My Megane is having the following problem when starting. When I start the engine and try to pull away I get no response from pressing the accelerator. The engine revs are slightly lower (about 850rpm looking at rev counter) than normal idle speed and the car sounds as if it’s very slightly firing on 3 cylinders. After a period of time (Normally 10-20 secs but once or twice as long as a min) the revs will increase and I get accelerator response. I'm guessing that the ECU is not letting the car rev due to the low idle speed.

This fault never happens when the engine is started from cold, once running, the engine runs fine with no problems. It seems it’s linked to a hot engine as I can drive the car with no problems, stop the engine to say fill up with petrol or post a letter and when I go to restart I get the fault.

Sometimes if I turn the engine off and restart the car will behave normally even thou the engine is hot. Turn it off again and restart and I get the problem.

I get no warning lights on the dash and as said previously there is no obvious issues when driving.

I've checked the wiring and carried out a "wiggle" test of all the connections and can't replicate the fault. I have also tried to observe the engine whilst it’s having the fault but as it generally clears within 10 - 20 secs fault diagnosis is difficult due to the short time.

Someone has suggested it's an injector on the way out so I am planning on carry out a leak off test to see if this can shed a light on the issue.

In the meantime any ideas? Has anyone come across this before?