Cold running issues

[Forrest]

Car is a 1994 Wentworth Auto estate with 275k on the clock. There are quite a few small things wrong with it but it has always run quite well. The ones potentially relevant to this fault are:

Speedo doesn’t work until about 20 minutes into a journey, then works faultlessly
PCV system is well overdue for cleaning
Ditto throttle body
Slow coolant leak somewhere, possibly the radiator, possibly the heater valve
Exhaust is starting to blow immediately after the cat
Hole in the turbo air intake hose

The problem is that it has started running incredibly badly following a cold start but then runs absolutely fine when warmed up except it will sometimes stall when braking hard, especially uphill. In these circumstances the dash lights come on before the engine cuts out and I have recovered from the stall on occasions by coming off the brakes.

The first sign of trouble was that it wouldn’t go above 15 mph up a nearby hill from a cold start when someone else was driving it. It has since got worse.

It starts fine, but smells like it’s running very rich. It idles quite low compared to normal for a cold start but revs grudgingly in park or neutral. As soon as drive or reverse is engaged it won’t rev and won’t really move at all. You can put you foot flat to the floor and it won’t move or go above 1,000 rpm. The engine continues running though.

If I disconnect the MAF it runs (even) worse.

I changed the timing belt a few months ago but this problem didn’t start immediately after doing so and it runs very sweetly when warm, so I don’t think it can be a tooth out. I did struggle with the timing marks. The car has previously had the head skimmed.

I have been running it knowing that the in-tank lift pump was faulty for too long; in fact probably about 100k miles and ten years. During this time I have fitted a new main fuel pump.

Based on this 2006 article, when these symptoms started I replaced the in-tank pump just after Christmas.

https://www.volvoforums.org.uk/showthread.php?t=14447

Doing so appears to have made no difference to this fault but the new lift pump does appear to be working and has placated the noisy main pump.

I know as I write this it sounds as though I have seriously neglected and abused the poor thing. In my defence, I have owned it since 1999 and managed to keep it on the road all that time and I keep up with most of the basic service items. It is the grottiest of four cars I currently own and I mainly use it for winter driving.

I’m minded that the air leak is the most likely culprit. I have tried a temporary repair with duck tape (which I don’t think has made much if any difference) and I have a new part on order. I have also tried removing fuse 1 to reset the ECU based on a theory, possibly spurious, that it has got used to running on restricted fuel. I shall know if I try to start it tomorrow if this has helped.

Any other suggestions of what to check or test?