Ive been looking for a post dealing with my issue, havent found one yet, and im still looking, but I thought id take a stab at asking about it. Ive got an '01 SLE that is in need of its second replacement Catalytic converter. It melted the factory Cat about 160,000. The replacement was put in about six months ago, along with a new downstream O2 sensor. It lasted about 7,000 miles.

The first warning was an Insufficient catalyst code(can't remember the code#). The other symptoms are poor fuel mileage, and when the problem first started, the "Fuel Used" ammounts from the driver information display went from matching the ammount of fuel needed to fill the tank, to being a gallon(sometimes closer to two) less than what was actually needed.

I had thought i had narrowed it down to either the Fuel Pressuer Regulator being bad or a leaking injector. I just checked the fuel pressure and it was 52 with a prime, about 48 at idle running, it reacted correctly to a crack of the throttle. I pulled the vacuum line for the regulator and covered it with my thumb, pressure increased to about 54. It dropped back down when I reconnected the vacuum line. Shut the car off and it slowly climbed from 48 to 54 and stayed for a few minutes. I came back inside to find a fuel pressure leak down spec and havent run across one yet. Just checked pressure after sitting for 40 minutes and it had dropped to 24 psi. not sure if that is good or not.

I dont have an injector spray tester, so I am going to do a resistance check on them. This is where I am wondering if I am being smart or stupid. I was thinking of removing the fuel rail and the injectors and then connecting the injectors back to the rail and prime the system and check the injectors for leaks.

Question 1: What is the spec for fuel pressure leak-leak down? (how many Psi. over how many minutes)

Question2: Am I an idiot for trying to check for and isolate a leaking injector this way?

Question 3: Is there something I am blatantly overlooking?

Let me know if you need more information.

Thanks,
Tyler

What O2 sensor did you use? If it'* a Bosch, then change it again to something else. Those sensors have problems in these engines. When running rich this is one of the first places I look. I also look for a exhaust leak between the heads and the O2 sensor, thsi will show up lean and cause the engine to run rich. You rfuel pressure sounds fine. A leaking injectors would cause problems at start up.

Startup issues, oops I forgot that. It has on 3 seperate occasions not started up right away. I thought it was lack of fuel pressure so I cycled the fuel pump 5-6 times to try to prime the fuel system, and it didnt help. What I did was crank the engine, and play with the throttle like it was a 1971 Bonneville instead of a 2001. Like I said, this has only happened three times, and each time there was no issue once the engine started. I even shut it off and started it, it took right off. Could this be a dirty MAF? Some of the reading I have done has suggested a MAF issue causing some similar issues.

When the problem originated, I had access to a Snap-On Modis. I used it to check fuel trims, and I cant remember the exact numbers, but it had a high negative long term fuel trim like it was trying to correct the rich condition. I no longer have access to anything more than a code reader, so I cant drive it and record data under different conditions.

Oh, and yes, it is a Bosch O2. What do you recommend instead of Bosch?
Thanks

Anything but Bosch.
If you suspect teh MAF you can unplug it and run without it. Just don't get on it real hard. If the problem clears up, then check over the MAF. Tap on it, if the engine stumbles it'* bad.

I might not sound very helping at this sec, j/saw ur post and though to check in, as its very interesting to read, and all the suggestions as well. I cant think of anything right now, but sure sound like Dan is guiding you into right direction. Also, on some new cars, i believe starting in mid 90s they put a fuel shut of mode everyone people pump gas to start, its a safety issue, so if urs equip w/this then it wont give you nothing. infact it shuts off fuel when u full throttle the engine trying to start it that way.

i meant to say every time people try to pump gas

Flooring the gas when starting shuts off the injectors. This is a clear flood condition.

yep, thats what i was trying to say. lol. and Dan, not to get off subject here, but i noticed that the car will start any time as long as u dont run to long, however after a trip it wont start, do i have some kinda condensation prob?

Sounds like a heat related problem. Try putting a ice cub on the MAF when the engine is hot and wont start. If it starts up then you have a bad MAF

When your first catalytic went bad, you replaced the downstream O2, are you positive on this? The downstream merely monitors how well the cat is working. The upstream is the one that can go bad and run the car super rich. This appears to fit into your symptoms of the car being rich, having starting troubles (fouled plugs) and killing the new catalytic in record time.

Being an 01, you won't have good luck using a cheap cat replacement. You'll want the golerich or however it'* pronounced to keep from having an inefficient cat code pop up. I'd swap the front O2 sensor with a new Denso and watch it on the scanner (if available). The other issues you mention about leakdown are quite normal and the issue is usually the checkvalve that is built into the fuel pump. This does not typically cause a problem.

My thoughts are ... changed wrong O2 sensor, plugs are fouled and not firing well cold, and the cat is bad again.