Intermittent cutout/studder right off idle.

[Dickinson County Comanche]

Hello all, my Jeep has developed the interesting quirk of a very intermittent issue where the engine falls on its face while under very light throttle inputs. If I give it more gas, it’ll rev up no problem, or if I go back to idle it’ll idle fine. I deleted the EGR believing it was the problem however it has remained afterwards. TPS maybe?

[pizzaman09]

Check to see if all of your header nuts are tight or even there.  Sounds like a small vacuum leak to me.

[speeding_infraction]

Check fuel pressure

[M.T.Hands]

Man, off idle like that sounds like something "dirty" with the Idle circuit, I'm very new to this vehicle, but my 04 wrangler had a messed up TPS and it would not idle but definitely could be vacuum or fuel pressure related

 

[89 MJ]

Here’s Cruiser’s thread on adjusting the tps:

And you might as well give the throttle body a good cleaning too:

 

[Dickinson County Comanche]

On 10/13/2024 at 2:29 PM, TurboedMJ said:

Check fuel pressure

It’s not down on power, and when I floor it when it’s doing it the truck picks right back up, so I don’t think it’s fuel system related. Pump is only 2 years old.

[Dickinson County Comanche]

On 10/13/2024 at 9:23 PM, M.T.Hands said:

Man, off idle like that sounds like something "dirty" with the Idle circuit, I'm very new to this vehicle, but my 04 wrangler had a messed up TPS and it would not idle but definitely could be vacuum or fuel pressure related

 

My idle circuit isn’t working properly so I have it disconnected. It’s been that way for ~2 years now.

[Ωhm]

O2S with slow response time. O2 is a maintenance item.

[Dickinson County Comanche]

12 minutes ago, Ωhm said:

O2S with slow response time. O2 is a maintenance item.

What’s it’s supposed to be like? I have a snap-on scan tool hooked to it right now looking it over. 
 

Oxygen sensor was also new 2 years ago, it’s an NTK unit.

[Dickinson County Comanche]

Pretty sure the Coolant temp sensor is no good. 

[Dickinson County Comanche]

13 minutes ago, Ωhm said:

O2S with slow response time. O2 is a maintenance item.

Seemed to react pretty snappy. Went from ~2.2V at idle/upon acceleration to ~4-5V upon decel 

[Ωhm]

O2 (V) seems frozen at idle. Should switch rapidly between 0.5 and 4.5. Rapidly like at the speed of light. Coolant sensor is trashed, or wire is your problem.

[Dickinson County Comanche]

4 minutes ago, Ωhm said:

O2 (V) seems frozen at idle. Should switch rapidly between 0.5 and 4.5. Rapidly like at the speed of light. Coolant sensor is trashed, or wire is your problem.

It’s in open loop, if that makes any difference. Very rarely does it ever enter closed loop. Wires looked fine going to the sensor. It’s a pretty cheap old thing, so it’s probably that coolant sensor itself that’s bad.

[Ωhm]

With that O2 and maybe that Coolant sensor, it can't go into Closed Loop.

[Ωhm]

Check O2S heater circuit for continuity. Looking for ≈5-7 Ω's.

[Dickinson County Comanche]

3 minutes ago, Ωhm said:

With that O2 and maybe that Coolant sensor, it can't go into Closed Loop.

Even with it running ok it’s almost never entered closed loop. I almost wonder if the computer isn’t faulty a little bit. Ive used it fine without it entering closed loop but having the iac disconnected is a bit annoying when it’s cold.

[Ωhm]

Sound to me like the ECU is doing what it's suppose to do. Open Loop.

[Dickinson County Comanche]

2 minutes ago, Ωhm said:

Sound to me like the ECU is doing what it's supposed to do. Open Loop.

Now that I’m thinking on it more, I think it’s that O2 sensor. I was trying to delete my EGR valve and when I removed it I dropped it (about 3-4”) so I almost wonder if that didn’t break it. I don’t believe I remember feeling the issue before then, so it makes the most sense to me now.

[Ωhm]

Key OFF. Disconnect O2S. At the sensor measure ohms between C229_A and C229_B. Look for 5-7 ohms.

 

If good, then signal side of sensor is bad because it's just not switching at idle.

[eaglescout526]

Closed loop will let the engine run more efficiently and see your mileage improve. 
open loop is full of defaults for the engine to just run and drive vs what closed loop does. 

[Dickinson County Comanche]

8 minutes ago, Ωhm said:

Key OFF. Disconnect O2S. At the sensor measure ohms between C229_A and C229_B. Look for 5-7 ohms.

 

If good, then signal side of sensor is bad because it's just not switching at idle.

I am showing 0 (or near 0) ohms between A & B. About 4 between C and B.

[Ωhm]

Looks like O2S heater element (A-B) is shorted together internally. No heater.

[Dickinson County Comanche]

Great. Any leads as to where that would maybe be at?

[Ωhm]

It's internal to the O2S itself. Part of the O2S.

[Dickinson County Comanche]

That was on 

1 minute ago, Ωhm said:

It's internal to the O2S itself. Part of the O2S.

Wait so am I checking the sensor’s connector or the trucks connector? I got 0 ohms at the trucks connector since it was the one that matched the diagram