High idle, BS codes

[Minty]

So the Jeep is idling around 1100-1300 RPM, from the time it starts to the time its warm and I shut it off. Other than that, it's running well.

Not sure if it's related but, I'm getting a CEL that's coming up as P0138 and P0141 (both: bank 1 sensor 2).
Possible causes are:
138- O2 sensor
-Running rich or lean
-Misfire
-Fuel pressure very high or low

141-O2 sensor
-O2 sensor connection
-Circuit fuse

I only have one o2 sensor, and no cat. Are these codes just for the non-existent downstream sensor? I've replaced my o2 sensor twice to be sure.

I checked my exhaust pipe, and its got quite a bit of soot built up. I'm thinking it's getting too much fuel and running rich? Fuel pressure regulator? Only problem is, on a 96 I guess it's on the pump and has to be swapped out as one unit... which is about $200... I just checked the plugs and they look fine. I'm about to buy a fuel pressure tester to start checking that, just wanted to check with my resident guru's to see if I'm heading the right direction. Oh, and I've already swapped the IAC.

Levi

[4.3LXJ]

One will be for the downstream sensor for sure, the 141 code. You may also have a bad upstream sensor. If it hasn't been changed in forever, better change it too. As for idle, pull the Idle Air Control on the throttle body and clean that

[Minty]

Up-stream has been changed twice within the last 20 miles or so.

Changed the IAC previously while working a stumble issue so that's pretty much new as well.

[4.3LXJ]

But you are getting a code for the upstream. Better check the wiring. Did you clean that IAC port?

[Minty]

But you are getting a code for the upstream. Better check the wiring. Did you clean that IAC port?

I'll go check into the wiring, the connector looked good when I replaced it. I also removed and cleaned the entire TB.

[Minty]

So I was just out tinkering with the wiring, everything looked good so I got to thinking... I disconnected the plug from the TPS while running and it instantly started idling back down where it should be. Plugged it back in and it shot back up. Does that point to a bad TPS? And then the o2 codes point towards the missing down-stream sensor?

[4.3LXJ]

Do you have a cat and a pipe behind it?

[Minty]

No cat, just pipe with a muffler.

[4.3LXJ]

Where is the O2 in relation to the muffler?

[Minty]

O2 sensor is at the front of the exhaust pipe, before the muffler.

[4.3LXJ]

Here are my thoughts on that O2 sensor. They only show codes if they have a break in the wiring or the heater in them is shot. I am assuming you have a three wire sensor in. I know you probably don't want a cat, but the whole system was designed to have one. A properly functioning high flow cat will get rid of two of those codes if the wiring is intact

[Minty]

I was thinking I may need that as well. Do you think this is the source of my high idle though? I thought as long as you have an upstream o2 it will run fine but still throw a code for the downstream, although not having a downstream doesn't affect how it runs...?

[4.3LXJ]

In theory. But IIRC there have been isolated cases of not having that sensor made them run whacky. There is a difference in having a code for a bad sensor and not having one at all.

[Minty]

Ok, here's my conclusion...
The O2 codes and the high idle were not directly connected. What ended up curing the higher idle was actually replacing the TPS! What I'm thinking was going on was the O2 codes being thrown were just for the removed down-stream O2 sensor and had no (noticeable) impact on engine performance.