96 Achieva 2.4l exhibits occasional crank-no start. CEL trouble code P0420, catalyst inefficiency. Runs on ether, usually starts with 1st or 2nd ether shot. Replaced coils and housing, plugs, boots, crank sensor, fuel pump. What else can I try? I’m getting desperate!

I’d try draining the ether out of the gas tank and try gasoline. Take it to a shop and have it diagnosed. By replacing parts you have spent more money than was necessary.

If it will start on ether, the problem is fuel related. Did you replace the fuel filter along with the fuel pump? You should have. Your next step is to check your fuel pressure and compare it to spec. You also need to watch the gauge and make sure the pressure is not bleeding down. Fuel pressure regulators are fairly common items that need to be replaced on these cars. Yours may be bleeding back into the tank and not allowing enough to remain at the injectors to start the engine. Your fuel pump relay is also a possibility, but a distant one if it will start and run consistently with ether.

Forgot to mention, yes, I did replace fuel filter. Had not thought of pressure regulator. Will check that and relay out tomorrow. Thanx, I’ll let you know how that works out.