My 08 recently started to get a rough idle at traffic lights, drive through and mexico border wait of 30 minutes can really cause it to "putter." It was happening for a few weeks. I replaced spark plugs 3 days ago and its either still the same or possibly even worse.

It does it in all gears but I do feel a big shake going from Park to Reverse. I have experienced this with the torque converter and it was replaced by dealer 20k ago but of course the mechanics are the worst there. I don't think its the transmission (could be a separate problem) since it will also putter and shake in park.

It's been 180k so I'm sure I am due for a new sensor if that could be causing it. Throttle body is clean as can be, plugs and wires and coil pack are new. No check engine lights. My guesses are fuel injector slightly clogged, vacuum leak, bad fuel, bad sensor maybe MAP, or torque converter again....

Thanks in advance for the help.

 

Vacuum leaks are what always comes to mind first when I think of rough idles. And they're always so damn hard to pinpoint as well . If you're not throwing a code, that would be what I think is the most likely cause.

 

I had my EGR bolts come losloose and that caused a vacuum leak that was presenting like a throttle body, but it was enough air to about kill all power when it heated up. Just another place to check since you've knocked off the usual suspects. Did you ever get your PCV straightened out?

 

Can vacuum leaks be intermittent? It only happens a few times a week and not constantly. Other than the farting and puttering in the drive through or stop light its as smooth as can be. The issue happens in all gears including park.

 

OK i can check there for sure. Yea I didn't want to take apart the throttle body just yet because I had a conversation on here with the usual players but still cant figure out if my 08 has a certain type of gasket. There are 3 choices and I haven;t checked if the other is available locally like a felpro in case its the wrong one. I'd order the mopar again there just could be a few diferent options for my 08 so I'll start there.

The PCV valve i cleaned up the valve cover of oil all around the PCV hose and I have not had the oil spill as of yet. I am only at 2k since I wiped it down so I will report back on that.

I also will let everyone know how I am liking the new KM3 tires shortly (hint amazing!) in a post the waves in So cal and Baja have been on a run so I've just been logging the miles as of right now.

 

 

You go to Mexico a lot, so bad fuel is what comes to mind first. But it's been decades since I was there, so maybe it's not as much of an issue nowadays. Some good fuel system cleaner is a potential cheap fix.

A really hard to diagnose rough idle can be from an EGR valve that's not closing completely, often from a bit of carbon on the plug/seat of the EGR valve. It might fix itself with continued driving highway miles. Another symptom of this type of fault is that it runs good, except for a rough idle. It also might come and go, or just vary depending on how much is leaking by the closed valve -- Not much different than how a leaking faucet behaves.

Timing chain wear can produce a bad idle, but there would also be telltale noise, so that's probably not it. And you've likely ruled out the plugs/coil. A decent vacuum leak will make a high idle and set a code, but small leaks (meaning constant rather than rapidly varying) won't make it rough (on a speed density setup like the JK).

 

Ok so back down to Baja for this swell and I figure if I'm putting 180 miles on it straight to run a can of sea foam. I checked around a bit and can't see anything out of place or simple like the air box hose disconnected.

Sea foam but still rough idle. Where are common vacuum on this besides the EGR. The only hoses I know of are the Brake booster and air box? I'm sure there are a few more but this is new issue I haven't had to deal with yet.

 

For some reason it felt as if the star bolts on my throttle body were lose. I opened the butterfly and saw a small piece of the gasket sticking out. Can anyone identify if this is considered flush mount or recessed lip? I want to pull it apart and change the gasket but for my 08 there are two choices. I posted about this a while back but I never got anyone who really knew the answer.
Here is hopefully some better pics for reference.

 

That looks like some silicone sealer that someone added, which would be a mistake unless the surface is damaged and silicone is a last resort. Seen that done before, makes it hard to take apart. Be careful removing it, maybe it's just some misguided techs idea.

The gasket on my '08 is a lite-blue O-ring with some ribs on it to hold it in place during assembly. Just looked it up, Mopar 4666113AA. Yours could be different, but I'd put odds on this one.