HDi110 auto - Slow as a Wet Week

[addo]

What have I done to deserve a rash of PSA diesel problems?
Another 8V, C5 2004. Even after remedying a slack throttle cable it doesn't show more than 89% pedal when flat to the boards.

Idles smoothly, good charging voltage, new fuel filter, no air in fuel. Just incredibly S-----L-----O-----W to get moving, almost to the point of being dangerous at an intersection. No issues starting - bearing in mind it's summer here! Owner says even under prolonged driving it doesn't show overheating.

Everything looks right on the Lexia parameters, at least when idling. Non-FAP model.

So - any suggestions on where to look? Lack of turbo boost? Restricted/faulty EGR? Blocked cat (65K miles)?

The real bastard at present (apart from overwork) is everything stays flaming hot for hours.

Thanks, Adam.

[RichardW]

Possible symptoms of a failed MAF.... check what it says on Lexia - IIRC it should read around 400 at idle, and then rise steadily as revs build.

[Gibbo2286]

I would look first at the turbo vacuum pipes, those under the plastic cover under the bonnet back right (as you look at it) a small pin hole in one of those can stop the turbo working, you need to look very closely as holes/splits in them are quite difficult to see.

[citroenxm]

Electro valve that controls the turbo waste gate on the vaccum curcuit.. its over to the right by the servo adam. Its likely to be open curcuit and in that case the turbo defaults to open wastegate hence no power.

When the electro valve is working it directs vacuum to the turbo and closes the waste gate. They are a common fail on the xantia too..

[addo]

Thanks gents. It was touted to me as a problematic AL4 auto but the gearbox is fine.

Really does sound from your comments like a lack of boost off-idle; idle boost pressure was atmosphere (give or take).

[Jeff]

Once you get going If it cruises okay'ish on the flat but struggles going up inclines and your having to cog down into 2nd (as if the revs / power has fallen away) - I would first check the MAF.

[citroenxm]

Of course it atomospheric, it wont be negative... Id say electro valve for wastegate control.. not MAF.. MAF wont have an effect on turbo spool up or even affect performace that much. Might affect fuel economy, or even throw the engine management light on..

[RichardW]

Maf went on our Picasso (2.0HDi 90) Paul - and the only symptom was a complete lack of power.....

[citroenxm]

OK.. Im happy to be corrected No problem... Cheers

[Duracell]

Changed the MAF on my wife's C5 8V 2.0Hdi yesterday - symptoms were identical - now perfect

[addo]

Non-update, but further questions.

Wastegate EV: If I bridge in and out vacuum pipes for a test blat, what will happen - engine doom?
MAF: Disconnecting it - does this cause a default map in diesels or will it completely be flat in performance?

Thanks!


Note: Last test drive with this car, I'd just backed off the pedal down to a legal limit and the rozzers came over the hill with radar hanging off the side of their vehicle. Talk about lucky!

[citroenxm]

No adam it wont hurt it the ecu will simply detect over boost and shut it into limp mode to protect it. Then you ll need a lexia to clear it all im sure you have one...

[Jeff]

Hi Addo,
If the MAF is faulty it will be similar performance when unplugged, i.e. labouring up inclines / cogging down unnecessarily...
If you have a replacement MAF you can swap / borrow, if the Mafs the problem it would be an "instant fix". My car is driving lovely now after swapping MAF's. Plenty of torque and power especially when going up hills & without cogging down.

Any scrappies out there, where abouts are you in OZ anyway?