Rough Idle....Only When Warm??

Ok,

First, yes I did search, but to no avail.

Bunch of rough idle threads but none this specifc.

2000 Cherokee Classic 4x4 127k miles. Stock engine/drivetrain

Just replaced plugs about 2k miles ago.

A few days ago it started acting up by surging/rough idling but only after starting up again after I shut it off when the engine is warm.

I find this strange that it's only started doing this when the outside temp has been on the warmer side lately (60 degrees).

Any thoughts on this one??

TIA

cyl 3 misfire due to heat soak, google it
the jeep dealer has a little silicone bootie to insulate your injector
that being said, any one use the dealer item fix how well did it work?
i'm having the same issue
eta just saw your user name see post below

more info in 2000 they redesigned the exaust to use two pre cat converter this causes a heat soak issue warming the intake enuff to vaporise the fuel in the injectors mainly #3 after about 30 sec the vapor is blown through and your engine should run normaly sound bout right?

I actually just found a thread on "heat soak" after digging a bit deeper withing the forums... seems like a pretty annoying issue, but nothing that could cause real harm I suppose...

So if I take it to my dealership and tell them about this known issue, is there anything they can do to help?

Or is my only other option getting a timer of sorts installed in my efan to cool down the engine after shutoff?

Thanks again folks

You can try installing the TSB yourself (very simple to install) but be aware that not all people have experienced a great fix with it. As they say, "your results may vary". The fan option has been done by more than a few, you probably found a thread on that?

TSB
1803103 - 4.0L ROUGH ENGINE IDLE AFTER RESTART FOLLOWING A HOT SOAK
Date: 09/05/03 (supercedes 1802702 dated 09/06/02)
Model Year(s): 1999-2004

Description: NOTE: This bulletin applies to vehicles equipped with a 4.0L engine. This bulletin involves the installation of a fuel injector insulator sleeve.

Details: Customers may describe a 20 to 30 second rough idle following the restart of a heat soaked engine. This condition may be most noticeable when the engine is restarted following a prior 10 to 20 minute heat soak in hot ambient conditions of approximately 32 C (90ºF) or higher. This condition may be consistent with short city stop-and-go driving trips and can be aggravated by the use of fuel with a high ethanol content. Depending upon various conditions a MIL may occur due to DTC P0303 - Cylinder #3 Misfire.

This condition may be caused by heat from the exhaust manifold that following engine shut down migrates to the area around injector #3 and causes fuel vapor to form within the injector. This in turn may cause a momentary misfire of cylinder #3 until the fuel vapor is cleared of injector #3. The insulator sleeve lowers the injector #3 temperature to a point below which the fuel will not normally vaporize.

If vehicle exhibits a rough idle, and if a misfire of cylinder #3 is observed following a 10 to 20 minute hot soak, perform the Repair Procedure.

Parts required:
56028371AA Ignition Wire Shield

Repair procedure:
1. Cut insulator sleeve, p/n 56028371AA, to make two (2) insulator sleeves about 25-30 mm (1 in.) in length. See diagram.
2. Install one sleeve around injector #3, with the slit on the upward facing side of the injector. Install the other sleeve with the slit on the downward facing side of the injector.
3. Confirm sleeve is flush to intake manifold surface around injector.
4. Check injector #3 wire and ensure that the injector is rotated to a 2 o'clock position.


TSB for the cold start rough idle and P0303 code: TSB 18-010-01

I picked up one of these insulators form the local Jeep dealership and it was a total waste of 8 bucks. It still has the rough idle after a hot soak. I havent had time to come up with something better but Im thinking about it. If I were you I wouldnt buy the crappy Jeep part.

Mod: Removal or modification of federally mandated emissions equipment is highly illegal, in ALL 50 states. Unless you like getting reamed, don't post about it!


I read about this all to much on what should be the MOST reliable xjs!

Right? The last shoulda been the BEST!!!!????????

96XJ_4.0 said:

Mod: Removal or modification of federally mandated emissions equipment is highly illegal, in ALL 50 states. Unless you like getting reamed, don't post about it!

I read about this all to much on what should be the MOST reliable xjs!

Right? The last shoulda been the BEST!!!!????????

Click to expand...

NO! :twak: :twak: :twak: :twak: :twak: :twak: :twak: :twak:

That is illegal.

Discussing it on the Forum is going to get you into trouble.

OP, not all vehicles covered by the TSB and suffering heat soak have the mini-CAT system, that is only on the vehicles with the 50 state emissions package--you can check your sticker under the hood or look at the exhaust system.

Best results have been reported with using a timer, here is a link to a LONG thread where a forum member tried about everything without success and is now installing a timer--read the whole thread and make your decision: http://naxja.org/forum/showthread.php?t=1009745

I think a timer on the fan would be cheaper than replacing, Headers, PCM, cat, exhaust, and might as well replasae O2 sensors since everything else is new.

Hood vents are also a great option.

Google header wrap. Find the smaller 1"x15' roll thats around $9 and use it to wrap the entire fuel rail and injectors. Problem solved.

On my 2000XJ I only used a leftover piece to wrap #3 injector and the problem is gone.

Looking at the layout of the exhaust I am going to do #4 soon because as was mentioned the pre-converters push a ton of heat out into the intake and injectors.

This is definately a good thread to have floating around, mine had all the appropriate heat shielding but it was ratty and swollen so I tore it out. First trip up 7-UP at Brown's caused it to manifest itself after fighting all the snow collected heading up the lower trail up. Needless to say I repurchased the injector fix and the debris shield to fix the heat soak. I went one step further and wrapped the injector sleeve with aluminum tape to reflect more heat. No problems since!

On the 2000 & 01 ones can we swap out the exhaust to 98 type where the catalyst is not in the engine bay and its under the jeep ? Will that help me out with heat soak on my 2001 ? I know it will cost some $$ but can it Help ? After all is than not the problem anyway.

Removal or modification of federally mandated emissions equipment is highly illegal, in ALL 50 states. Unless you like getting reamed, don't post about it!Just don't do it!

__________________

But the 98 XJ exhaust system past the Federal laws,.. But not if I move it onto a 2001 ?

What if a just move my two cats down and out from under my engine bay?

Yes I like the timer. And may end up doing that. I did remove the rubber strip on the back of the hood long ago.
Thinking of adding in about 1/2" spacer between the back hood brackets

You could move the cats but you would have to relocate all four of the 02 sensors as well and still have space for the third cat underneath. Vehicles are subject to the regulations in effect at the time of manufacturing so even though a 98 is legal on a 98 it would not be on a 2001. Are you throwing any codes at all?

1998 exhaust onto 2001 = Nevermind,...
I have 3 cats on the 2001 ! Never notest that,.
However I do wish to upgrade the exhaust manifold anyway.
moving 4 O2 sensors dose not sound to hard.
throwing codes. Yes all the time,. Dam you 10% ethanol

If you crawl underneath the third cat should be right before the flange that connects to the rest of the exhaust. If you attempt this definitely take pics. A lot must have to do with the ambient temperatures as a cold winter after my fix worked I'll have to see how summer treats it, Oregon also has the 10% Ethanol :explosionDoes it make sense to add something to fuel which causes corn shortages and price increases, decreased gas mileage, more fill ups along with gas prices going up even though they are cutting it with another product? Somebody is making some bucks.

So one could get headers and use the 3rd cat for the O2 sensors. I guess youd have to weld 2 bungs before and after the 3rd cat to make sure the O2 are reading properly.