Hard or no start intermittent issues
 

2003 98,000 miles on the ticker.
Started with a slight miss. Then barely running missing and surging with varied gas peddle pressure (power and acceleration coming and going).
changed out the spark plugs. Hard to start then ran ok. Unplugged the MAF sensor and it smoothed out. Changed the MAF sensor and it ran OK for a short while. Tried to start it hot and it was a no go. I let it cool down and it started but ran terrible then idle smoothed out after reving the engine a bit. Has a bunch of codes in it. O2 sensor, low temp coolant sensor, catalytic inefficiency issue are I believe all the codes it spit out. Exhaust sounds kinda weird making me think I might have a plugged cat. It doesn’t smell bad or of anything with a somewhat Frey color if any color to it. This thing has gremlins or something as it runs fairly well sometimes. When it does start we’ll and runs well it would never start on the first crank, always the second.
Any helpful hints or ideas?

What were the codes you obtained ?

There could be a problem in the vehicle , but we can also do a forced reset. That consists of removing the negative battery from the battery and holding the end of the negative cable against the battery positive cable for a few minutes. This allow the learned memory to go away and any gremlins with it. The problem that also is now present is you will need to reset all radio stations, memory seat, mirrors etc. After you reconnect the negative back on to the battery, start the engine , BUT do not touch the throttle pedal. Allow the engine to relearn the idle speed settings programmed into the powertrain computer. This can take a few minutes, 10-15 minutes. Then drive the vehicle normally to relearn your driving habits (shift scheduling). Let us know how you make out with this, thanks.

Somewhere on the horizon may be a possible fuel pump problem.

I don’t remember the codes exactly and cleared them as I had unplugged the MAF sensor so I was going to run it some more to see if they come up again. There were two O2 sensor codes, a catalytic converter code and a temp sensor code. I don’t believe there was anything else.
I hate the replace until fixed approach however this is often the case when some shops get ahold of your car too.

It won’t restart after getting hot.

Power and performance comes and goes.

Sometimes it starts,runs and idles OK and sometimes it coughs shudders and takes pumping the accelerator to rev up and clear......if it will start.

Any recommendations as where to start?

I think the cat is plugged. Should I start there?

There are a few different approaches you might take here.
In either case we need to know if we have fuel and spark.
You could spray a little carb and choke cleaner (closest to gasoline) into the intake when it won't start then if it starts that would suggest a fuel supply problem..
You could also rent a fuel pressure gauge , connect it to the fuel rail at the Schrader fitting and when cranking the engine over see just what fuel pressure you have.

If you suspect the converter as being plugged , all you need to do is connect a vacuum gauge to the intake manifold and see what reading you get If you do this when it will start you will notice the vacuum gauge reading go higher and higher as you hold the engine speed constant (high Idle 2000 RPM) meaning it is building up PRESSURE where it should have vacuum, and that would confirm a possible plugged converter. It is much cheaper to do the tests than replace good parts and still have the same problem. Do you want to go this route?
I noticed you stated the problem comes and goes, a plugged converter will not allow it to run good and bad , just bad or not at all.

Classic crank position sensor.

I have something you can try that can confirm if the crank sensor is the culprit when you have a hot no start.

When it is hot and will not fire up, open the hood and spray some cold water on the crank sensor. If it starts now the sensor is the problem . If not. , look elseware.

Hanky, You hit the nail on the head with the first reply. Thanks for all your help and replies!!!
It took me a minute or two but I just tested the fuel pump pressure today. I think the gauge isn't calibrated well and reads a little bit low, but....... 0 psi key on no start. 20 psi running. Time for a new fuel pump. There's still something "jenky" with the exhaust, but the fuel pump is toast for sure.

Old car. Don't want to spend too much money on it if I can help it so a Delphi or AC Delco pump probably won't be the first pump I look at and buy. Any suggestions on something else......no I'm not going to throw in some Chinese junk but I'm not in it for $300+ if I can help it either. Is an Airtex pump worth a shiz? I've heard good things from some about Airtex but about the same amount say steer clear. Suggestions?

Since I don't know the present condition of your vehicle, consider this,

With just the mileage listed, there is a lot of good service life left in your vehicle. They can easily go another 98,000. If you are planning on keeping it that long , put in a OEM pump and duplicate the miles. If you are planning something other than that, an aftermarket pump should cost possibly less and may or may not last as long.

New Delphi Pump
 

New pump. Run it for about 200 miles. While driving up a canyon (pretty steep) the car died. No cough sputter or miss just dies.
It failed to restart immediately and would sputter a bit.
20 minutes later it fires and has run fine since.
Potentially a bad new pump?
Something else?

The fastest way to eliminate the crank sensor is the cold water trick. Next time try it.