90 Pontiac 6000 LE Problem

Had a similar problem. Car would start fine then steadily idle rougher after it warmed up. Once it was put in gear, it would die out. Come to find out, it was the catalytic converter. The older ones use to come apart and restrict the airflow out. Some of them had a big plug/patch on it that could be popped/pried out. Depends on the type of converter, some had pellets/beads and some honeycomb. Sometimes you can get under the car and tap or hit the converter and hear stuff rattle inside. If that is the case, "legally" it should be replaced but will run fine without the guts in the converter or no converter at all. Hope this helps.

If it has a carb. then it should have a mechanical fuel pump on the front left of the engine (as you look toward the back of the car). Once you find the pump, crack open the line from the fuel pump to carb, (while holding the back nut). Have someone crank the engine with the line cracked. Should get fuel out of the open line. If not, open a little further and try again. If still no fuel, tighten line and find the fuel filter. It might be clogged. Change filter. Some motors have two filters. One in-line between the gas tank and fuel pump, and then one at the base of the carb where the fuel line from the pump connects. This is more of a strainer, but they do get plugged. They are usually half as long as your pinky.

Is this fuel injected and if so, is it Multi Port (MPFI) or Throttle Body Injection (TBI)? If it is MPFI, crank the engine a couple of times and go to the fuel rail. There should be a air cap towards the back. Remove the cap and take a long skinny screwdriver or awl and carefully depress the valve stem. If the pump if pumping, there will be fuel pressure there. Not sure how much depends on the engine, pump etc., some 9 -13 psi and some 25 - 44 psi. Need to know what type engine. I can't remember what size mine was but I think it was a 2.8L. If it is a TBI, you should remove the air cleaner and look down in the throat and see the injector(s). When the engine is cranked, you should see fuel spraying. The fuel pump for the fuel injected engines are electric and in the fuel tank and 99% of the time the fuel tank has to be dropped from the vehicle.They can be a pain, especially if the spanner nut is rusted in place. Best suggestion is get a can of PB Blaster and soak down the nut before attempting to remove.

Thanks for the advice. I will check the fuel filter and will try to check the catalytic converter tomorrow. I don't know if I'll me able to get under the car far enough to get to it though, but I'll try. The car is multiport fuel injected, 3.1L V6. One thing I failed to mention is that when I'm trying to start the car, there is a strange humming noise coming from the back near the gas tank.