Hi I have a Rover V8 3.5 in my series 3 the engines done 6000 miles since I fully rebuilt it, the engine was originally from a Rover P6. It's ran fine for the last few years but over the last few months it has developed a problem with randomly loosing power. Some times it feels like a misfire, just a sudden hiccup then returns to normal straight away. But other times it can loose power for about 10 to 15 seconds at a time some times more severely than others. Some times you can just hear the engine struggling a bit but doesn't slow down very much but other times it has very quickly slowed almost to a stand still whilst going down hill as well, at the time I though the throttle cable must have snapped but just as quickly everything returned to normal and I suddenly shot off down the road. I've noticed that when this happens the rev counter stays steady so I think that the electronic ignition is working OK, I have noticed though that the coil gets very hot, it always has done and this ones been on about a year the old one was the same I only changed it so I had a spare. How hot should the coil normally get? The HT leads are new Magnecore ones so I think there OK. Distributor and rotor arm are OK. The spark plugs are a bit old now so I'm going to change them today anyway. I have a vacuum gauge connected to one of the SU carburettors, when the problem occurs the gauge shows very low vacuum, What would cause the low vacuum level? I've stripped both carbs down and replaced seals valves etc and carefully set them up but has made no difference to the problem. My other thoughts are the fuel pump and filters, I think I may change the filters today but they look OK (clean inside) they are the see-through plastic inline sort of filters. As far as I can tell the electric pump is working fine and the problem can occur with a full or nearly empty tank so I think the pick up pipe is OK but I'm going to check that today. The problem can occur in all weather, it can keep doing it all day one day then run fine for the next few weeks or so. Anyone had problems like this before? Any ideas on this problem gratefully received.
Thanks Liam