renault 1.9 dci missfire

[Road Hog]

my megane sport tourer has an intermitant missfire sometimes going for days with no probs and other times every few miles ,tried changing where i fill with fuel ,made no differance.

any ideas

[CheekyMonkeyla]

Im not sure if they have an ignition coil but i had some misfiring in my 5 series a few months back, could be that...

or also check the spark plugs too..

[Mikey G]

DCi is a diesel, so no ignition system to missfire.

I would say its either a blocked fuel filter or a dodgy injector.

[Road Hog]

had it on computer not showing any fault codes.

??airflow meter ?

[Mikey G]

Road Hog said:

had it on computer not showing any fault codes.

??airflow meter ?

Possibly, is it a full misfire as in it sounds like it drops a cylinder or does it just give a little hiccup and carry on as normal?

[Road Hog]

usually on light throttle it just seems to miss then pickup, sudden fuel starvation or as if it has water in fuel.

[loose cannon]

sounds like a injector issue if there are no faults you probably need to carry out a leak off check on each injector that would be my next step

[orange n blue]

Just had the same problem on a Laguna dci. the engine has a slight hesitation at between 1600 - 2000 rpm.
There is a lot of information regarding this problem on the Renault owners forum and also Parkers forum.
They suggested first to clean the EGR valve. Sticky carbon deposits build up in the valve and prevent it from closing properly.
another thing to check is for leaks on the intercooler or pipework. Ours was a broken housing on the damper valve where the intercooler connects to the inlet manifold.
Last thing, unplug the MAFF sensor and see if the problem disappears. If it does the sensor needs cleaning.
Hope this helps.

[Road Hog]

just one thing what is an MAFF ?

[orange n blue]

MAFF mass airflow meter

[Road Hog]

not missfired since replacing airfilter with a K+N one.
(holding large piece od wood) car goes so much better with new filter .

also found damp round the connector for airflow meter wd40 same.