Hi Paul
I appear to be having a similar problem and have posted my problem on the forum:
I have just converted my CVH powered Westfield SE from Carburettor to EFI, due to strict German environmental laws. Basically I have taken the complete engine, loom and control system from a donor XR2i car. Everything is now installed into position and the engine is running, however it is running very rich (CO2 = 2.3%) with all sensors connected. When I unplug the lambda sensor the engine runs better (in emergency limp home mode I guess).
Since initial posting I have replaced the Lambda, Coolant Temp & Air Temp Sensor the engine is now running slightly better, my next option is to replace the Throttle Possition Sensor. I'm hopping that this is the route cause for the engine running rich as there arnt any other options.
Basically to answer your question: It should be safe for a short time to unplug your Lamda as the EEC will automatically run the engine a little richer than normal (Basically to prevent the engine from running too lean and melting the valves & pistons etc). With the lambda unplugged your fuel consumption will increase and your emissions will be outside limits. Note: a rich running engine will increase the degredation rate of your Cat, so fit a new Lambda ASAP. They arent so expensive I bought a universal one off EBay for 13 quid.
Last edited by vonwoodster; Apr 19, 2009 at 07:39 PM.