Well Guys n' Gals, standby to be educated (I don't accuse you all of being UNeducated, but you are probably not aware of the following). I am about to bring the saga of the hunting engine to a close. Having spent £thousands on this car still no-one had a clue as to why it was doing it. I got totally fed up with taking the car here, there and just about everywhere, running up bills all the time for no improvement. So, I am a retired High Voltage Electrician (11kv AC). I know a little about DC in vehicles, but am no expert and have not wanted to rummage in amongst the festoons of wire behind the glove box. However, desperation decreed I should try to find out what was going on for myself. The Elanscan was confusing everyone, including me, so I did not pursue that line. Then, whilst spending more money on parts for the braking system, I was talking to Steve of S C Sportscars and mentioned the hunting problem. He didn't know what was causing it either but he said something that got me thinking. He said he had a feeling that sometimes this occurred when the ECM had been chipped. Now I know mine had not been 'chipped' because I have another ECM and, in any case, a new one had been tried with no result. So I poked about, gingerly, amongst the wiring and found a mysterious package wrapped in foam. It had four wires plugged into it. It turned out it was a Piggy-Back ECM! When I unplugged it the engine ran smoothly. Hurrah!!! I thought. I've cracked it. Well, I was a bit previous here because when I drove the car it was OK until much of a load came on the engine, like changing up to third and fourth, or going up hill, when it coughed and spluttered and tried to stall. Gentle use of the throttle and dropping down the box helped a bit and at least got me home. I found the engine light was on all the time and so I produced my trusty paperclip and a code 34 came up. I took the car to the workshop and told them the story. Unfortunately, they misunderstood what I said and fitted a new MAP Sensor. No result. Then a sub-contracting vehicle electrician came on the scene. He phoned me and asked for the full gory tale and when I mentioned the piggyback unit he said the wires would have been cut from the main ECM and diverted to the pbu. He was dead on! He connected the wires back to the main ECM and BINGO, ALL IS WELL! The car now performs as Mother Lotus intended. End of Saga! Armed with this new knowledge you can now sort out any other poor sod who comes on the Forum with a hunting engine.
My sincere thanks to all of you who tried desperately to help me in the beginning. Where I could I followed all your suggestions with no avail. What I cannot understand is how the 'experts' at Lotus and three of their dealers didn't find the b....y piggyback unit (I didn't know there was such a thing myself), when they had the car for weeks on end. So now you know!!!
Mike.
