Motor has occasional hesitations/sputtering

2000 4.0 auto 4x4

My Jeep has occasional hesitations where it feels like the motor cuts out for a second and then acts normal again. And by occasional I mean at least once every other time I drive it. One time it was bad enough that the motor died and I coasted off the freeway, but it fired right up and drove home fine.


My Check engine light has been on, and was originally telling me one of my O2 sensors was bad. Cleared it and it came back saying all 4 were bad, cleared it again and it was saying only the upstream sensors are bad. (I love computers :flamemad I replaced both upstream sensors with Bosch units from O'reillys auto. After clearing the codes again now it says 1 downstream and 1 upstream are bad. After replacing both upstream sensors I am still getting the original problem. I am heading to Utah from SoCal in 2 weeks and I need to be able to depend on this Jeep getting me there and back and enjoying the Utah scenery while I'm there.

Any help/suggestions/pointers would be much appreciated. I really would like to get this solved. Thanks!

Maybe check the ground (G101) on the right side of the engine block just aft and above where the oil filter is. This is the ground stud location to supply ground to pin 2 of each o2 sensor.

bshack said:

Maybe check the ground (G101) on the right side of the engine block just aft and above where the oil filter is. This is the ground stud location to supply ground to pin 2 of each o2 sensor.

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Thanks for the suggestion I'll take a look at this today.

Many say that Bosch O2 sensors and Jeeps do not play well together. NTK is the original equipment and are available at NAPA and many other parts retailers.

Unexplained stalling is most often caused by a failing Crankshaft Position Sensor.

Tim_MN said:

Many say that Bosch O2 sensors and Jeeps do not play well together. NTK is the original equipment and are available at NAPA and many other parts retailers.

Unexplained stalling is most often caused by a failing Crankshaft Position Sensor.

Click to expand...

Thanks for the info. Weird to think brand new sensor wouldn't work well, but I have read that while searching. If I knew buying the NTK sensors would solve my issue I wouldn't mind spending money on them, its just if I spend money on them and it doesn't fix the issue is the problem.

Would a failing Crankshaft Position Sensor trigger a code? Most of the codes I have been getting all deal with the O2 sensors.

Thanks!

bshack said:

Maybe check the ground (G101) on the right side of the engine block just aft and above where the oil filter is. This is the ground stud location to supply ground to pin 2 of each o2 sensor.

Click to expand...

4jeep4 said:

Thanks for the suggestion I'll take a look at this today.

Click to expand...

I checked the ground and it looked good. I took it off and cleaned it all up anyways and took some sandpaper to it. We'll have to see if it helps.

A failing CPS seldom sets a trouble code. If you have O2 sensor codes, you have O2 sensor issues. If those issues are caused by a Bosch O2 sensor IDK, but I always use NTK O2 sensors.

Tim_MN said:

A failing CPS seldom sets a trouble code. If you have O2 sensor codes, you have O2 sensor issues. If those issues are caused by a Bosch O2 sensor IDK, but I always use NTK O2 sensors.

Click to expand...

Thanks for the info. Yesterday while driving the Jeep randomly died on me. But it fired right up after stopping and getting it in park. There should be no reason O2 sensors would cause this correct? But possibly a bad CPS could cause this? Any specific brand for a CPS sensor I should get?

The only codes present are dealing with O2 sensors currently.
Thanks again.

Buy genuine Jeep CPS.

Cheap crappy "Lifetime Warranty" parts are often out of specification, or even failed, right out of the box. Many times they have a short service life before they fail. Always buy top quality replacement parts and genuine Jeep sensors. Numerous threads detail long and frustrating searches for a "problem" that ended up being cured with genuine Jeep repair parts.

Cheap parts are cheap for a reason.

You may want to check your wiring harness under t/ hood for burnt insulation. Not a particularly fun repair. Should you be able to translate into English give it a consideration. Ciao.

Well I ended buying all new NTK O2 sensors yesterday. Put them in and the check engine light was cleared until this afternoon and is saying all my sensors are bad. Very very frustrating. I inspected all grounds and pretty much all the wiring.

I'm sensing the same issues that's saying my sensors are bad is the same thing that's causing my hesitation/stalling. They started happening around the same time. It's very frustrating to say the least. Any other ideas or suggestions I'm very much appreciated. I plan on replacing my cps as soon as the dealer gets it in stock. I want to be able to rely on this for my trip. Thanks again.

Well the only thing to do after you think you tried everything is to do it again right.. I swear I checked my fuses but maybe my mind made that up or the fuse popped in the past couple days since I have looked. The o2 heater fuse was burned out, so it gave me motivation to trace all the wiring again to see if I could find a problem. On the 2nd downstream o2 sensor I found this on the connector coming off the wiring harness...

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I think I was just focusing on the wires coming off the o2 sensors not the connector wires coming from the Jeep, as you can see the connector was covered in oil/grime and when I cleaned it off the 4 wires where pretty much all bare and against each other, I'm assuming and hoping this is my problem. Either way it needs fixed.

My plan is to splice in a new connector as I (luckily) have a spare wiring harness I can pull from. I hope this is my issue that is causing my sensors to not work along with causing my Jeep to stall and hesitate. So even though I bought a new CPS I might hold off installing it just to see if this was the original problem or not.

**UPDATE** Well the fix above fixed my O2 sensor issue but the original problem is still there. The Jeep seems to sputter/die when going uphill with more of a load on the motor most of the time not all the time though.

I replaced the CPS (OEM part) already and the problem still is there.

I'm beginning to wonder if its a fuel problem. Maybe filter or something?? Any other suggestions or people that have had similar problems?

Thanks!

Test the fuel pressure. Rent a tester at the parts store. You should have 49 +/-5 psi fuel pressure.

Test Coolant Temperature Sensor.

When my jeep was sputtering it was a spark issue. Is there a way to test coil packs?

Thanks guys I'll check these all out.