Intermittent rough idle

[RedBastardTJ]

Looking for some help/insight as I couldn’t find a thread about this particular issue. I have a 2005 RME TJ, 137k miles, 4.0L, auto. When I start it and it warms up it idles smooth as butter for about 4-5 seconds, then it idles rough enough to feel the vibrations through the steering wheel for 4-5 seconds and repeats. It’s not throwing any codes. I’ve changed the spark plugs, they’re at correct gap. I cleaned the throttle body and IAC. I was planning on changing the O2 sensors next. Any advice/probable solutions would be greatly appreciated. Thanks in advance

 

[Wayne Mathson]

Looking for some help/insight as I couldn’t find a thread about this particular issue. I have a 2005 RME TJ, 137k miles, 4.0L, auto. When I start it and it warms up it idles smooth as butter for about 4-5 seconds, then it idles rough enough to feel the vibrations through the steering wheel for 4-5 seconds and repeats. It’s not throwing any codes. I’ve changed the spark plugs, they’re at correct gap. I cleaned the throttle body and IAC. I was planning on changing the O2 sensors next. Any advice/probable solutions would be greatly appreciated. Thanks in advance

I have been going through the same issues this past summer with my '04 LJ 4.0 with 166K. It would idle fine at start up then once warm would vibrate like it was missing. Searched on this forum and found the thread about the throttle body and IAC cleaning. I did the cleaning and it made a big difference in initial startup and running till it was warm. But after turning off the engine and while still warm, it would start okay but then would have the rough idle again. Searching this forum again and along with YouTube, I found the subject of replacing the CPS (crankshaft position sensor), which I have done and my rough idle has seemed to disappear. It was a $30 part and easy to replace on my LJ, so it was worth it after so many miles. I still get an occasional CEL for a misfire on cylinder 1 but is usually when the weather is hot (even here in ND where it will be near 100 in acouple days). I have installed a heat soak kit and has helped immensely. Info I gleaned from a YouTube video was to disconnect both positive and negative cables from the battery when changing the sensors and to touch the cables together (or use a jumper wire clips) to discharge a stray voltage in the system (even turn the headlight switch on). Accomplished those tasks and my LJ has been running and sounding much better. Even though I had cleaned the IAC, I learned that sensor may still not be functioning properly due the solenoid being weak. So since changing it was easy to do, I went ahead with replacing it also. The coolant temp sensor, I learned too, also has a play in the issue. I had radiator problems so had installed all new items for the cooling system. Hope what I have done to my LJ might help you out with yours. Had to do research to determine what 'RME' meant. Not familiar with all the different packages that Jeep sold over the years.
Owned a '50 CJ3A back in the '70's and early '80's and now my LJ since '09. Will hang on to this till I can't crawl in it anymore.