Xantia 1.8 16V Engine running erratic

Unread post by **howardaskew** » 27 May 2008, 18:24

My wife's Xantia runs a bit rough every so often.
The accelerator cable is a bit heavy for my liking.

The symptons are like this (take today)

Car starts but refuses to tick over so forever stalls.

Car after a long journey may then decide not to tick over at anything less than 3000rpm!

The spark plugs are champion and previously they were 3 pronged bosch plugs. But this problem was there on the Bosch also.

Most days the car runs fine but any advice anyone?

It is annoying enough to want to get rid of! (That and the very stiff undoable accumulator sphere!)

I don't believe 3 prong plugs give better running just longer wear characteristics after all there is only one spark!

I look forward to suggestions of advice. thank you

Just changed to 110HDi C5 it is nice car to drive but somehow less of a drivers car!

_kid_ · Unread post by **_kid_** » 28 May 2008, 00:54

Mine is the same engine. (Not many on here with this engine)

Try the simply (read easiest) items first

Have you taken the stepper motor out and cleaned it, as these can clogged up with gunge and also clean throttle body and all nearby areas and hoses, this may work.

Also i believe the coolant temperature sensor (the green coloured one near the thermostat housing) can cause this sort of problem too.

I had occasional over-revving and stalling (mainly when cold) and cleaning the stepper motor has cured it completely- in fact the car has not stalled since i cleaned it about six months ago, and idles perfectly.

Btw what sort of mpg do you get in town driving, i find mine thirsty,

Unread post by **CitroJim** » 28 May 2008, 08:08

Another cause of these symptoms can be manifold air leaks allowing unmetered air to enter the engine. Check everywhere south of the throttle butterfly to the engine, not ignoring any pipes that connect to the manifold.

I don't know these engines well and I'm not sure if they use a MAP or MAF Sensor to measure airlow to set the mixture. If, like the 8V 2.0L engines, they use a MAP sensor, this may be at fault or more likely, the pipe from the manifold leading to it. This pipe can perish and let air in and upset the mixture. Sometimes the leaks are bad enough that you can hear them hissing.

Failing all of that, find someone who can perform a diagnostic on the ECU to see if any faults are stored and to check the operation of various sensors under running conditions. If you're near to me, you are more than welcome to a diagnostics session.

One way to tell if the ECU may have a fault stored is to observe the engine management light. If it goes off immediately the engine starts, this means no stored faults. If there is a delay before it goes off, it is likely faults are stored.

I expect fuel economy will improve once the underlying cause is found

Unread post by **howardaskew** » 28 May 2008, 10:09

Thank you for the advice chaps.

I never realised there is a throttle stepper motor.

I will clean motor if I find one and check all the hoses for leaks.

If that does not cure the problem then I will take it for a diagnostics check.

How much do you charge for a diagnosics session Citrojim?

Does anyone know of a good place for Citroen diagnostics near maidstone in Kent?

AndersDK · Unread post by **AndersDK** » 28 May 2008, 18:52

The throttle position sensing potientiomer (opposite to the acc cable fitting) is known to cause strange symptoms when they wear out near the bottom position, where they always do most of the work.

A flat device with a 3-wire cable connected. Can be checked simply with an ohm-meter on the cable - unplugged. Something like 5K ohms total resistance between 2 wires - and a smooth varying resistance from the middle wire to one of the other wires. Its quite often easy to recognise a "hole" in the resistance element during movement of the throttle.

These TP's tends to be standard devices where a single type will fit a very large range of makes & models. Pricetag in the region of £30.

deian · Unread post by **deian** » 28 May 2008, 20:26

It's going to be either the TPS as anders said, or the MAS/MAP sensor especially if it has poor fuel economy too. A bad air sensor would probably show hesitation /flat spots too.

The idle issues seem to point towards the TPS. I would doubt the idle control valve would have ecu take control when it warm and rev it to 3000rpm.

Try wiggling the wires around the TPS and the MAP/F sensor when it's idling, you may have to just give the TPS a gentle knock (medium strength with screw driver end) where the cable wraps around and spins the throttle butterfly open just to see if there is any free play in the metal contacts.

Unread post by **howardaskew** » 29 May 2008, 10:18

Regarding MPG it has fallen over last 18 months.
I never get below 30mpg regardless of how bad traffic is. Central London driving and usually around 36mpg and can be as high as 40mpg.
I have been getting 32-34 of late but I put this down to age.
I think all cars that drink fuel will be uneconomic to drive soon.
I wanted a C3 HDi that has £35 road tax and 67mpg but could not find a good one below £3000.
So I bought a C5 HDi 110 for 2200 with 122,000 miles.
I think in 2 or 3 years time the 100mpg vehicle will be preferred option.
It will be a good way to save money or maybe all this biodiesel mix will make the unscrupulous use red diesel mix!