The car is a 75 SX. For the last couple of months it has been starting fine but with a misfire for the first few seconds. Thereafter it runs fine until the engine is properly hot. It will then snatch and stutter under light load at small throttle openings, particularly if coming off the overrun, but runs fine at higher speeds. This makes it a bit annoying to drive around town.
The plugs and plug leads are fine. I changed the Lambda sensor since this seemed the most likely culprit but the problem persists.
What next? The coolant temperature sensor? The car idles normally when warm so I'm inclined to think this might be OK.
The air temperature sensor? How do I check it? Anyone got any resistance figures at 20 degrees C ? Absolute pressure sensor?
Then there is the charcoal box thing and it's valve. What is result of the valve not functioning?
Is there anything else?
Oh yes, and the engine management light comes on intermittently. So presumably something is outside it's normal parameters.

hey i had the same problem on my punto mk2, you may want to try the injector wiring, it is fairley cheap to put right. is there an engine warning light up??? if so it is probably the injector wiring

i hope this helped

if the light is coming on, take it to a place that can read the ECU data - see what error its picking up. Could be the MAP sensor. Misfire in the first few seconds is also linked to coolant being in the cylinders.. is it loosing any coolant?

Punto 75 are prone for the coolant sensors. The sensor plugs become green and give incorrect readings. the sensor lives in the theromstat housing. These also cause revving problems ect. If you going to replace it make sure its a black one thats in it and make sure you fit a black one not a blue one as this has got different resistance values.

Thanks for the info guys. Now injector wiring is a possiblity. The problem started almost immediately after I did a service and of course I had the airbox off to get at the plugs which are right beside the injectors. Perhaps the wiring has got disturbed. I'll make sure that all the connectors are firmly in place.
Coolant sensor is also a possibility, I was hoping some one might have the specifications for one. i.e. Resistance at a known temperature like 20C.
I'm not keen to take it to a dealer to get the error codes read if I can help it. Dealer = money!