Citroen AX - idle goes down

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tanov
Posts: 7
Joined: 06 Apr 2004, 15:37

Citroen AX - idle goes down

Post by tanov » 06 Apr 2004, 15:46

When the car is warm if I push the accelerator and release it
the idle goes very low as if the engine will stop.Also is difficult
to start again.But if it is cold there is no such a problem except
the chocking and slow acceleration when the accelerator is pushed down.I 've replaced the throttle potentiometer and electronic ignition unit (amplifier).

mbunting
Posts: 712
Joined: 21 Dec 2001, 16:19

Post by mbunting » 06 Apr 2004, 17:12

Had very similar problems on 1.0i AX, it was the coolant temperature sensor.
It refused to start when warm, after about 20 minutes, you could coax it into life, but get practically no power out of it.
From cold, it was absolutely fine whatever the driving conditions, until you turned it off when warm !

tanov
Posts: 7
Joined: 06 Apr 2004, 15:37

Post by tanov » 28 Apr 2004, 16:20

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by mbunting</i>

Had very similar problems on 1.0i AX, it was the coolant temperature sensor.
It refused to start when warm, after about 20 minutes, you could coax it into life, but get practically no power out of it.
From cold, it was absolutely fine whatever the driving conditions, until you turned it off when warm !
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
So I have to replace the coolant temperature senso?
Is it cheap?
I think that if there is a fault in this sensor it will say to ECU
that the car is constant cold or constant worm?But you thing that
there is a middle fault:-)?

mbunting
Posts: 712
Joined: 21 Dec 2001, 16:19

Post by mbunting » 28 Apr 2004, 21:09

If the sensor is faulty, the ECU will know about it, and will be using default values, which are good in some conditions, and bad in others, they're there to help you start and run the car.
There will be no indication on the dashboard of a fault, however, a cheap compatible tester will flash a light a certain number of times to indicate a problem with the component.
Replacing it is a 10 minute job, if you don't mind a bit of spillage, you don't need to drain the coolant, you just need to top it up and bleed afterwards ( and the coolant ! )
The sensor costs around £8 from GSF http://www.andyspares.com

tanov
Posts: 7
Joined: 06 Apr 2004, 15:37

Post by tanov » 29 Apr 2004, 12:58

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by mbunting</i>

If the sensor is faulty, the ECU will know about it, and will be using default values, which are good in some conditions, and bad in others, they're there to help you start and run the car.
There will be no indication on the dashboard of a fault, however, a cheap compatible tester will flash a light a certain number of times to indicate a problem with the component.
Replacing it is a 10 minute job, if you don't mind a bit of spillage, you don't need to drain the coolant, you just need to top it up and bleed afterwards ( and the coolant ! )
The sensor costs around £8 from GSF http://www.andyspares.com
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Thanks for your advise.The sensor is realy cheap but how can
I test it before replacement.Is it a kind of a diode?
I think I can measure it when the car is cold and then
measure it when the car is warm.If there is a fault the Ohms
may be the same? (when the fault is full :-)Or may be the values
will be different but not exact?
And I thing that this fault is visible for the Citroen tester
at the Citroen service? I have replaced the throttle potentiometer
there.May be they would catch the problem?
Does the fuel pressure regulator cause the similar problems?
Thanks again:-)

User avatar
uhn113x
Posts: 1161
Joined: 06 Jan 2004, 23:06

Post by uhn113x » 30 Apr 2004, 12:55

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Thanks for your advise.The sensor is realy cheap but how can
I test it before replacement.Is it a kind of a diode?
I think I can measure it when the car is cold and then
measure it when the car is warm.If there is a fault the Ohms
may be the same? (when the fault is full :-)Or may be the values
will be different but not exact?
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Tanov
It is not a diode but an NTC (negative temperature coefficient) thermistor.
You could measure the resistance at different temperatures, but unless you knew what the values should be, this would be no help.

mbunting
Posts: 712
Joined: 21 Dec 2001, 16:19

Post by mbunting » 30 Apr 2004, 21:12

For the sake of a few pounds, I'd just swap it.
It's resistance changes as the coolant temperature changes, so it provides a variable indication to the computer about the engine temperature.

tanov
Posts: 7
Joined: 06 Apr 2004, 15:37

Post by tanov » 03 May 2004, 16:10

Does the fuel pressure regulator cause a choking from a rich fuel mixture? And can I replace it?
When the car is worm the idle is slow and when is cold the idle is
high.So the coolant sensor catches the temperature difference.
Or maybe some other closed loop corrects the problem?(like lambda sensor)?