Engine Idle Not Very Good

Hello
I wonder if anyone can help me on this. My 3.5 efi will not idle when it is hot. It is ok at start up but once it reaches working temp it starts to idle erratically ie tacho swings from nearly zero to 500rpm. Any ideas?
Regards and a Happy New Year.
Mik

idle air control valve blocked

I would try another engine Ecu if you can borrow a known good one,hunting at and just above idle are exactly how most Lucas 4cu Ecu's die.3.5 RR's had a simple electric and manifold heated bi-metallic strip idle control that slowly closes as the engine gets up to temp.A/C equipped models should have an extra fixed orifice valve that opens when the A/C clutch engages.(when dealers retro fitted A/C they didnt always fit the valve,ok when the engine is new - when they get tired they stall when the clutch engages)

could you please tell me if you solved the idle problem with your 3.5 efi as i have the same problem ,will not idle when at running temp.

Hi
Yes I did. I bought a used ECU and that seemed to cure the idle problem but I had a bit of rough running mid range. I fitted some new plug leads and dis cap and it's been running really nicely. Hope this helps you and I really should have posted the results earllier.
Regards
Mik

thanks for the reply mik,a great help, now just have to find a good used ecu or maybe have my one looked at , i will post the results, thanks again uncle munkle.......

Check the rotor arm. They are prone to breaking down to earth especially the aftermarket ones. A 3.5 Disco I had was in the garage for a week and they couldn't sort it. Pulled it out and tried all the checks and found that the main H.T. lead from the coil when held away from the rotor arm was tracking across like Blackpool illuminations when the engine was turned over. New OEM (Lucas) rotor and the problem was fixed. So much for the "Experts" who think owners have a bottomless wallet and no brains.