misfire from k series

[NickB7]

i have a new 1600k that starts fine but for the first 20seconds struggles to run cleanly then it is fine. It only happens from cold and never when the car is warm

[Peter Carmichael]

Is it an EU3 or an older engine? If it is the old model this can usually be fixed by resetting the ECU's control of the "idle air control valve". The procedure is to:

1. Turn off the immobilser

2. Turn on the ignition but not start the car

3. Press the throttle to the floor slowly and fully release 5 times

 

Switch off and when you next restart it will try and learn the appropriate IACV opening for idling.

[Peter Carmichael]

Sorry. Just reread. You are talking about running rather than just idling which changes things.

 

In the very cold this can just be down to getting some heat into the spark plugs so that they don't foul, but on a standard 1.6K this shouldn't be an issue.

 

For cold starting you need to chuck in extra fuel because not as much of the injected fuel vaporises and mixes with the air. A lot of liquid fuel coats the inside surfaces of the port and droplets will get carried onto the spark plugs and can prevent them sparking 100% cleanly. Once they have got the idea the temperatures in the surfaces around the combustion chamber get hot enough to improve the vaporisation. New spark plugs and the correct gap may help.

 

It is a bit surprising on a new engine though, so it may be that the electronics are guessing the wrong amount of fuel. This should be diagnosed by looking at the sensor inputs for the ECU.

[NickB7]

thanks peter - it is a new engine EU3 and does it every time. i will look at the sensor connectors and see if anything looks amiss. it is not even supersport so completely standard lump so it is unusual that it does not run cleanly. There is some popping and banging out of the exhaust - is that because too much fuel?