740 running rough on holiday

OK! Need help this weekend ie: 19th 20th june
Drove down to exeter from Birmingham (with family incl. three children under age of two years)....2ltr pertrol injection automatic started runnung rough for last twenty miles on friday night.Mainly on idle but seems to be struggling a bit even when it is changing up gear, it cuts out at times on idle.
Next morning ie Sat and called out recovery service who say its somthing with the injection system...engine runs better on idle when air meter attached to air filter is removed...has no idea why!
Phoned arround recmmende garages from volvo site ...no awnser.

So any ideas you guys.... Can I leave this sensor disconnected to get home or is there any thing else I can do or can you reccommend a close by garage who will be able to diagnose my problem......if so please call me on 07813-103944 today sat or tomorrow sunday 20th June...I will phone you back. Thank you Patrick

[Peter Milnes]

I assume that you have thoroughly cleaned the inlet tract (air filter, Idle Air Control Valve, Air Mass Meter, throttle block and checked setting of throttle microswitch) and checked the wiring looms in engine bay and the ICU & ECU wiring and also the ignition power amplifier and crankshaft sensors. It is not uncommon for the "radio suppression" relay to fail if your car has LH 2.4 fuel system. It provides an earth return for the injectors. Let us know what has been done/not done and which fuel system your car has. It could be any one of four.

All the best, Peter.