Citroen XM Forum

Hi. I am David. Just found this site. Looks good. I have had an XM 2.1TD H Reg since 1990's (approx 190K miles). Not always reliable but a great car when it is working OK. Just had another problem with the engine revs racing to screaming pitch as if the throttle suddenly flipped completely open! Just gone off for investigation.

Hi David,

Welcome to the club - plenty of useful info and help here for the 2.1TD owner!
Possibly an air leak into the fuel system causing the revs to run away?

Ken

Welcome to the Forum David and it is good to hear about another early car! Although I am not a 'diesel man' myself there is lots of expert advice available here. It would be good to see some photos! Regards, Matthew T.

Hi David, Welcome to the forum. I have a '92 2.1 SED auto myself.
Yours must be one of the earliest diesels in the country. Love to see some pics!

Hope you find a solution to your over revving.

A very warm welcome David

Welcome David,

Ive a Number of XM.. a H red Manual SED, a J reg 2.1 D Manual (currently completely dismantleing), a K reg 2.1 SD Manual, plus a couple of V6 XM too. All S1 cars.

I high rev like that could be a fueling fault, rather then an Air leak. A Diesel burns fuel (As you might already Know) Neat, and its rare on a Mechanical setup to rev up on an air leak.

It could be a Pump issue. Im guessing being H plate she has a Lucas Pump fitted.

The racing could be oil in the intake from turbo bearings leaking or an air leak as that can affect a Lucas pump, but more likely to be oil.

What is the RP number of your car and what model is it?

THATS the other thing I was trying to think about!

Oil leakage can race the engine... Cheers Will

Correct me if I'm wrong but as far as I know it's only the Lucas EPIC that can run away if there is significant air ingress into the pump. It's because the diesel is used as a hydraulic fluid to act as a fly-by-wire governor.

Mechanical Lucas DPC pumps and Bosch pumps are immune from this but one thing that can happen with a Lucas DPC is for the metering needle to jam due to gumming. Often the needle jams in the idle position and the effect is that the engine will idle but not rev. I've not known one stick the other way but it's entirely possible.

It's not hard to fix and can be done in-situ by removing the lid and lifting out the needle and cleaning both it and the bore it lives in.

Otherwise, as you both say, it's consuming its own oil. One possible cause is simply the sump being overfilled.

The turbo bearing may be failing but you would have known ages before it got so bad as to be causing a race as there would have been plumes and plumes of blue smoke. If they have got bad enough to feed the engine the smoke during the race would be biblical.

I must confess I've never known a 2.1 run away before bar an EPIC pumped one with an air leak and have heard of only one 1.9TD do likewise due to a grossly overfilled sump. I've heard of turbos failing rarely but never in such a way to race the engine.

Hmmmm.. Thanks Jim.. Im NEVER Confidant I know what Im saying, but someone always says different so I assume Im wrong..

I had a feeling Mechanical Pumps didn't run except with oil.. But wasn't confidant enough to be sure