Has anybody found an answer to the Punto Mk 2 1.2 8valve 2000 Erratic idle ? I have renewed - the complete throttle body , & the MAP sensor & the lambda sensor as well as new plugs, none of which made any difference at all -- just made me poorer, the car seems to be worse when it is hot, this is when the revs fluctuate from 500 to 2000 ish, cannot find any air leaks, it does not misfire, there is no arcing from the plug leads -- help please !!!!!

Hi
I have the same problem with my 2002 1.2 8v. On Mine the revs resonate up and down about every 3 seconds, I sound like a boy racer at the lights. It started with the thermostat sticking closed and the engine overheating big time. I have replaced the head gasket, fitted a different throttle body, temp/air sensor and had the ecu read (the ecu thinks that there is nothing wrong ie: no fault codes) at the moment I am thinking faulty crank sensor (clutching at straws) or resetting the ecu by disconnecting the battery for 30 mins. the only trouble is I dont think I have the radio code or a red key or card with a number on it. I will let you know if I find the solution.
Rgds Robboo.

throttle position sensor range may need to be relearnt by ecu (not sure if 8v need this to be done using examiner or not). this does not show up as a fault during diagnostic.

failing that you need to replace the inlet air temp sensor and clean the idle speed control valve actuator.

failing that its the rpm sensor.

does engine temp have any effect (only does it when warm?)

Hi
I tried disconnecting the battery for 30 mins then reconnected it, started the engine (hoping to teach the ecu a new range) however the engine revs are still up and down weather the engine is hot or cold. I have tried a different idle control valve and temp sensors so i guess the next thing to try is another rpm sensor. Is the rpm sensor also known as the crank sensor?
If this doesnt work I will have to see if the clever lot where I get my cars MOT'D have an examiner.
Thanks

Just for the record, I have found out what the problem was. The plastic inlet manifold had melted at the bottom. This did not show up in a spray test also previosly me and two mechanics could not hear a suction sound.
The way to check it is, put the palm of your hand over the front small crescent shaped hole at the front of the throttle body, If the revs drop to the correct level the engine is taking air from someware else.
Also if you push the manifold down the engine idles okay. If you pull it up the resonating idling gets worse.
All this hastle was due to bad design of the cooling thermostat. It should fail in the open state not closed!

strange fault, never heard of that happening before.

This is a common problem on engines that have had a head gasket failed and seriously overheated. Most dealers have experience of this.

Thanks for all the suggestions, I changed the throttle body, air temp sensor, lambada sensor, plugs, coils, plug leads all of which made no difference & then a cheap new ecu came up on ebay , bought it fitted it & car now runs perfect (cept 4 slight misfire wen warm & under load) but it idles beautifully & rock steady at 800 rpm