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Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go hereXJ (84-01)
All OEM related XJ specific tech. Examples, no start, general maintenance or anything that's stock.
I am not aware of how an O2 issue could be generated in the exhaust system, unless you had an obvious (audible) exhaust leak
if there is an air leak in the intake system, old skool basic diagnosis applies
you may even want to check Youtube on using smoke to test for a leak on the intake side...especially if you smoke, cigs, cigars, or you might be needing a herbal remedy by now
maybe I can rig up a makeshift pump of sorts and push some smoke into there. Does this test usually work Well?
old skool basic diagnostic, does propane count and is this a good choice?
I've tried spraying crc (50 state formula) carb cleaner over all vacuum lines, against the block where the manifold mates, with no luck of stalling the engine/ rpm increase or indication of a leak. Maybe it's the wrong stuff, would propane be a good option?
Your upstream O2S should not be 0V. It should be reading every second or so and bouncing. You sure you plugged everything back in?
Yes everything was plugged back in. I have been digging through the fsm from cruiser, I'm not sure if some of it is missing, some other diagnostic requires a other drive train manual.
here's the latest readings on the scanner once it started running bad.
what happens if you unplug the front O2 sensor with the engine running?...if nothing happens, the O2 sensor is likely cactus...yr truck is throwing an O2 sensor code, is it not?
what happens if you unplug the front O2 sensor with the engine running?...if nothing happens, the O2 sensor is likely cactus...yr truck is throwing an O2 sensor code, is it not?
pull it before it warms up or when it starts running poorly?
did you mean if nothing new happens its bad?
Last edited by 4x4jeepmanthing; 03-02-2019 at 06:36 PM.
pull it before it warms up or when it starts running poorly?
did you mean if nothing new happens its bad?
Your jeep ignores the O2 sensor while it is warming up. This is when it is running "open loop" and fuelling off a default map. Once it is up to temp, the computer starts using the O2 sensor to determine how rich or lean the engine is running. If the LTFT gets pegged all the way rich or lean, the two prime suspects are a big vacuum leak (you'd probably be able to hear it) or a bad reading from the upstream O2.
I had a similar issue with my jeep. It ran fine open loop but misfired and lost power when warm. A new O2 fixed it, but check your wiring first.
Another thought, are you using the correct sensor for your year engine and ECU? I don't know if they changed over the years.
The 02s in it now are Bosch, my jeep is a 99. The new engine is a 92 block with all 99 parts added on, other than new plugs and banks header. Nothing should have changed so the 99 ecm should be reading off the correct sensor, unless like you said somethings wrong with the sensor.
I swapped everything over, hooked up the battery and turned the key on, that's it.
tank has about a 5th in it, pump is Bosch, injectors 4hole bwd.
I'm tearing into everything I can read to learn and try to fix this, but I'm falling on my face pretty hard repeatedly. I need to make a smoke tester or test vacuum leak with a propane torch.
if I unplug the sensor will it stay in open loop?
Last edited by 4x4jeepmanthing; 03-03-2019 at 02:04 AM.
So here is what I would do if presented with your vehicle as a technician;
apply a vacuum gauge, which would highlight the following problems..air leak, timing issue, ANY internal mechanical problem
A vacuum gauge is like $20, or probably free to rent over there. An indispensable tool for diagnosing any air pump (such as an IC engine)
Once the engine is believed to be ok for the above test, replace any sensors that are throwing a code (after checking wiring)..no ifs, no buts, got a code, replace it
one at a time, testing in between
do you have 2 x O2 sensors ?
a PO has cut the wires on my rear O2, the sensor looks seized, generates a P0138 code, but does not trigger the check light
fault finding must be methodical or you will chase your tale
So here is what I would do if presented with your vehicle as a technician;
apply a vacuum gauge, which would highlight the following problems..air leak, timing issue, ANY internal mechanical problem
A vacuum gauge is like $20, or probably free to rent over there. An indispensable tool for diagnosing any air pump (such as an IC engine)
Once the engine is believed to be ok for the above test, replace any sensors that are throwing a code (after checking wiring)..no ifs, no buts, got a code, replace it
one at a time, testing in between
do you have 2 x O2 sensors ?
a PO has cut the wires on my rear O2, the sensor looks seized, generates a P0138 code, but does not trigger the check light
fault finding must be methodical or you will chase your tale
where do I hook up said gauge? I guess a more appropriate question would be, are there best spots for hooking it up?
Last edited by 4x4jeepmanthing; 03-03-2019 at 09:27 PM.
anywhere that has unported manifold vacuum, havent done it on an XJ, other cars..look on the manifold for hose that can be pulled or teed (brake vacuum resevoir? )
maybe I have even seen it in the FSM??
google is your friend, including download a interpretation chart....thing is a vacuum leak (or other mechanical issue) will jump right out at you
at idle, the needle MUST be steady, = engine good, not wavering or jumping around
News,
we got to looking over the whole engine, vacuum was a bit low but steady. We pulled plugs, Covered in soot. Compression test of all cylinder passsed very well.
Tps does show a dead spot on the blue driver when sweeping, the multi meter does Not show this, in fact it looks good on a digital. Analog for sweep or just don't test. We left the sensor because the dead spot was at cruise sweep, I never had any issues before. The p0122 does still read. I'm betting a new tps would be good, but it's running fine anyhow.
tried swapping 1-2, 5-6 injector plugs, nada. Then the bluedriver showed little signal from the upstream Bosch 02. Threw in new Ntk 02, and pulled out new platinum autoliteplugs APP985, swapped in my old champs. Once we did this she purred flawlessly.
I'll start another thread because I have tried to move it today a d the 99 aw4 buzzed shifting up to park.
if anyone has any questions for input I'm happy to add detail, thank you.
Last edited by 4x4jeepmanthing; 03-06-2019 at 02:43 AM.
News,
We pulled plugs, Covered in soot.
tried swapping 1-2, 5-6 injector plugs, nada. Then the bluedriver showed little signal from the upstream Bosch 02. Threw in new Ntk 02, and pulled out new platinum autoliteplugs APP985, swapped in my old champs. Once we did this she purred flawlessly.
.
the old O2 sensor could have caused permanent rich running, sooting the plugs..did it get rid of yr O2 related code?
02-28-2019, 08:49 AM
