry with a compressor air line.

 

You could also try unplugging the MAF sensor altogether and see if that alters ths symptoms you are getting at all.

[Jadblobs]

It is the 2.0 hdi 6 speed auto C5 X7.

Yes it is.

[Jadblobs]

Recently done a Megane which was cutting out, rough tick over, going into limp mode, switch off and it would reset, pollution fault reported, started first time everytime.

 

Turned out to be MAF sensor, cheap copy from ebay did not work, had to buy a Siemens at 120.00, problem soved.

 

Before spending fortunes, get a can of electrical cleaner and spray the element of the MAF sensor. Do not touch it with your fingers as the static in your body can blow it. If possible blow the element dry with a compressor air line.

 

You could also try unplugging the MAF sensor altogether and see if that alters ths symptoms you are getting at all.

Have tried this and it made no difference. Edited March 6, 2017 by Jadblobs

[Jadblobs]

Could you put the fault codes on here since it may help. How many miles has the car done ?

 

I have put your car details on your signature to save you needing to mention it every time you start a new topic. If these are not correct you can edit them by going to your profile.

Thanks, I'll try and get codes later, it's done 113000 with full history.

[paul.h]

If running the engine with the MAF unplugged made no difference, then this could be a sign the MAF is faulty or the car is already in limp mode before the MAF is unplugged. Since the MAF has been unplugged you will have stored fault codes from that. If possble the codes should be read and then deleted and then read again after running the engine.

[Jadblobs]

Car was running fine no codes stored, engine, engine light or limp mode. When unplugged engine light came on, fault code for Maf, drove car for 20min, ran fine, reconnected and cleared faults, ran exactly the same. Car doesn't go into limp mode at all, can still get to 80-90 if I wished and will still rev to. 4k, just low on power. Pull over and switch off and on, power is restored.

[Rookie2]

Jadblobs

When the car is running at tickover, do as Paul suggested and pull the plug off. You should hear a quite discernable change in the engine note when it is unplugged.

 

As I said, I have just done a megane that had exactly the same symptoms and yes, when the customer stopped and switched off it cleared the fault. No codes registered on diagnostics but the MAF sensor was faulty.

[Jadblobs]

Maf don't do much, but having read else where, it only works in line with the egr as diesels don't really need a Maf. It works differently to petrol, as yes soon as you unplug it it will run rough. I've got it booked in for a service so I'll get the to plug in lexia and have a good look. Thanks for your help and I'll relay the outcome. Edited March 13, 2017 by Jadblobs

[Rookie2]

Hi Jadblobs, I dont know who told you the MAF dont do much on a diesel, because they are wrong.

[Jadblobs]

Hi, Google it there is loads of info on it. I tried it on my misses 1.6 hdi c3, it made no difference on her car and hers runs perfect.

[Rookie2]

Hi Jadblobs

 

Here is a quick write up about MAF's, I know they are refering to BMW but much of it is pertinent to all diesels.

 

Also when they mention that an out of spec MAF will produce little more than a rich running engine, just remember that on Citroen cars we have Particulate Filters that control the ECU from information they pick up about fuel  ratio's, so though a rich mixture may not matter for some manufacturers, it certainly does for Pug Citro who's DPF is designed to negate rich fuel mixtures.

 

Anyway, here's the write up for BMW.................

 

If your BMW engined vehicle suffers from poor performance from below 1800-2200rpm it is most likely due to an out of spec maf sensor. 

This can happen from as low as 30k miles.http://synergytuning.co.uk/75Zt/maf3b.jpg

The MAF sensor is fitted in the inlet duct on the outlet of the air filter and measures the mass of air flowing into the engine. In theory, therefore, the ecu can inject the correct amount of fuel for the amount air going in and thereby meet the latest emission regulations. Its located on the duct just behind and to the right of the oil filler cap. The connector is obscured by the overlapping top of the air filter housing lid. (more maf sensor info here)

In practice, the Bosch sensor is notoriously unreliable and drifts out of spec as it ages. This is understandable, since the sensor element operates at 200^oC and semiconductors deteriorate at these temperatures, even though Bosch seem to have overlooked this fact!

http://synergytuning.co.uk/75Zt/2maf.jpg

The result is that the ecu most commonly receives a reduced signal, and because it cannot know if the signal is reduced from say a clogged air filter, it must assume it is correct. 

