Engine revs and dies suddenly

M

Mercury

TJ Enthusiast
Joined
Jul 18, 2018
Messages
227
Location
Louisville, KY, USA
Hello,

I just finished a two hour drive without issue. When I started my Jeep to go home I made a few dozen yards before the engine bogged, then came back, bogged, came back. I limped it to a parking lot. I started it again and it idled fine for a few minutes, then it started alternating between trying to die and revving up.

I ran my scanner and got the following codes:

P0138 Heated oxygen sensor 2 bank 1 high voltage

P0132 Heated oxygen sensor 2 bank 1 high voltage

I'm reading online that this could just be a faulty O2 sensor but I've had that before and it didn't have that problem. It also said might be a leaky fuel injector.

Can anyone shed some light on this? I'm currently stuck in a parking lot two hours from home. No check engine light.

1999 Jeep Wrangler 4.0.

Update: started it again, idle is rough but it can move, however my AC panel isn't working. I can't turn on the blower on any selection. I hear a slight hiss when I try to turn on any of the settings but zero output.

Screenshot_20230131_141222.jpg
 
Mercury said:
I just hear the hiss in the cabin, tried to listen for one in the engine bay and didn't hear anything.
Click to expand...

I don't know much about your issue, but if you hear the vacuum leak in the cabin, it could be the black vac line that goes through the firewall, and simultaneously one or both of the vacuum check valves in the engine bay. There is one right at the T where it goes into the firewall (right by the heater hoses) and another just after the port on the rear of the intake.
 
hear said:
I don't know much about your issue, but if you hear the vacuum leak in the cabin, it could be the black vac line that goes through the firewall, and simultaneously one or both of the vacuum check valves in the engine bay. There is one right at the T where it goes into the firewall (right by the heater hoses) and another just after the port on the rear of the intake.
Click to expand...

It's the sound it normally makes when I switch settings on the climate control, but the blower motor is totally dead and I replaced that less than 5k miles ago.
 
hear said:
I don't know much about your issue, but if you hear the vacuum leak in the cabin, it could be the black vac line that goes through the firewall, and simultaneously one or both of the vacuum check valves in the engine bay. There is one right at the T where it goes into the firewall (right by the heater hoses) and another just after the port on the rear of the intake.
Click to expand...

if you hear that vacuum leak constantly i would unplug it from the T fitting and try plugging/capping it, that could be causing your problems !!!!!
 
tr21triton said:
if you hear that vacuum leak constantly i would unplug it from the T fitting and try plugging/capping it, that could be causing your problems !!!!!
Click to expand...

Oh, so when you switch between settings on your panel you don't hear a hiss? Man, that's how mine has been for a decade, I thought that was normal
 
Mercury said:
Oh, so when you switch between settings on your panel you don't hear a hiss? Man, that's how mine has been for a decade, I thought that was normal
Click to expand...

yes for a second, but the way you described it it is constant .
Mercury said:
I just hear the hiss in the cabin, tried to listen for one in the engine bay and didn't hear anything.
Click to expand...
 
tr21triton said:
yes for a second, but the way you described it it is constant .
Click to expand...

Oh sorry, no. I just can hear the momentary hiss, it doesn't last.

It's just weird that the blower is completely out right as the engine starts to rough idle and stall. Don't know if they're connected but it's an odd coincidence. I just need to think of something, I'm stuck two hours from home.
 
  • Like
Reactions: tr21triton
Update: drove it around this parking lot, got it up to about 30 mph, drove fine but it idles really rough. Not entirely sure if it's drivable for long distances or not. When I first start it revs a bit harder than normal. Not sure what this all might mean.
 
Mercury said:
Update: drove it around this parking lot, got it up to about 30 mph, drove fine but it idles really rough. Not entirely sure if it's drivable for long distances or not. When I first start it revs a bit harder than normal. Not sure what this all might mean.
Click to expand...

the rough idle is likely due to the o2 sensor issue. Whether or not that's because of the sensors, the computer, or something in between remains to be seen.

That the blower is affected when you start the jeep feels like a strange wiring problem. The blower isn't connected to the computer or ignition (as far as I know...I'm now wondering if the computer indirectly controls the A/C relay), so my best guess is that there's a short somewhere in the blower circuit. And of course, check fuses.
 
hear said:
the rough idle is likely due to the o2 sensor issue. Whether or not that's because of the sensors, the computer, or something in between remains to be seen.

That the blower is affected when you start the jeep feels like a strange wiring problem. The blower isn't connected to the computer or ignition (as far as I know...I'm now wondering if the computer indirectly controls the A/C relay), so my best guess is that there's a short somewhere in the blower circuit. And of course, check fuses.
Click to expand...

