My sony 800 w amp dies after a few min. One time it only went on when i gassed the engine

Sounds like you got some bad gas. May need to replace the fuel filter

You obviously have to replace a worn out
& melted or broken cat, before you can diagnose
anything

If the cat is bad you got no fuel control,so the cat goes,
as well as the oxygen sensor

Odds are the timing chain gears are worn & it jumped time

You may have vacuum leaks

1990 doesn't have a carb it has a throttle body !

So you check test the tps sensor & it's adjustment,if any

You test the cts,ats,& map sensors

Air --In---Air--Out---not with a blocked cat,thus most
of your problem,maybe a clogged gas filter as well

The fuel pressure sounds too low. Is it multi-port injection? Check the fuel pressure against your specs for the car and engine. MPFI systems usually require 40-50 psi.

if the wiring to the sub is correct, then you have something wrong with the amp itself... something is power surging to the subs which is causing them to blow

did you replace all diaphrams in carbs and fuel pump ? balanced the carbs ?

passably the cover on you motor should stop water from getting in or you got old fuel, or bought bad fuel if possible water in fuel tank buy a bottle of heat this will remove water from fuel tank, replace fuel filter if one or drain moisture trap on engine fuel system.

Monitor has gone to monitor heaven. time to do some shopping since repair not cost effective.

check your engine colant temp sensor. it will tell your computer that its -66 and send loads of extra gass wich will flood it. couldnt explain the smoke tho

try to check the throtle body if it is tight ok...

Sorry, Sony is having a lot of problems with the light engine ($$$) on these models. Contact Sony as they are covering them even though they are out of warranty (class action lawsuits)