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TJ shuts off while idling


silv1010

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Joined
Mar 17, 2021
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3
Location
New Jersey
hi guys new here n would appreciate the help

my jeep is dieing out on me when im idling. this would happen when the engine is already warmed up (driving 15mins) and im at red light the engine will just shut off. luckily it doesnt die on me when im driving esp around 50mph but when im just going slwo (5mph) i can tell my engine is about to give. so when it shuts off i surprisingly can atleast turn it back on but if i dont give it gas and shift to drive fast enough the engine will not keep up and in 3 seconds it will shut off.

this problem interestingly only started to occur when my oem cat finally broke so i replaced with a flowmaster. i unfortunately didint have the time to repair myself so i gave it to the shop. when i got it back i immediately noticed my engine not firing up correctly and soon got a CEL telling me to change the 02 sensor bank2sen1. replaced tht with NTK but ofc didnt fix the issue.

I have no other codes showing up on my dash and im leaning towards the 02 sensors tht link to the cat or something with the transmission when it was lowered to remove the broken cat.. any thoughts? before i tune my jeep up with plugs and cleaning. again thnks for the helps guys
 

robo512

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Jan 11, 2021
Messages
45
Location
NW Indiana
Did the problem happen before the new cat was installed or only after? It sounds to me like you got the engine codes for O2 sensor and the problem running at idle after the cat was installed. That leads me to believe it is an issue with the cat
 

Jerry Bransford

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So it only dies at idle rpms? Does it feel/sound like the rpms are struggling to stay high enough and then it dies or does the engine feel like you just turned the ignition switch off?
 

Rubicon88

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Sep 24, 2020
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2,400
Location
Western PA....Altoona area to be exact.
I take it you owned this when it was running well....

You need to pay extra close attention to it.
I'm willing to bet you've got some other symptom(s) going.

Does this run OK on a cold start and only stall after it's been running and warmed up?
Does the stalling occur immediately when it's cold as well?
 
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silv1010

silv1010

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Mar 17, 2021
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3
Location
New Jersey
@robo512 no problems at all before the new cat was installed only after.. the job looks good i can take pics later this afternoon.

@Jerry Bransford it struggles for sure at low rpms and when in idle (jeep vibrates) and then turns off.. never happened to me before only after this new cat was installed. i could tell when i turn on the ignition it was quieter then usual almost as if i needed a better kick. only a few days later i got the idle issue and P0155 (so i replaced the 02 sensor) the jeep would turn off on me at the red light.

@Rubicon88 yes no problems before. the jeep will turn on just fine in any weather condition (hot or cold). its only when the engine gets warm enough (after 15mins of driving) when it starts turning off when i idle so the stalling occurs immediately when the engine is already warm enough.

i remember getting P1281 after i installed the thermostat .. meaning it was prob faulty but i didnt run into issue like stalling so didnt change it and plan to when it starts getting warmer. also may look into the battery but everything was fine before only after this cat job..
 

Jerry Bransford

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That it's struggling at low rpms could mean nothing more than a dirty/clogged IAC (idle air control) which is what provides ALL of the engine's air when it's at idle rpms.

Being dirty/clogged means it can be cleaned. Go buy an aerosol can of throttle body cleaner, then use a philips head screwdriver to remove the air intake tube from the top of the throttle body. Start the engine and keep it at idle rpms, do NOT raise the rpms up or this process won't work.

With the engine at idle rpms, spray the cleaner into the throttle body which will cause the engine to die since it is flooding the IAC. Give it 10-15 seconds to "cook" inside the IAC to start loosening up the gunk. Restart the engine and again, while the engine is at idle rpms, spray the cleaner into the throttle body again. It'll die again so after a short delay, restart it and do the above again.

I would repeat the above until you've got 1/3+ of the can through the IAC. See if it doesn't run better after doing this.

If you raise the rpms above idle to stop the engine from dying the cleaner will bypass the IAC so you won't be cleaning it. The cleaner will only get sucked through the IAC when the engine is idling. Above idle, the IAC shuts off and all of the air comes through the main part of the IAC.

One more component can cause idling problems and that's a bad TPS (throttle position sensor). But the TPS cannot be cleaned like the IAC can so if the TPS is bad it would need to be replaced. Avoid store brand TPS's, especially brands like Duralast from AutoZone. Most aftermarket parts like this are shoddily made and either won't work properly or they won't last long.
 

chotomobile

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Nov 25, 2021
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3
Location
Paraguay
Thank you for the post Mr. Bransford, although I am not the original poster I have been having the same issues, I will try what you said and update you on the results. I also have another question though, I own the 2001 TJ, 2.4 L automatic, my engine makes a rattling noise every once in a while and after having replaced the timing chain I don't know what it could be, any ideas? Thank you very much!
 
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Jerry Bransford

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I am not sure, but it could be, the noise only happens when in idle by the way.
Hmm, that doesn't sound like pinging. That's starting to remind me of the timing chain area even though I realize it has already been changed.

By the way, your engine is the 2.5L, not the 2.4L that didn't come along until 2003.
 

chotomobile

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Nov 25, 2021
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Paraguay
Sorry about that, perhaps the mechanic did a poor job. Down here getting a mechanic that can and will do his job as he's supposed to is virtually impossible without paying an exaggerated amount. Sometimes even so...