I have a 96 4.0 auto 4x4 175xxxmi. I have already done a full tune up and cleaned throttle body. Problem: when ever im in gear stoped it starts to idle rough and the whole jeep shakes kinda bad and it only gets worse the longer im stopped the rpm sits around 600-500. But when I start to drive again it smoothes out. But I will have some serious power loss if I have sat for to long. I have cleaned the IAC but it doesn't seem to be the problem. Also no codes are are being tripped. Anyone have any ideas or have the same problem?

 

Could be one or a combination of things. You may have a bad exhaust leak. You may need a new o2 sensor. You may need to run some Seafoam

 

It did have an exhaust leak but i replaced the cracked header from the PO and fixed that. And I ran some seafoam through a couple months ago. Wouldn't a bad 02 sensor trip a code?

 

Not necessarily. They can get "lazy" and cause a rough idle and a small decrease in MPGs without causing a CEL (check engine light).

 

Oh alright cool. Would it most likely be the upstream 02 sensor then?
Thanks for your help

 

That's correct! Check out rockauto.com. They have the best price I've seen for the brand o2 that came from the factory (NTK). I'd suggest doing that.

 

just yesterday I found the 3 wire sensor that is in the distributor on my 99 .....where it goes into the dist body had all 3 wires exposed. Very hard to see until I pulled it out. I changed that and it took away my rough Idle that has been a problem since I rebuilt......now runs great

 

Alright thanks ill look into that

 

Alright ill check that out thanks

 

The camshaft position sensor is a possibility. But not as likely of a cause as the upstream o2. And it's definitely more expensive. So the o2 sensor is a better place to start. Besides, it'd be good to replace it anyways and you may even see an extra MPG or two out of it.

 

Alright thanks for all the help.