Troth

2001 Jeep Cherokee Sport 4.0 L I 6.

So this has been happening for about 6 mo. When the jeep is warm (like everything is up to temp and has been for a while) and I restart it, it starts very rough. it has a very rough idle, almost feeling as if the timing was jacked. but then I put it in drive and take off into a very smooth idle and normal operation. there are no other symptoms after I roll away from the parking spot. I could drive for 3 hours with no issue. its just when am restarting the engine after a long drive (warm car).
today, I had the same situation as I had been having, but this one was way worse, and almost died. I almost couldn't take off out of the rough idle. then I did and everything fine. now I'm home and worried.
could this be due to toasted O2 sensors? They are probably stock from 2001. I never had any O2 issues with my old 92'. I do notice that there is also an O2 sensor in the exhaust header (unlike my 92'")
So...
What would be symptoms of O2 sensor failure?
Does it sound like this is the issue?
What else could be related?

in my rationale, the O2 sensors are incorrectly reading the remaining exhaust vapors (due to temp?). this is causing the computer to alter the fuel/air ratios and leading to a rough idle? I dont know how driving out of it works, but not reving out of it. it seems to be inked to forward movement.

Thanks Guys!

Troth

https://www.cherokeeforum.com/f2/los...r-head-180803/


I hope that it is not a head issue...

RTorrez1

First start by checking it for any stored codes. Then go from there.

Troth

stored codes even if its not throwing any? is that something that napa could check out?

EZEARL

I reckon NAPA does it. If they do they should be able to check for codes,test your battery,starter,alternator, and charging system. I had all that done on mine at Advance Auto when I was having low idle issues.

salad

Check codes.

There is a well known heat-soak issue on 2000 and 2001 models. Fuel in the injectors boils due to heat from the exhaust manifold after you shut the engine off. The Chrysler TSB issues a heat wrap around the injectors. IIRC they will perform this fix for free, or you can pick up some heat wrap and insulate the injectors yourself. If you go that route I suggest wrapping everything above the exhaust manifold. (intake manifold, injectors, fuel rail, fuel line)

Troth

ok, thanks guys. is there more info or links on that heat issue?

Troth

any literature on this?

RTorrez1

Yes, Any parts store can run it for any stored codes for free. And yes it can still have some codes even without the CEL coming on.

salad

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

Troth

Mr. Salad Man. Thanks for the info. it sounds just like my issue. do you think that I should upgrade the injector rail, while simultaneously insulating the system? also, does this issue cause long term damage to the engine? heard the loudest knock today :-(

jakecarder

My 2000 suffers from heat soak issue as well. When its over 90 degrees outside is when its the worse. I have even wrapped my injectors in off the shelf Autozone shiny insulated heat wrap. It works but when its really hot outside it don't at all. My buddy that has a 98 with no precats at all, the precats on our 00 and 01 is what the excess heat comes from, had the the same problem and paid the dealer 150 dollars to install the insulators on the injectors and it worked well for him. They seriously are junk tho and would not go that route. Its like cardboard and is held on with zip ties. What I have found to be proven to work for me is parking in a shaded are and just pulling the release cable on the hood so all the heat can escape. When I start my build and motor replacement, my jeep will receive some hood vents. There's quite a few ways to do it from factory junkyard finds, home heat/ac floor registers, 50-150 online hood vents to 400$ aftermarket vented hoods.

salad

Aren't any upgrades to the injector rail, just wrap everything with insulation. Also make sure the cooling system is up to snuff so that heat moves through the engine properly, your O2 sensors and tune-up hardware are fresh, and vaccuum system is not leaking so that you aren't running lean. Hood vents aren't a bad idea if that's your thing, tons of threads here on how to do them properly, however I certainly wouldn't skip the other steps.

Troth

awesome!! I installed a chrysler Labaron hood vent on my old 92. I built a drip pan for it because I live in or and I didnt want any moisture on my electronics/engine. Last time it was on the passenger side above the distributor. in the summer (when I lived in Boise) I would take the drip pan out, you could stand back after parking it and see the heat waves pour out of the hood. perhaps I should try to find another big vent like that and install it over the PRECAT EXHAUST MANIFOLD? (is that the silver massive header by the injectors before the normal ~6 tube system)

hood vents and injector insulation?

Troth

https://www.cherokeeforum.com/f59/chrysler-lebaron-hood-vents-65170/

my posts are on the bottom of the forum page and final photo on 2nd page