Possible catalytic converter issue

[JB '98 Sahara]

First time Jeeper, 98 TJ Sahara 4.0, feels like it’s starving for fuel, almost wants to die out when it starts. Thought it was bad gas, but now I’m thinking it’s catalytic converter. Has high miles, I’m learning here, but I’m thinking that’s what the issue is possibly being plugged up? Maybe the rear one at muffler? Anyone have same issue or recommendations for me?

 

[Blondie70]

I'd pull the O2 sensor in front of the cats and leave it out and run it. See if it's ok like that. If so, then U know cats are plugged Good Luck

 

[JB '98 Sahara]

I'd pull the O2 sensor in front of the cats and leave it out and run it. See if it's ok like that. If so, then U know cats are plugged Good Luck

Thank you, I’ll try that. My O2 sensors were replaced already also. Didn’t think of trying that though for this issue.

 

[macleanflood]

What brand of O2 sensors? TJs typically only behave well with NTK or Mopar.

-Mac

 

[CharlesHS]

Check the fuel pressure at the fuel injector rail; the symptoms you are describing could also be low fuel pressure.
There is a schraeder test connection that a fuel pressure test gauge can be connected to for measuring the pressure; the pressure at the fuel rail should be approximately 49 psi.
You can rent or borrow a test gauge kit at most local auto parts stores.

 

[JB '98 Sahara]

What brand of O2 sensors? TJs typically only behave well with NTK or Mopar.

-Mac

I’m not sure, the fella I bought it from had replaced them both right before I picked it up from him. I’m sure from O’reilly’s and a cheaper one. He even sent me with a spare one.

 

[JB '98 Sahara]

Check the fuel pressure at the fuel injector rail; the symptoms you are describing could also be low fuel pressure.
There is a schraeder test connection that a fuel pressure test gauge can be connected to for measuring the pressure; the pressure at the fuel rail should be approximately 49 psi.
You can rent or borrow a test gauge kit at most local auto parts stores.

Ok, thank you. I’m taking all of these notes to start diagnosing! I appreciate your help, this has been frustrating. It also has to warm up before driving. A lot more lately. Doesn’t matter the weather temp either.

 

[macleanflood]

Ok, thank you. I’m taking all of these notes to start diagnosing! I appreciate your help, this has been frustrating. It also has to warm up before driving. A lot more lately. Doesn’t matter the weather temp either.

That sounds more and more like a plugged cat... when you first start your Jeep it should be in closed loop mode...high idle, default fuel tables...when it warms up it goes to closed loop and reads the O2 sensors and starts adjusting the air fuel mixture.

The PO changed the O2 sensors trying to fix the issue and probably made it much worse by using non Mopar/NTK sensors.

-Mac

 

[CharlesHS]

That sounds more and more like a plugged cat... when you first start your Jeep it should be in closed loop mode...high idle, default fuel tables...when it warms up it goes to closed loop and reads the O2 sensors and starts adjusting the air fuel mixture.

The PO changed the O2 sensors trying to fix the issue and probably made it much worse by using non Mopar/NTK sensors.

-Mac

Yeah.... that doesn't sound like a fuel pump pressure problem if he needs to wait until the engine is warmed up before driving....

 

[JB '98 Sahara]

Yeah.... that doesn't sound like a fuel pump pressure problem if he needs to wait until the engine is warmed up before driving....

 

[JB '98 Sahara]

It does have high mileage, and the cats were never messed with that I see. PO documented everything he did on jeep, helps me also. But will have to check into the better O2 sensors, and new cat too. I’m sure I’ll have to replace both front and rear, any suggestions?

 

[macleanflood]

Pull that O2 sensor as suggested...if it's blocked it should help.

-Mac

 

[JB '98 Sahara]

Pull that O2 sensor as suggested...if it's blocked it should help.

-Mac

 

[JB '98 Sahara]

Pull that O2 sensor as suggested...if it's blocked it should help.

-Mac

Thank you very much! I appreciate everyone’s help w this!