Previous owner mysteries: o2 sensor spacers- CAT - Vacuum lines-

[Rotary Minds]

Hi, i bought this dodge 1500 a year ago and am still trying to figure out what the previous owners did to it and iron out any issues. Any Ideas are much appreciated.
1998 RAM 1500 V8 Magnum 5.9 liter / 360 CI engine 4x4, Automatic transmission.

When I bought it there was a check engine light for the upstream o2 sensor and it would not idle for more than a few minutes without dying or nearly dying. I replaced the upstream o2 sensor and found a spacer on it which I had to remove to get the new (longer) sensor to fit. It then would idle fine but i noticed sometimes it would sometimes stutter if idling for over 5 minutes. Just this last week it stopped idling well and a check engine light came on for the downstream sensor which I then replaced.

The downstream o2 sensor also had a spacer which I removed, is there any reason I should put it back on? The truck seems to be running fine for now but I don't want to run into more issues down the road. The exhaust pipe was obviously cut open where the catalytic converter goes which means they did something to the CAT.

If i run in to more issues would getting a new CAT be a good fix? Or maybe the tampering done to the CAT was to compensate for something that was done to the engine?

Only other information I can think that may be helpful is the truck is idling around 700 RPMS and has always had a very deep pronounced sound like it was intentionally modified to sound that way.

Picture of new upstream o2 sensor without spacer installed:

CAT:

Old o2 sensor with spacer:

Unrelated to the o2 sensor issue:
I recently replaced the thermostat because the temperature gauge was only reading about 140 degrees Fahrenheit, after putting a new stock 192 degree thermostat it is up to about 170 so maybe the gauge is off a bit. It has only been getting 12 MPG and I suspect that the low temperature was contributing by causing it to run rich. I'm in Northwest and it is often near freezing in winter and decently warm in summer, Last summer I think it was getting closer to 16 MPG.

I fixed a vacuum leak in the ventilation controls system which hadn't been working, I suspect that there could be more leaks but am not experienced with vacuum systems. Am seeing an open end vacuum hose on right side of engine which runs down to the transmission and 4x4, transmission might be shifting just a little bit rough and 4x4 has been working fine. The suspicious hose is green and runs alongside a white hose, the white hose tee's into ventilation and then runs into engine. Someone mention the hose was a vent but it looks like it is broken off of something, the diagram I have is not detailed enough for me to figure it out.

Pictures of vacuum line stuff:

1998 RAM 1500 V8 Magnum 5.9 liter / 360 CI engine 4x4, Automatic transmission - 143,000 miles Reconstructed title

 

[Okiespaniel]

Gutting the 2in,1out cat is common on pre 1999 2nd gens because the cat was prone to clogging.

The spacers you see were originally sold for older cars who's piston rings were shot and thus were burning oil. They were called non foulers and kept the electrodes out of the oil/gas/air mixture while still providing the spark. They had the effect of raising the plug's heat range to try and keep it clean. They were moderately successful....

I digress, but that's what they did. Their use on oxygen sensors were similar. The intent was A. to provide a temperature range similar to a functioning convertor. B. keeping the electrodes on the sensor out of the flame path and C. fooling the computer that the convertor had not been modified.
Like the original intent to ignite an oil mixture, they were moderately successful. For some they worked perfectly, for others, it was a disaster, and those unfortunate folks ended up replacing the convertor.

So if you start getting CELs related to convertor or the oxygen sensors, you have to put the spacers back in.

 

[Rotary Minds]

Sure enough I now have a code related to the converter...