UK Car Repair: my cars hunting on tick over, pipercams, air leaks

Question
i have a clio mk1 1993 its had pipercams and pulleys been chipped and remapped, but it hunts on tick over it will run lumpy because of the cams but then revs up abit then goes back to running lumpy ive checked for air leaks on the pipes there all good and cleaned the idle control valve you can hear the valve opening and closing inside any ideas? and it stalls when you put the clutch down but if you rag it it ticks over high on tick over intill you switch it off and back on again then its back to hunting again any ideas on these one or are they all linked together? thanks

Answer
Water temp sender - it's usually on top of the waterpump or very nearby high up in the cooling system - this hunting is usually a symptom of that sensor either being broken OR because the water level is too low and the sensor isn't touching the water or there's an airlock.

Just to show how this works -

Water level too low: Cold temp reported to ECU
ECU then increases the mixture: Revs go up
The high revs manage to pump some water to the sensor: Warm condition reported to ECU
ECU reduces mixture: Revs go down - maybe stall
Water no longer reaches ECU: Cold condition reported again: Revs go up

Repeat.


Check the water level, if its ok replace the sender.