I was experiencing random issues on my 1992 Super Custom fitted with a 2L-TE engine.
Engine would not rev over 1800 revs, then would kick back in......and drop out again....
I was having to start the engine and leave it to warm up before even attempting to drive away......
Management light giving random codes......then stopped coming on at all...would flash briefly as you cranked
Cutting out whilst driving......
Kicking out diesel smoke all of a sudden....
After lots of attempts over many months to find the fault such as;
stripping down to the turbo to check for operation.
checking throttle position sensor
checking coolant temp sender
trying to flash read the diagnostic OBD1 system.
checking all vacuum pipes for leaks
I did so much research on the net to try and find the problem with this and I was that close to scrapping the whole thing and I am an auto electrical mechanic by trade so you can see it must have been annoying trying to trace the problem.
To cut a very long story short it was the Nicolcon capacitors inside the ECU which are the problem. They are the brown ones and they are only good for about 10 years before they leak acid over your motherboard. I'm amazed that mine lasted 23 years before giving up the ghost! There are about 8-10 various ones with various values depending on your vehicle. Find your ECU and get a magnifying glass to see the acid leak/green corrosion on the motherboard.
Hope this helps
PS To add a bit more to the above fix, since changing the capacitors the improvements I have noticed over the last 3 winter months have been: smooth start up and tick over, faster acceleration and pick up, no management light issues at all, it comes on, you start engine, it goes off, no more random flashing or on the road dramas!, and the one I love is that amazingly the air conditioning which suddenly packed up in 2007 has began to work again after 9 years dormant!
There is a lot of info on these Nippon Denso ECU capacitor issues on the American Lexus Owners Web Site which was a gold mine of info for me, one of the guys discussing worked for Nippon Denso. I certainly do not regret biting the bullet getting the soldering iron out and diving in! It is like a new vehicle!
I road tested it a few days later by driving 100 miles (with breakdown cover in place!) Birmingham to Peterborough and back again, so 200 mile round trip and no problems. in fact it was so fast it felt fantastic.
PPS The Nippon Denso ECU's with the volatile capacitors I mentioned were widely fitted to many different makes and models from around 1989-2002. My 2.4LT-TE turbo diesel engine has done 224,000 km.