Recurring P0159,P0139 SLow resp.O2 circut

[cat-black]

2004 3.7 5spd Manual 130,000 miles
Read me! Bought this jeep a month ago. Had slow response from rear 02 sensors on each side, so I did the following.
Plugs (bosch), oil change, cleaned IAC, rust sprayed the ground straps, checked all fluids. Ran some inj. cleaner through.
Checked all vacuum lines.
The codes continued.... in the meantime i'd smell some heavy catalytic stinks when driving around... So I put in two new downstream O2 from Denso. Reset MIL and, yes, codes came back. Sometimes left bank, sometimes right. Sometimes accompanied by P0259 fuel trim system too lean.
So I replaced the upstream O2 sensors also.
Continued driving it, cleaned the pcv system hoses etc, and replaced the pcv valve, codes still come up.
Bought the obd scan lx, and Now i watch fuel trim, and 4 O2 voltages on my phone, in real-time.
(sorry for the story....)
Only when driving highway or straight sections of 80km road, the bank 2 upstream will start to hang high, it wont cycle like it should. which causes ecm to trim fuel, and sends the downstream down in voltage.
I can break the issue by putting the clutch in and revving it up, that usually wakes up the upstream sensor.
Now what gets me is that it's been the same problem since i bought the damn thing, and nothing ive done has helped.
any thoughts?

 

[cat-black]

On the list to check again - plugs, O2 sensor wiring, fuel pressure. anything else?
thanks in advance.....

 

[Birdman330]

Take a temp sensor to the front and rear of the cats, if temps are hotter to the pipes going to the cats than behind the cats. Possible one is plugged.

 

[tjkj2002]

yep looking at that pic the 1st thing in my mind is the cat's are going.Once warmed up those downstream O2's should never go outside of 0.4-0.6 volts.






Oh and trash those bosch plugs,not good.

 

[ltd02]

May be more snake oil but could give this a try:

Cataclean original - CATACLEAN®ORIGINAL

Not cheap but I know a couple of people said it worked for them. Cheaper than a cat replacement but may just be a bandaid.

Oh and the Bosch plugs are trouble.

 

[tjkj2002]

May be more snake oil but could give this a try:

Cataclean original - CATACLEAN®ORIGINAL

Not cheap but I know a couple of people said it worked for them. Cheaper than a cat replacement but may just be a bandaid.

Oh and the Bosch plugs are trouble.

That $2 bottle of Lucas cleaner does the same thing, absolutely nothing.




There is no repairing of a cat,once it starts going downhill it's done and nothing can change that fact.

 

[cat-black]

All valid points, but I see the upstream staying high as well, and that's what sends everything for a ****. I'll check temps with an infrared gun, and what plugs? Just reg old NJK?

 

[cat-black]

Temps on cats are 350 F before and 375 or more after the cat.

 

[ltd02]

There is no repairing of a cat,once it starts going downhill it's done and nothing can change that fact.

Figured it wouldn't save a bad cat but did help a couple people get through emissions. Thought it might be worth a shot. I personally don't use anything except for occasional Techron.

All valid points, but I see the upstream staying high as well, and that's what sends everything for a ****. I'll check temps with an infrared gun, and what plugs? Just reg old NJK?

Yes on the NGK plugs.

 

[tjkj2002]

Temps on cats are 350 F before and 375 or more after the cat.

Cats are doing little to nothing,there on there way out.You should see at least a 100 degree+ difference.

 

[cat-black]

Ok thanks folks. I'll likely get stealership cats I can get a discount. I'll post some pics soon of the vents and oil catch can I did.

 

[cat-black]

One more thing, if anyone knows what their "normal" O2 sensors voltages are... Someone mentioned .5 to .6? On downstream.

 

[ltd02]

One more thing, if anyone knows what their "normal" O2 sensors voltages are... Someone mentioned .5 to .6? On downstream.

Mine bounce around quite a bit, they are supposed to cycle or loop (high and low) but typically spend time around 0.5V. Unless you have a very fast scanner or an oscilloscope I believe it's tough to see the loop. I guess 0.45 is optimal. All four of mine do this.

 

[tjkj2002]

Mine bounce around quite a bit, they are supposed to cycle or loop (high and low) but typically spend time around 0.5V. Unless you have a very fast scanner or an oscilloscope I believe it's tough to see the loop. I guess 0.45 is optimal. All four of mine do this.

At full operating temp and a steady cruise speed(say 65mph) the up-stream O2's should cycle from around 0.1v-0.9v(with good scanner will see cycle very fast),the down stream O2's should hover in the 0.4v-0.6v range(up to 0.7v is okay still) but should never cycle fast and "follow" the up-stream O2 sensors.Steady cruise speed is when the PCM monitors the O2's and your voltages can swing wildly on accel and decal(city type driving).




On decal you can see the down stream O2's spike above 0'8v since the fuel is cut off from the cylinders and will see them drop to almost 0v when accelerating due to the excess fuel added for acceleration.

 

[ltd02]

At full operating temp and a steady cruise speed(say 65mph) the up-stream O2's should cycle from around 0.1v-0.9v(with good scanner will see cycle very fast),the down stream O2's should hover in the 0.4v-0.6v range(up to 0.7v is okay still) but should never cycle fast and "follow" the up-stream O2 sensors.Steady cruise speed is when the PCM monitors the O2's and your voltages can swing wildly on accel and decal(city type driving).

On decal you can see the down stream O2's spike above 0'8v since the fuel is cut off from the cylinders and will see them drop to almost 0v when accelerating due to the excess fuel added for acceleration.

I've really only watched them while idling or revving in park. My scanner is not very sophisticated or fast enough to see the whole cycle but based on the refresh rate and numbers I see it seems like it's acting exactly as you describe. Upstream seem to have a broader range than the downstream. I do see the big changes if I rev the engine and the downstream drop off when doing so.

When my one upstream went on my Avenger over the summer it would hang at 0.8-0.9 all the time and set a CEL and eventually had a hard misfire. Finally just changed it and hasn't happened since.

Thanks for the great description. I'll definitely save this for future reference.

 

[cat-black]

Yep. Great info
From all that looks like my sensors are doing the right thing.the computer runs self tests as well its part of the monitors, that's what I think is happening when the upstream stays high for a bit. I've found that my ecm p/n is not the latest. Mine is 56044209AH. It updates to AI.

 

[cat-black]

This is the list of computer or ecm p/n and update ones

 

[cat-black]

Just an update. The dealership could not flash because they didn't have the older version of flash equip. Said that some d-ships still might have it.
Upstream sensor still hangs high on highway cruising, and if I don't catch it, it eventually throws a code. Not bias to either bank. Still working on it........