Missing just above idle

[coolrunnings]

My 2.1 litre DJ engine has a flat spot just above idle, causing engine Rev drop out. I thought it might be LPG controller but does on petrol too. When van is stationary and I slowly increase revs, just above idle the revs drop out until pedal pushed a bit further and the engine recovers. When driving this causes the van to lurch when operating around this region.
Thoughts on where to start....plugs, leads are all relatively new...

[Aidan]

I'd be looking at the idle control system as often when something in that isn't working bits get bypassed and idle screw and co screw get messed with to make it work and take a look at the output from the airflow meter as if that signal drops out then ecu doesn't know what is happening

[coolrunnings]

How do I check airflow meter output?

[coolrunnings]

And the idle control system....what and how do I check?

[Aidan]

download the DJ manual from syncrosport website the procedures for checking it all is in there

[coolrunnings]

Ok...checked resistance output from AFM and all looks ok, the point in the acceleration curve just above idle is so slight it really looked like a dirty spot on the AFM wiper, so I took the unit apart, popped the lid off and cleaned the track with isopropyl alcohol. Put all back together and it's currently working ok.
However the idle stabilisation valve is not vibrating or buzzing with ignition on or engine running. The resistance is in the range specified at 4 ohms and the continuity to the relay by the right rear tail light is good.
What's the recommendation, new idle stabilisation valve or relay?

[Aidan]

try cleaning the air bypass valve by soaking the working end with brake cleaner or carb cleaner as they often become gummed up and then stick in one position and the rest of the air intake/bypass gets opened up to allow it to idle, tends to rev a bit at idle when warm when that has happened, but the white plastic control unit is often suspect as are the contacts of the idle control unit behind the right lights so pop the light out and remove the idle control unit and clean contacts and relay holder with contact cleaner
and the idle controllers do fail usually a blown capacitor if you search on here you should find details of that repair

[syncroandy]

^WHS re. contacts. I just had an issue with my TDI (1998 harness) it was surprising how much brown cack came off the G80 sender contacts using some Wurth cleaner and a cotton bud. On an older engine like the T3, contacts can get severely corroded. I worked on a DJ harness recently and had to replace ~20 contacts due to corrosion.

[coolrunnings]

Aidan, thanks for all the useful advice. As it stands I appear not to have a functioning idle control system...but I don't have any symptoms that would be associated, high idle for example. I will try some of your fixes at the weekend.
Cannot find a decent explanation anywhere as to what the system does, can anyone point me in the right direction.
If I don't have any current issues, should I just leave well alone?