No umph! C5 mk 2 2004 2.0 hdi manual

[chasqui]

After moving in the shadows of the forum for years, I am stumped.

My C5 is lacking power. Hardly no acceleration in lower gears and really loses speed when going up hill.

If I unplug the connector to the mass air flow sensor, a pollution fault light comes (to be expected!) BUT the car runs perfectly like a rocket.

So, I go away and order a brand new mass air flow sensor.... plug it in, clear the fault with Lexia and.... same as before.. sluggish.. disconnect the connector and it works ok! (But fault light comes on).

I borrowed another Mass air flow sensor from my other. C5, same problem.

Any ideas?

Worth noting that at no time did I ever get a service light come on, only after restarting the car when the MAF is unplugged.

Anyone experience anything similar?

Egr valve was replaced in the last year, also the throttle body.

[admiral51]

Going out on a limb as i have a bee in my bonnet about this but if it has a turbo solenoid valve i reckon the filter will not have been changed, may not throw faults up but think back to how long it has been sluggish, just recently or has it been getting slowly worse and only now you are noticing it ?

Happy to be shot down but it was something i overlooked in the Devil Car

[chasqui]

It happened from one day to the next. No warning,,

I’ll check that filter tomorrow....

Thanks for your reply

[moizeau]

Have you got, or have access to a Lexia diag tool, if it's happened that quickly it should show something.

[chasqui]

Filter in turbo solenoid valve cleaned...still the same.

Yes..have Lexia..no faults shown..

Frustrating!

[Gibbo2286]

Careful examination of all the vacuum pipes (the thin rubber ones) might be an idea, they crack and the vacuum is lost so no turbo operation. tiniest of cracks is enough to spoil the performance.

I think Marc put up an image before of the offending stuff and where it's located. (Mostly near the bulkhead on the same side as the battery)

[Paul-R]

It might also be the MAP sensor. This measures the pressure in the manifold and if it misreports a higher pressure than is actually there then the turbo will back off the amount of puff it blows. On my old Mark 1 (the Mark 2 may be different), and standing in front of the car, the MAP is a small cube device screwed to the RH corner of the radiator surround. It's then connected by a hose backwards to the manifold.

[chasqui]

Thanks for the suggestions..

Checked all pipes.. no cracks or breaks and secure tight connections. Checked pipes from inter cooler. All ok.

Running the car with the mass air flow sensor unplugged from the connector causes car to run flawlessly with plenty of power.

So have replaced the sensor and still have a problem. I have even tried another new sensor and still the same..

So,I am running it unplugged but the depollution fault message is flashing.. but car running ok.

Don’t know what to try next...

[mickthemaverick]

Thinking through your symptoms and observations the fact that it runs perfectly with the MAF disconnected and you have tried more than 1 MAF then I would suggest that maybe the MAF to ECU wiring has a problem. When connected any fault detected by the ecu may be from the loom returning a signal which is false and result in a command to reduce power which will not happen if the MAF is disconnected. So maybe the fault is in the MAF wiring thus breaking the fault condition from the return wire. In other words if a feed wire to the MAF has a faulty voltage on it, it may be reflected to the ecu when the MAF is connected. Break that connection and the return path for the faulty voltage is removed so all runs well (PM me your RPO number and I'll have a look at your wiring diagram and see if I can identify a potential culprit.)

[GiveMeABreak]

To be honest this will be mostly all guesswork - you really need to get it diagnosed first and check if there are any fault codes. No point in replacing parts without getting to the bottom of it. It is a well-known fact that cheap aftermarket MAFs are more than useless. There are a multitude of fault codes relating to the MAF and I would expect one of these to come up if there was a fault.

If you've checked the obvious including the air hoses for leaks then get it on a Lexia preferably or on an OBD code reader if you don't have access to one (not that these may always be able to read all the ECUs). Of course the engine will appear to run better with the MAF disconnected - for a short while - but not recommended for long as it will cause the engine ECU to try and compensate the fuel mixture and the engine will start running too lean / too rich which will cause damage to other sensors and components. The engine ECU is just guessing the air and fuel mixture as it will go into a backup mode to keep the vehicle running.

[mickthemaverick]

Filter in turbo solenoid valve cleaned...still the same.

Yes..have Lexia..no faults shown..

Frustrating!

Come on Marc!! I know it was late but no faults showing on Lexia!!

[GiveMeABreak]

Oh, did I lose the plot again - I did check back for a reference but was probably on another planet at the time!

So not enough of an anomaly to trigger a fault at this stage. Are you getting any rasping noises or roughness when you loose power?

I had a fault with a turbo hose - but a minute leak that was so small it took them ages to locate. This was enough to cause rough engine running, stuttering and real lack of power. A new turbo hose fixed it instantly.

[Michel]

I had a fault with a turbo hose - but a minute leak that was so small it took them ages to locate. This was enough to cause rough engine running, stuttering and real lack of power. A new turbo hose fixed it instantly.

I'm hoping this is the issue with James Hellrazor's C5 (also a 2004 2.0 HDi). It's been on Lexia countless times and has had all valves and electro valves checked and/or replaced. Not really solved the issue at all - even at a Citroen specialist.

Lexia shows airflow *drops* when giving it the beans. We've cleaned out the intercooler, made no difference. Out of curiosity I squeezed the bottom intercooler hose where it appears under the right (as you look at it) of the block while James revved the engine and there is a hot draught appears directly there, so a new pipe is on order and we will get it on the ramps, fit the new pipe and check all the underside induction pipery as it simply has to be something down there.

[Hell Razor5543]

I have got some brake cleaner, and I intend to soak the intercooler in that. As Michel said, we did give it a clean out, but what did come out was not very liquid (as nothing came out when it was taken off the car), and when we mixed engine degreaser, washing up liquid, Harpic 10X and hot water (and left it for 10 - 15 minutes) what came out was black and gloopy. Repeats (until we ran out of degreaser) had similar results, so, despite getting a load of crap out, there may still be a load in there (setting a bit like tar).

[GiveMeABreak]

Fingers crossed that might be it - mine was on a MK II C5 (DW10BTED4) 138, but it can happen to any diesel.