I've been chasing my tail with this issue for a while, I'm posting it here, where there are a lot more Toyota engined cars, in the hope that someone has seen this problem before.
I've a 2004 Elise 111R I've owned for three years. It has a 2bular exhaust and TRD induction. It has recently been suffering an intermittent loss of power at high revs. Sometimes it is fine, sometimes it isn't. This is with the engine properly warm, obviously.
I have just had the ECU reflashed to lower the cam change point. Since refitting the ECU, the problem has been continuous - the cam change happens (at 5700rpm in my car), the engine note changes, the car continues to accelerate briefly, but then bogs down and goes completely flat from 6000rpm to a little over 7000. It then picks up a bit and starts to accelerate up to the shift light. I was pretty confident that this was the result of the pre-existing problem and not caused by the reflash, but it was hard to be sure.
I had it in to my Lotus specialist yesterday. On the way, it threw a CEL while sitting in traffic. The diagnostics said misfire, but after clearing the code it didn't do it again. They have changed the plugs, looked at the cat, checked the fuses, checked over the sensors, problem persists.
I took it out today, warmed it through and - problem gone. Bit of hesitation the first time I took it over 6000rpm, but then perfect after that. Drove it for about 7 miles, all working properly, lowered cam change and all. Parked up. Came back ten minutes later. Problem is back. At least I know for sure it isn't the reflash, it's definitely the same issue it had before.
This is what it looks like:
I don't think it's a problem with the VVTLi mechanism - it sounds as if it engages and it revs right through to over 8000rpm.
I'm wondering about coils. They've been out, cleaned, greased. They're an expensive thing to try replacing as a diagnostic exercise, though.
Anyone seen this before?