5.9 FI Magnum swap in 73 swinger

player1up said
My 99 has 2 upstream sensors as well and noticed the same issue, but if I ran in open loop, it would load up at idle. I'm planning on leaving off the downstream sensor as I've read that it only monitors how effective the cat is.
Does your harness have letters on the O2 wires? Mine has L,R ( maybe 1 and 2, it's been a while since I've been up under the car ) on the upstream wires and nothing on the downstream wire. It's like a wrapped label on the harness side close to where it plugs into the sensor...oh, you are running a different ECM, but does the harness have 2 upstream O2 plugs?

haha, well.... my system is officially a mutt..... Its the 98 Jeep Grand Cherokee Harness. I tried to repair the C1 connector cause it seemed to have a loose connection. Turns out that my Jeep's PCM was bad so I ordered a Mopar Performance one from a guy online. I also had to repair the C1 connector so I went to the boneyard and cut one out of a 99 dodge truck harness (thinking color would be the same) and spliced it into the jeeps wiring harness. It does luckily have A24 and A26 (26 is not hooked up at this point in time) upstream O2 signal wires. A25 is downstream and, it is for emissions only.

I would check your fuel pressure, from what I've been reading it should not load up if just running open loop. It runs off of a stored fuel map that is a bit on the rich side. If the fuel pressure is too high it can run rich, or if the injectors are leaking. Now..... it does need full exhaust or it will load up. Not sure as to why, but my car did the same thing until I had the exhaust done. I have the sites I found online about that situation, ill shoot them over to you when I get home tonight. You could also google P0137 (i think)