I ended up having it towed and then spending a great deal of time getting home. It's my Jeep mechanic, and he agrees that it's probably the O2 sensors. I'm a little worried that they both went out at the same time, it almost seems like it's something upstream, but we'll see.

I'm going to change the O2 sensors this weekend and see how it goes. It's just so strange that the blower went out at the exact time as the sensors. I drove two hours, everything ran great including the blower, then all went down. Maybe it really is a coincidence.

Oh, forgot to mention, I replaced the oil sending unit very recently, is there any way that could play a factor?
 
Mercury said:
I'm going to change the O2 sensors this weekend and see how it goes. It's just so strange that the blower went out at the exact time as the sensors. I drove two hours, everything ran great including the blower, then all went down. Maybe it really is a coincidence.

Oh, forgot to mention, I replaced the oil sending unit very recently, is there any way that could play a factor?
Click to expand...

I agree, that's super sus. Everybody here has their go-to likely culprit. Mine is wiring. I'm pretty sure the blower wiring is completely inside the cab/behind the dash, so it seems unlikely that anything you did under the hood would have had an effect there. But the oil pressure wiring is part of the main harness which includes the 02 sensor wiring, so moving stuff around certainly could have been the straw the broke the camel's back. I think I would chase down the blower problem first, because it has way less stuff tied to it.

Friend bought a TJ in August. Drove it a bunch around town and even wheeled it. Parked it, did an axle swap, and when we got done it would crank but not start. Didn't make any sense, we didn't touch anything that would have created an issue. Ended up opening the harness, and found several wires with missing insulation. Repaired them, started right up. My point is that you can have latent wiring issues hidden in the harness that for no reason will decide to emerge from their dormant state and ruin your day. Whether or not it's your problem, I can't say. But I've never opened a jeep harness and DIDN'T find issues.
 
afitzray97 said:
Maybe a clogged/rusted catalytic converter choking downstream air flow?
Click to expand...

The cat may possibly be absent...

hear said:
I agree, that's super sus. Everybody here has their go-to likely culprit. Mine is wiring. I'm pretty sure the blower wiring is completely inside the cab/behind the dash, so it seems unlikely that anything you did under the hood would have had an effect there. But the oil pressure wiring is part of the main harness which includes the 02 sensor wiring, so moving stuff around certainly could have been the straw the broke the camel's back. I think I would chase down the blower problem first, because it has way less stuff tied to it.

Friend bought a TJ in August. Drove it a bunch around town and even wheeled it. Parked it, did an axle swap, and when we got done it would crank but not start. Didn't make any sense, we didn't touch anything that would have created an issue. Ended up opening the harness, and found several wires with missing insulation. Repaired them, started right up. My point is that you can have latent wiring issues hidden in the harness that for no reason will decide to emerge from their dormant state and ruin your day. Whether or not it's your problem, I can't say. But I've never opened a jeep harness and DIDN'T find issues.
Click to expand...

That's wild! Weird how unrelated stuff can just break down together for no apparent reason. Did everything keep working fine in his rig after that?

Well I just replaced the O2 sensors and it seemed to fix most of it but a couple of times while I was warming it up if I press the accelerator and then quickly let off the RPMs would drop down to below 500 and it would try to stall. The problems seem to fade out as I kept running it and there are no longer any O2 codes from the computer, but still weird.

Tomorrow I'm going to pick the Jeep up (still in my mechanics parking lot) and drive it the 2 hours home and see how it runs. Fingers crossed. If anyone has any input as to why it may have tried to stall like that please let me know, I'm a little concerned.
 
Mercury said:
The cat may possibly be absent...



That's wild! Weird how unrelated stuff can just break down together for no apparent reason. Did everything keep working fine in his rig after that?

Well I just replaced the O2 sensors and it seemed to fix most of it but a couple of times while I was warming it up if I press the accelerator and then quickly let off the RPMs would drop down to below 500 and it would try to stall. The problems seem to fade out as I kept running it and there are no longer any O2 codes from the computer, but still weird.
Click to expand...

Yep, 100% fine after that. Well, never mind blowing out the rear ring & pinion last weekend.

Your bog down issue is of interest to me, we’re working on an XJ and it is doing exactly that.
 
Drove it the full two hours last night without issue. The rumble of the idle was a tad different than normal but maybe that's just because failing O2 sensors having been making it different for a while. Fingers crossed but no issues.

Now to figure out why my 6 month old, sub 5k miles blower motor just went out on me.
 
Top Bottom
Back