Idle problem after cooling

So I have been chasing this for a while with no luck...hoping maybe someone has been a similar problem and can give some new direction.

2000 Cherokee Sport, AW4, 231tc, 140,000 miles, Cali emissions vehicle.

You can drive the XJ all day with no problem, but when you get the motor hot to operating temp and then shut it down, it will idle rough upon startup if you try to restart within 10 minutes. If you open the hood, this does not happen: It will run fine as if nothing it wrong.

When the rough idle starts, if you gas the jeep to 2500rpms+ and hold it, it will clean out and run fine after a couple seconds. If you let the rough idle continue, it will flash the "Catastrophic Catalytic Converter Failure" code and then throw a couple misfire codes.

I have replaced the O2 sensors (w/ cali ones), the CPS, the entire front section of exhaust from the manifold to the tailpipe, the plugs have been changed, air filter is clean, and the coil pack has been replaced. Not entirely sure where to go from here.

Maybe I am missing something simple, or maybe not...any ideas?

search on "heat soak"

there was a TSB concerning injector #3 (IIRC) suffering from heat soak-- the solution was a thermal sleeve to reflect/ insulate it from high ambient temps.

Heat soak.

The TSB is a joke.

Install a timer to the efan so it will run for 3-5 minutes after engine shutdown.

Timer: http://www.at-fairfax.com/P1786-ELK-960.htm

You should do a write-up on installing a timer like that in a late model. Any modification of the stock fan control circuit throws a CEL on mine, and for the average guy trying to figure out what heat soak is, adding electronic controls might be a bit daunting.

Done the injector sleeve, didnt work. I work in a big rig shop, I can figure out the wiring and stuff no problem. Ill give that a shot and see what comes up.

Hallo. Is in your Jeep from 2000 still an ignition coil? You have changed the coil pack? Is this the same?
If hot (even after 10 min) it can give start problems..
'92XJwim

My 2001 has had this common problem for years. I tried insulating the injectors and a few other ‘fixes’ but nothing really worked until when, two years ago, I installed a timer to run the electric cooling fan 2-3 minutes after the engine is turned off.
It only needs to be used on hot days when the engine will be restarted within 10-20 minutes. I installed push button on the console that activated it. It gets used a lot while off-roading, especially after long, slow, hard climbs on warm days
Most of the details are in my photos below.
Fan timer
http://www.flickr.com/photos/lwade/sets/72157617434915718/
http://www.at-fairfax.com/search-results.php?keywords=Elk-960&submit=Go

This last summer, I installed a cowl intake, which lowered the intake temperatures significantly, and it helped a lot. I suspect that hood vents would also be of great help.
Cowl intake
[FONT=&quot]http://www.flickr.com/photos/lwade/sets/72157622703531169/ [/FONT]

Thanks for adding your experience with this setup. It looks like you did it right. Other people have problems with the check engine light on the newer models. I take it that this did not happen to you? Where did you connect in?

I wired in a fan override switch without a timer on my 01. I got myself in the habit of leaving the fan running whenever I stop and know I will be leaving again within 10-20 minutes. Works like a charm, no problems with the CEL.

[FONT=&quot]

winterbeater said:

Thanks for adding your experience with this setup. It looks like you did it right. Other people have problems with the check engine light on the newer models. I take it that this did not happen to you? Where did you connect in?

Click to expand...

I too was having the problem of the poor idle and CEL coming on after a hot restart. The fan setup, when used, eliminates the vapor lock like symptoms.

I connected the timer to a continuously hot source of 12-volt power, adding a 5-amp inline fuse. The timer's output goes to the trigger terminal of a 40-amp relay that was previously installed for a fan bypass switch.
I had to add a diode to prevent back feeding of power through the fan bypass switch into the ignition. [/FONT]