saxo cuts out when at lights when cold

[yellowperyl]

When my Saxo 1.4 furio is cold it tends to cut out at lights, junctions etc, but when it is warm it runs fine, any ideas what could be causing this problem, I tried a new stepper motor but the problem is still there, any ideas?

[AndersDK]

Also experiencing a bit of starting problems on chilly mornings ?
How about engine fault lamp ?

[yellowperyl]

no non of those, but it starts to rev upto around 2000 to 2500 revs on its own without me touching the throttle before cutting out.

[johninderbyshire]

my xsara 1.4 keeps doing that, and after 6 months of doing it, my stop light wont go out and the temperature gage goes up very quickly. My local garage has said he thinks it is the head gasket....... we will see!!!!

[AndersDK]

Ahhh...

A blown headgasket will never ever cause mysterious settings of the rpm.
But "ghosting" revs is a common sign of the throttle pot worn out.

[yellowperyl]

is a throttle pot another name for the throttle body? if so surely mine can't be worn out at 53,500 miles can it? was thinking, is it possible that the coolent temperature sensor is faulty?

[AndersDK]

good point there - they shouldnt wear until some 150K+.

But its not the throttle body - its the side mounted throttle flap position sensing potientiometer (sorry !). If it it wears a "hole" in the carbon track it will cause the engine revs to hunt when at the hole position.
You got a brand NEW body fitted surely ?

The coolant temp sensor (CTS) may cause intermittent settings of higher revs - if there is an intermittent connection in this sensor or its cabling.
If this sensor (or cabling) disrupts - the ECU is signalled a high resistance which is similar to a cold sensor - and the ECU will "choke" the engine - no matter what temp the engine is at factually.
This also means that if you disrupt the sensor at hot engine - the engine shold immediately start run worse as it suddenly gets too rich a mixture.
This will indicate a good senor and cabling.

On the other hand - on hot engine if it does not changes on a bad running engine disrupting the sensor - then try instead short out the 2 pins in the sensor plug (cable end). This will signal a hot engine to the ECU - and it should immediately start run good and clean again - positively indicating a disrupted (defective) sensor.

The scenario is somewhat "painted over" by the Lambda sensor which will try correct any richness caused by a faulty CTS sensor.

Least but not last - there is an air mass (MAP) sensor somewhere in the throttle body. On later models its located at bottom of throttle housing. They can make a mess if they are gunked up by oil and dirt from the intake. They do fail from one day to another for no appearent reason.

Bet you already have tried your luck on all connectors and cables round the throttle body and engine cylinder head ?

[yellowperyl]

Whilst waiting for my engine to warm up to try shorting out the coolant temp sensor, it began to speed up and sounded like it was going to cut out yet again, so I removed the wire from the green temp sensor and the engine began to run smoothly without shorting it out, but when I put the wire back on again it went rough again. I have since been driving my car without the green temp sensor connected and everything has been working fine, does this sensor need replacing or will it be fine just leaving it disconnected?

[LeicsVTR]

Anders - You have just saved me a possible few hundred pounds. Unplugged my temp sensor lead it's running a dream! This problem's been going on for months.

I can't stress how grateful I am. If you're ever around I'll buy you a pint!