Xantia 1.9 TD normal idle speed?

JamesQB · Unread post by **JamesQB** » 13 May 2007, 21:52

Hi everyone, got myself a Xantia 1.9 TD a few weeks ago, first diesel Xantia for me. I like the car a great deal, but just wondered if the idle speed was a bit too high.

When fully warmed, it idles at around 10500rpm. I thought diesels idled at lower rpms than petrols, and most petrols seem to idle between 750-900rpm. Is that wrong?

As I'm new to diesels, can anyone tell me what might be causing excessive fuel consumption as it doesn't seem to be doing too well on the mpg.

Thanks,
James

AndersDK · Unread post by **AndersDK** » 13 May 2007, 22:54

Diesels runs much the same idle revs as petrols.
Because of the high diesel compression ratio you also have an inherent resulting vibration, which worsens at lower idle. So diesels are not normally run at low idle revs.
A good rule of thumb is some 850-900 rpm warm idle.
Whereas petrols would be some 50-100rpm lower.

A very common problem is the coldstart system which fails in stuck coldstart position. This system makes sure the diesel engine is as easy as possible to ignite in coldstart conditions, at the same time preventing engine stalls from cold running instability.
This is done by increasing the idle revs a bit, and modifying the injection timing a bit.
Contrary to petrol engines, the diesel coldstart system does NOT enrichen the fuel.

From this its quite obvious you have a problem with the coldstart system. You dont say what buildyear of your XantiaTD.
The earlier diesels had a coldstart cylinder in the thermostat housing - with a bowden cable operating the modifing lever on the diesel pump.
Later diesels have vacuum operation by electrovalves.
Should be fairly easy to recognise, as there will be a vacuum hose from diesel pump to an electrovalve somewhere. Either you have split vacuum hoses, corroded electric contacts on the electrovalve - or the valve itself has come to its end of servicelife.

While you are there - check the diesel pump throttle lever is pulled fully home when you buttom the throttle pedal (NOT with engine running !).

Unread post by **Peter.N.** » 13 May 2007, 22:58

1050 does sound a bit high, 800-900 is more usual, but there is usually a critical speed that transmits the minimum ammount of vibration to the car. If your car has a mechanical fuel pump it is quite easy to adjust it, but if its post '96 with an ECU, you cant.

Unread post by **Peter.N.** » 13 May 2007, 23:00

Sorry Anders, we must have been typing at the same time.

JamesQB · Unread post by **JamesQB** » 14 May 2007, 19:56

Thank you both for your replies. The vehicle was first registered in November 1996, so if you could say which system it's likely to have regarding the coldstart I'd appreciate it a lot.

As for my perception that it isn't doing well on fuel economy, other than the usual suspects like air filter, is there anything else in a diesel that can be the culprit? I expect diesels have inline fuel filters like petrols, so that could be another suspect?

I'm off to check the throttle lever right now with my wife in tow to do the pedal pressing whilst I check under the bonnet. I'll let you know the result.

Unread post by **RichardW** » 14 May 2007, 20:11

1996 is most likely to be the cable from the thermostat housing rather than the vacuum solenoid. It's easy to check - just look at the back of the injection pump, you will probably see a cable running to the stat housing.

Xantia TD is not great on fuel. Expect high 30s around town, low 40's on a run - if you don't exceed 70 mph. At a sustained 3000 rpm (75mph), both my Xantia TD's have returned just the wrong side of 40mpg. I get just over 40 in my 30 mile commute which is mostly open road running.

Xaccers · Unread post by **Xaccers** » 14 May 2007, 21:58

Ouch those are low mpg's alright!
My 95 Xantia 1.9TD used to be able to get near 50mpg on motorways/country roads.
Once managed 816 miles on a single tank

My 97 estate used to get over 40mpg and that was bombing up and down the M25 each day (90 mile round trip) normally over 80mph

Now my 2.1TD, that's worrying me as it's doing 33mpg at the moment, but the majority of journies are about 10 mins at 30mph.

Unread post by **CitroJim** » 14 May 2007, 22:12

Xac wrote:Now my 2.1TD, that's worrying me as it's doing 33mpg at the moment, but the majority of journies are about 10 mins at 30mph.

I get nearly that from an Activa

Admittedly with a featherweight foot.

You must have an awful lot of lead in your boots Andy!

Time for some serious diagnostics methinks...

Unread post by **Peter.N.** » 14 May 2007, 22:50

My 2.1 td XM estate averages 40 mpg+ and on our Scottish trips will do well over 50, but I am old and dont drive all that fast!

weety · Unread post by **weety** » 14 May 2007, 23:35

my old xantia hatchback (m reg td) did 45mpg..... but my newer estate with air con) struggles to get past about 35mpg.....never mind though i am about to convert it to run on veggy

KP · Unread post by KP » 15 May 2007, 08:23

i got 41.26mpg from the last 700miles worth in my current 2.1td

Once i sell it and go back to a 1.9td it will be veggie oil being used again so MPG wont concern me that much, especially on my new 15minute commute

Xaccers · Unread post by **Xaccers** » 15 May 2007, 09:55

Yup, I really think mine has a fuel leak somewhere!

TehAgent · Unread post by **TehAgent** » 15 May 2007, 23:42

I'm going to test how far i can get on my car, it should be about 45 - 50 miles on 5 litre's at the moment, i got two Jerry cans in the boot, may as well fill a Jerry can and run the car till its empty, then put 5 litre's of fuel in it and fill the Jerry can up, then run the car till its dry again and take note of how many miles i got out of it....

Watch this space for a update.

jeremy · Unread post by **jeremy** » 15 May 2007, 23:56

Much easier to fill it right up, set the trip recorder or note the mileage, run it for a while and then fill it up again, noting the amount of fuel added and the mileage when you fill up.

Its not really a good idea to run cars out of fuel. Diesels require priming (older ones have to be bled - Citroens seem to be self bleeding when primed. There is always the risk of muck being drown up from the bottom of the tank which seems to happen to some people, and if you have a Roto-diesel pump or derivative it relies on fuel to operate the internal governing mechanism and the thing can suddenly rev when air gets into the pump.

tomthered · Unread post by **tomthered** » 17 May 2007, 12:36

How do you get a diesel to run on veggie oil, anyone got any info please?