Yup I'm in Canada. Always logical, smart on good days, but I probably wouldn't say I'm a self proclaimed freak.

That makes sense I didn't completely understand the open vs closed loop. I'll keep looking for it. I'll be moving home in a week or so and I'll have a couple more gearheads around to help me out so I'm sure I'll get to the bottom of it. Sucks that the cat is taking a beating, hopefully the drive back doesn't make life any worse.

 

As long as the CEL does not flash the cat should survive. When it flashes the catalytic converter is at risk.

 

Then you must be boring!
Change your hair, like mine!
LOL!

 

Okay so I got the rest of the vacuum lines replaced the other day and unsurprisingly I still have my issue. What's nice though is that I was able to get some good data out of a code reader on the freeze frame for the CEL:

load pct - 15.3 %
Shrtft1 - 14.0 %
Longft1 - 14.8 %
RPM - 819
Speed - 0 km/hr

Also I was able to get some live data while the car was warmed up and idling. Not sure if the O2 sensor measurements are usable, I've heard you should be around 2500 rpm to get some comparable values? Anyways this was also after the code was cleared:

Shrtft1 - 5.0 %
Longft1 - 14.8%
Sparkadv - 20
IAT - 18
MAF - 2.5
RPM - 700
02b1s1 - .1 & .8 V (flipped between the two)
02b1s2 - .430 V

So obviously the first values are fuel trims which aren't as bad as I thought they'd be. I've heard of some people reaching into the 50's. Not sure why the long term trim isn't affected by the code reset though. Also the last values look like the 02 sensors upstream and downstream of the catalytic converter. The first one might be okay, depending of course on the cycle time which is hard to determine. Is the second supposed to stay constant though? If so it should probably be exactly at .45V though right? Indicating a perfect air mixture. So it is .02V on the lean side.

So does any of that make any sense to anyone? I'm not sure where to go from here

 

I agree with your interpretation, but then I am only an shade tree/arm chair technician.

To me it seems the catalytic converter is not using up the present O2 or the downstream sensor is unable to measure the O2 correctly.

Because it is cheap and has a potential to clear things up I suggest you try a Scotty Kilmer style catalytic converter cleaning:
Put 1 gal (4L, for you Canadians) of Lacquer Thinner (NOT PAINT THINNER!!!) into 1/2 full tank of gas and drive it for about 100 miles (that's 167.8 km for you Canadians). Give it a few good pulls up on the rpm's to blow the contaminants out of the core. That also cleans the O2 sensor surfaces.

 

Those numbers are like Chinese to a Freak Like Me!
I got the Scotty Video on my Favs:

 

hi ...

Do you have the problem with code P0171 ? have u changed the Mass air flow sensor ? Usually the protege 1999 has this problem and it should be changed ... buy from dealership or buy a original one as a used one ... be aware don`t buy the fake and cheap one .

 

Hey guys,

Got tired of so much guess work so I took it into a small shop in town for some diagnostics. They checked fuel pressure, vac leaks and MAF & confirmed that all were okay. All they found was that cylinder 4 had carbon buildup on the spark plug and they are suspecting that the catalytic converter may be plugging up. In other words, you may be correct tanprotege. I'll have to try the laquer thinner clean because a new cat just isnt sensible in a car this old. Sure hate driving with a CEL though... I'll let you know how it turns out.