Weird D1 stalling problem

Okay, I'm nearly at the end of my rope with this and am hoping someone will have a brainwave about it.

The background: I have a '97 D1 that was originally auto (ZF). Last year I converted it to manual (R380) and in general it runs perfectly. But there's one issue, in that under certain conditions (below) the engine just flat out dies.

Starting, shifting, and driving are all fine. But if you downshift (especially if doing so really revs the RPM) then push the clutch in, about 10% of the time the RPMs drop immediately to zero and dies. I've also noted it will go into this mode if you've been just using engine braking on a gentle downhill run (no downshift, just basically coasting). Popping the clutch generally restarts, otherwise it kicks right over with the turn of a key. On the road it gets 16-18MPG and the engine is absolutely smooth.

What's been done so far: IAC, MAF, and TPS swap (I have good spares for all 3). New fuel pressure regulator. Plenum chamber removed, resealed, and cleaned. All vacuum lines renewed and checked. Plugs/wires new last year (3k miles, no more). Air filter also new, etc. Working on replacing the fuel filter (age unknown, probably original) on the off chance it's involved, but one fitting is seized and I haven't gotten enough PB into the fitting to loosen it yet.

The shop that did the swap is very good, and they're scratching their heads. I've talked with a few other folks and no one seems to have a handle on this, so I'm looking for weird things that might have been missed. I'm pretty sure the shop put the proper spacer on the crank sensor, and the ECU is from a manual car thanks to another LRO who sent one my way a few weeks ago.

So...ideas, please before I give it to someone as target practice?

Thx,

dj

How do you set the min idle and so forth on a D1? This is all handled by the ECU AFAIK.

On the ECU, it's from a manual car and it's been exhibiting this problem from the time it was installed (I reset adaptations then). I've put 400+ miles on the car and there's no real change. Behavior was exactly the same as with an auto 'box ECU, in fact.

Some of the behavior is just weird. It'll sometimes (not always) stall even if you haven't downshifted, but have been using engine braking on a long gentle slope. Sometimes yes, sometimes no. There are absolutely no errors in the OBD system either.

It almost feels like it's starving itself of fuel. I half wonder if it's something as easy as a clogged fuel filter, but I'd expect that to cause problems during hard acceleration/high demand.

According to the guy who sold me the ECU, it came out of an AEL vehicle. The car is AEL (rectangular carbon canister) so I'm hoping that's correct. I've never been able to find a list showing which part number matches a particular set of characteristics.

That said, the original ECU in the car was AEL and exhibited the same symptoms.

Yep, it's a stumper.

I'm pretty sure the VSS is okay, since I have a ScanGauge hooked up and it reads consistently. I've finally sourced a new crank sensor (note to all, these are becoming unobtainium from even after-market sources and Rover has none left they'll admit to) and will be swapping it out shortly. Fingers crossed.