So I did use the search function...

the brief: Jeep runs great, except at stoplights where the idle seems rough. If I put it into N or P the idle is just fine

some here suggest cleaning IAC, could this be the culprit or something else?

I recently changed intake/ exhaust manifold recently and didnt remove the intake manifold completely and couldve banged the O2 sensor screwing it up.

or could this be the aftermarket CPS (installed 9 months ago) giving me hiccups

It did not have this trouble prior to redoing the manifold gasket

Thanks guys

 

Did you make sure you torqued down the manifold correctly? You may have a vacuum leak. You should take out the IAC and soak it in carb cleaner and scrub it with an old toothbrush. You should change out the upstream o2 as well. Throw in an NTK sensor. Look into rockauto.com for the best price you'll find on them. You may even see a small boost in MPGs too with replacing that

 

Dbl checked the torque on the bolts once done.

Im gonna pull and clean IAC tommorow.

It could be a vacuum leak from some hose that was aggravated by me taking it off and replacing it. Afterall, everything is pretty old under the hood, but Im thinking some sensor cuz of the whole "It only does this in Drive" thing. Otherwise a vacuum should be a constant issue... right?

 

only in drive? sounds like a torque converter issue.

 

If you were disconnecting and moving around old brittle hoses, you very well may have accidentally put a crack in one somewhere. That would also be good to check. The way I see it, if you're in park and you are idling, you aren't getting air flow to that vacuum leak that you would be getting if you were moving. But I don't know because I have never dealt with a vacuum leak.

Also, did you remove the fuel rail and injectors when doing the manifold? Did you ensure you hooked them back up correctly with the plugs going to the corresponding injectors?

 

Hope you find the cause.....i'm having the same exact issue (prob vacuum leak, which is a pain to find).
Pls update.

Thx.

 

I have a 98 and mine would try to take off when I had my foot on the break sometimes at red lights, turned out to be the TPS.

 

well its not the IAC. took out and cleaned today. It might have improved things slightly, but its hard to tell as the idle stumble seems to be aggravated with hotter weather.

I've been listening for vacuum leaks when I did the manifold gasket and did the PCV at the same time. No hissing to be heard

gonna try the AIR TEMP sensor and the upstream 02 sensor and see what happens. air temp is cheap enough and 02 is long over due for replacement

 

Both the IAC and HO2S1 would throw a code if not functioning properly and would cause problems under all conditions. Unless you like throwing parts at it, so be it.

But as far as running rough at idle could you describe it more? Does it seem like a missfire? Loping idle? Or seem as if its under load?

 

Had a rough idle as well put better gas in it and seafoamed and it smoothed it out quite a bit. Not completely though.

 

step 1 check for codes even if lights not on

 

FRANKLIN. the idle seems to be a tripping or stumbling. the RPM range is 550-750... when its not doing it its pretty stable around 700. Id call it a miss but im a little fuzzy on definitions. It is not smoothly oscillating between 550-750, theres an oddness to it which makes me say "miss", whereas smooth is "loping"


freegdr... would love to check for codes but GOD bless California which wont let AUTOZONE and the likes loan out computers, only service centers BY LAW can scan for codes

Ive done seafoam a plenty, its no miracle cure

 

I take it back, it has the same problem in P or N, its just much less noticeable and less frequent at the 950 rpms it idles at.

it also seems to not have a problem (though I gotta goof around with it a bit more) if I put my foot on the brake gently give it a little gas and have it sit at around 1000 rpms.

Im gonna get out the camera and video the thing a post it tomorrow

 

I recently put new freeze plugs and a manifold gasket on mine and when I put it all back together, I had vacuum lines hooked up wrong. I'd double check that they are hooked back up in the right places if you have a vacuum diagram.

 

Well wouldn't you know, as soon as I try to record the problem its diminished to such a point that I can't get a good video/audio showing the problem.

will post back when I figure something out