Running Rich, need OBD-ii live data advice.
Herp Derp Jerp
Joined: Nov 2011
Posts: 18,251
Likes: 17
From: Parham, ON
Year: 1999
Model: Cherokee
Engine: 4.0L OBD-II
For what it's worth on my 1999 and 2001 XJs, and even my Volkswagen, the throttle % normally reads at 17% when shut. I believe this is a standard "minimum" for OBD-II so the PCM can tell if there's an open circuit towards the TPS.
STFT is a negative number so the PCM knows it's dumping too much fuel and is trying to pull it back. But obviously it can't. But why is LTFT 6??
I agree with CCKen that you should be running NTKs - lots of people report problems with Bosch and Denso units on OBD-II XJs. Before you do that though inspect all of the harness wiring, refresh the engine bay grounds (bad grounds will make sensor output useless).
If problems still exist after that I'd be wondering about the fuel system.
Some more data would be appreciated too like IAT.
Have you tried dumping the adaptive memory in the PCM to reset LTFT? Disconnect battery and do some fancy dance... can't remember what it is.
STFT is a negative number so the PCM knows it's dumping too much fuel and is trying to pull it back. But obviously it can't. But why is LTFT 6??
I agree with CCKen that you should be running NTKs - lots of people report problems with Bosch and Denso units on OBD-II XJs. Before you do that though inspect all of the harness wiring, refresh the engine bay grounds (bad grounds will make sensor output useless).
If problems still exist after that I'd be wondering about the fuel system.
Some more data would be appreciated too like IAT.
Have you tried dumping the adaptive memory in the PCM to reset LTFT? Disconnect battery and do some fancy dance... can't remember what it is.
Thread Starter
Junior Member
Joined: May 2010
Posts: 47
Likes: 0
From: Kalispell, MT
Year: 1998
Model: Cherokee
Engine: 4.0 with high flow cat and Dynomax exhaust, bored over TB, custom cold air intake, 4 hole injectors
I agree with CCKen that you should be running NTKs - lots of people report problems with Bosch and Denso units on OBD-II XJs. Before you do that though inspect all of the harness wiring, refresh the engine bay grounds (bad grounds will make sensor output useless).
Some more data would be appreciated too like IAT.
Have you tried dumping the adaptive memory in the PCM to reset LTFT? Disconnect battery and do some fancy dance... can't remember what it is.
Some more data would be appreciated too like IAT.
Have you tried dumping the adaptive memory in the PCM to reset LTFT? Disconnect battery and do some fancy dance... can't remember what it is.
I have replaced the coolant temp sensor and it seems to read accurate accord to laser temp cage at thermostat housing. The AIT also seems to be fairly accurate. It shows 70 here lately at cold start, which has been within a couple of deg. of outside air temp. Once warmed up it is usually showing 120 deg as all that engine heat gets trapped under the hood.
I have disconnected the battery and turned the head lights on and off trying to get any residual energy drained. Let it sit for about 10 min while I checked my t-stat for the proper temp unit and changed out some coolant. Then plugged it back in. Saw no difference in the way it was running.
Newbie
Joined: Nov 2023
Posts: 1
Likes: 0
98’ Jeep Cherokee 4L 2WD - System Too Lean Bank 1
98' XJ 4.0 AW4 with 155k on it. An on going issue for the last couple of years. Running rich to the nose yet occasionally throws a running lean code on bank 1. Now it runs rich to the point of spitting droplets of gas out the tail pipe and stalling at stops after it has warmed up. Goes down the freeway fine however.
I replaced the upstream O2 sensor a couple of weeks ago, with no noticeable difference. Looking for ideas on a fix. I have had a couple people guess a bad computer....
With Innova scan tool I get this info
Cold (initial start up)
upstream read .4 - .75
downstream reads .76
Engine at 192
upstream reads 0.00 - .88 (jumping quickly with nothing in between)
downstream reads 1.0 solid (way rich)
STFT remains -4.7 to 0 hot or cold
LTFT remains 6.0 hot or cold
A couple other odd things I noticed. Even when warmed up it remains in CL (closed loop). Shouldn't this have changed to open loop?
Also the TPS reads 15% even at idle. That doesn't make much since, but I have gotten that reading for a couple of years. Is this correct or another source of trouble?
I replaced the upstream O2 sensor a couple of weeks ago, with no noticeable difference. Looking for ideas on a fix. I have had a couple people guess a bad computer....
With Innova scan tool I get this info
Cold (initial start up)
upstream read .4 - .75
downstream reads .76
Engine at 192
upstream reads 0.00 - .88 (jumping quickly with nothing in between)
downstream reads 1.0 solid (way rich)
STFT remains -4.7 to 0 hot or cold
LTFT remains 6.0 hot or cold
A couple other odd things I noticed. Even when warmed up it remains in CL (closed loop). Shouldn't this have changed to open loop?
Also the TPS reads 15% even at idle. That doesn't make much since, but I have gotten that reading for a couple of years. Is this correct or another source of trouble?
Fuel System 1 = CL
Fuel System 2 = —
Load PCT = 4.3%
SHRTFT1 = -0.8% / -3.1%
LONGFT1 = -2.3%
MAP = 10.6
SPARKADV = 15.5
TP = 15%
02SB1S1 = 0.5V
SHRTFTB1S1 = -4%
02SB1S2 = 0.18V
SHRTFTB1S2 = 99%
Ive fixed so far on this:
leaking radiator, clogged cat, and Fuel filter
Intake lines seem good and it doesn’t look like a head gasket issue to me.
If someone knows how to read those codes and see’s something wrong could you please let me know so I can fix it?
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