 MAF sensor degradation NEVER shows up on standard diagnostic tests this means your dealer will NOT SPOT IT! (dealers rely too heavily on fault code readers)

(Complete Maf failure  - where it is short or open circuit will show up and will also light the engine management light on the dash.)

The maf sensor has most impact below 2500rpm.  In the 1000-1700rpm range, where the turbo is not generating much boost pressure so there isn't a surplus of air, it is difficult to meet emission regulations without accurately metering the air flow so the maf signal can have a very pronounced effect on the performance.

Above about 1800rpm, the turbo starts to become effective and above 2500rpm there is often a surplus of air and so the ecu does not need to rely upon the maf signal quite as much. It can simply be programmed to limit the maximum amount of fuel to control the torque.

So if the maf signal has fallen due to a degraded sensor, the first and most obvious sign is very sluggish acceleration when pulling away from rest.  This heart stopping delay pulling onto roundabouts and into heavy traffic is downright dangerous.

It also makes the car tedious and unpleasant to drive at speeds below 2000rpm because the fairly sudden fall off of torque requires more gear changing.

 Auto models are just as bad, needing a lot of throttle to get moving or change down, and some even stalling when you pull away, with overall sluggish gearbox operation and even worse mpg as a side effect.

You will also often find that maximum torque occurs at much higher rpm than intended. Possibly not until 2500rpm, whereas on the 75 & ZT it should be around 2000rpm, and on the Freelander, around 1750rpm (thanks to its variable nozzle  turbo).

In about 25% of cases, the signal becomes elevated above normal and this will overfuel the engine at low rpm. Because this doesn't result in poor performance, it is all too easy to assume the maf is working okay. Very poor mpg, exhaust smoke, exhaust reeking of diesel when idling are tell tales of an overfuelling maf. For the same reason, correcting the excessive signal & hence the overfuelling may reduce the performance so some owners moan when this happens. Its their choice to stick with the existing maf and drive a thirsty smoking, mot failing diesel, or do someting about it. The Synergy 2a cannot reduce the signal so an overfuelling maf must be replaced with our Pierbugh one.

So to sum up, the maf signal must be correct for optimum performance AND economy. You can't just stick in any old maf, a  cheap Ebay clone or ones sold for BMW cars and expect to get a good result.  Also, no tuning product - box, chip or remap  will work properly if your maf sensor is out of spec, so if you are disappointed, after having spent £100s on such a product, look to your maf sensor.

You can get a good idea if the maf is the problem by simply disconnecting it and going for a drive. The performance will be much better if the maf is out of spec. However this is not a 100% reliable test because an out of spec fuel rail sensor can also produce  weak maf like symptoms. The TD4 suffers more from this due to water ingress into the wiring and sensor. 

Disconnecting the maf also disables the egr system so some of the improvement is due to this, though only at a constant speed. (When accelerating the egr system is switched off)

Many owners have sold their pride & joy because they were sick of the poor performance when a Synergy (Ronbox) 2 will cure the problem and boost performance to uptodate levels.

FREE TIP: Save yourself a fortune and sort a maf problem out yourself. I hear regularly from owners who have been charged upto £2000 by incompetent garages who could not diagnose a weak maf and replaced just about everything else!!!

NB: DO NOT FIT PIERBURGH MAF 7.22684 09.0 with or without a Synergy (Ronbox) 2 as this ONLY for BMW vehicles. I also do not recommend the 7.22684.11.0 maf now produced as a direct Bosch alternative as the results are still not as good.