Rapid heat

[aidanm]

Hi all,
On my 02 4.0 TJ whenever I start it when it’s cold it’ll start at a normal rpm range but as soon as the rpm starts to go down it starts to bog, almost like it’s trying to heat up too fast and causes a miss, then whenever I hot start it it starts missing again until I start driving, basically whenever I’m sitting idling is when it starts missing, wondering if anybody had any thoughts on this? I’m thinking maybe the IAC? I replaced it a few months ago but I could have gotten a dud. Also I have a 62mm bbk throttle body that’s been on the motor for probably 2 years that does the typical whistle so I’m wondering if maybe this could have something to do with it? Could a valve issue cause this? Thanks!

 

[NashvilleTJ]

Hi all,
On my 02 4.0 TJ whenever I start it when it’s cold it’ll start at a normal rpm range but as soon as the rpm starts to go down it starts to bog, almost like it’s trying to heat up too fast and causes a miss, then whenever I hot start it it starts missing again until I start driving, basically whenever I’m sitting idling is when it starts missing, wondering if anybody had any thoughts on this? I’m thinking maybe the IAC? I replaced it a few months ago but I could have gotten a dud. Also I have a 62mm bbk throttle body that’s been on the motor for probably 2 years that does the typical whistle so I’m wondering if maybe this could have something to do with it? Could a valve issue cause this? Thanks!

Did this behavior start when you added the throttle body? Was it doing it before you replaced the IAC?

 

[aidanm]

Did this behavior start when you added the throttle body? Was it doing it before you replaced the IAC?

I recently replaced the motor because it was ticking pretty bad with another motor, this newer one was from another 02 but an automatic, this behavior has been happening ever since I put the motor in, but I’ve done all the tests on the motor like a leak down tester and compression test and they both came back good.