Tried the above and in my investigations, found something intriguing...

Firstly, cleared error codes and they didn't come back until i unplugged sensors again, so that's all they were indeed.

Readings and status were all stable and as expected.

Disconnected the stepper when it got up to temp, it was still hunting. Disconnected the tps, still hunted. Both times, car idled worse and came close to stalling as it hunted. Every sensor i disconnect seems to make it run worse.

I regapped the spark plugs to make sure they were all at 0.9mm, still popped and hunted, though i felt perhaps the tiniest fraction less often and less severely... interesting.

I then put the whole system under an almost full electrical load at idle, Headlights, hazards, heater fan, demister, rear fog, radio..... hot idle? perfect. very stable, absolutely no popping, Ecu was trying to target 864 rpm the whole time and it was fairly consistent around 859 (the lowest it dipped at all on IES readout) and 875 (the highest it went above target the whole time under load). As soon as the electrics were all off again, the idle pop, dip and hunt combo returned.

So that suggests to me the issue isn't a fundamental mechanical one and is related to electrical load.



Earths are all super clean, so not too sure where to start, but at least i have a direction now to investigate!

A further update (always handy in case anybody else ever has this issue with a 16v conversion).

I "think" the issue is resolved.

I was struggling to trace anything wrong electrically so went on a hunch that the above video with a high electrical load was simply masking the real issue and it had to be something more deep rooted in the mechanical side.

I'd reconditioned the head recently so was pretty much ruling that out so attacked one of the constants, the camshafts. Obviously with them in the cambox it's hard to really inspect them, and i had a set of Stilo cams lying about, so figured it was worth a test. Either it changed nothing and i could swap back or i found it and worst case, i'd lose a bit top end power with the less spicy cams but could always source another set eventually to get it back.

Anyway, finally swapped them over and got it running and all seems fine now on the stilo cams. A quick look at the mk1 cams didn't show anything super obvious at first glance, but on closer inspection a couple of the lobes were unevenly worn.

both a good and bad result i suppose.. does this mean perhaps some aftermarket cams down the line sometime??

Perhaps, i'll see how i get in with the "watered down" cams for now, what i'll have lost at the top end i'll hopefully have gained in a fraction more low down torque, which the 16v lacks anyway. It's far from ideal and a massive but not the end of the world and hopefully only a temporary compromise. 1.4 cams are becoming easier and easier to come across, not sure how far away they are from the mk1 cams but worst case scenario, they'll be a better compromise between the 2 if i get really stuck and unhappy If not, i have the old cams i can maybe get reground or something.

Hopefully i can get it mot'd now and take it from there, just getting it working and motable was the first goal after all this time haha.