zone zero

I'll try to keep it short. 2001 cherokee 4.0. Replaced the engin with a new crate 4.0 around 1 year ago. At. The time I replaced all the injectors ,altinator, starter water pump, all the sensors, and your typical stuff when taking the time to do this kind of project,

For the last 5-6 months when the engins up to temp it runs fine until I shut it off. If I come back out from a store or from the house the jeep will not start. Until the temp is well below 210. One way I can get it going is to hold the peddle to the floor and crank it over it will fire up but run hard misfire and until it smooths out there's almost no power.

I've had it plugged into the Obd-2 computer check at the shop and it throws no code never throws a check engin light on the dash.
I'm lost where to look next, I was thinking of taking it to the dealership but I've had 11-12 jeeps over the last 15 years so I think I can fix this if I knew where to look.

RTorrez1

I would start with the basics. Make sure that you have a good bright blue spark. Also make sure that you have the correct fuel pressure. Check it at the fuel rail with a mechanical pressure gauge. Your 01 should have 49psi + or - 5psi and it should hold the pressure with in that range also. Check those things out first then we can go from there.

SeriousOffroad

Do a search for HEAT SOAK.

salad

+1 this is heat soak typical of 2000+ 4.0Ls. The extra catalytic converters in the exhaust manifold throw off so much heat that once you kill the engine (fan) the fuel in the injectors boils. Chrysler issued a TSB acknowledging this problem.

The fix is to insulate the fuel injectors and rail with heat wrap. It's an adhesive foil product. I recommend wrapping all of the intake and fuel stuff in the area.

EdZ

I'm thinking a leaking injector(s)... If you were to pressure test the fuel rail then run the engine for a bit... Shut it down and wait 10 minutes or so... Check the pressure gauge to see if it has lost all pressure... Cycle the key (on for 5 seconds, off, then on for 5 seconds) and watch for the pressure to return... If it does, then try to start the engine again... If you still get the flooded engine symptom then it likely is one or more of your (new) injectors is bad... Hopefully you keep your old ones and for the price of new O-rings can put them back in... Clean em off good with throttle body cleaner first though... You'll likely find your problem is now gone...
I have found a good many aftermarket (cheap) injectors to fail within the first year of use... Most OEM ones are quite good and should last the life of the engine (barring abuse or lack of maintenance - injector cleaner once or twice a year)...

skife

i'll 3rd the heat soak issue, my 00 xj is great running around through the woods at low speeds, i shut the jeep off while we take a break, fire it back up and runs like garbage for about 30 seconds..

EdZ

Ya know, after reading post #4 again I can see where that might be the issue (heat soak)... But isn't it rather odd that this issue failed to show up until so late in the vehicles life ??? Also , I had replaced the cat on mine within a year of it being a new vehicle... so that maybe why I very had this issue... Much better performance from a good aftermarket one... Ya pay a price in added exhaust noise, but it is very tolerable and well worth the performance improvement...

salad

Nope... once the mini-cats have a few miles on 'em they get dirty and retain a lot more heat. Here's the original TSB:

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


That's the difference. 2001 doesn't have "a cat".

This picture is looking upwards into the engine bay. Intake manifold, upstream O2 sensors, and mini-cats are pictured:



Those are very expensive to replace

zone zero

I had thought it was a heat soak issue, so I replaced the injectors maybe 2 months ago, I got a set of 4 port injectors from a member on here. That was a big improvement. At the time I also added muffler shielding from the manifold to the cat, and insulated the injecorts and fuel rail with heavy duty race quality heat shielding. I also had the fuel pressure checked out and it was GTG. on other thing with this that has me puzzled is my fuel mileage plummeted I was averaging 15-16 mpg now I'm getting 6-8 if I'm lucky. the jeeps light weight front skid only hitch with a 3 inch lift and 255/85/16 maxis bighorns on Liberity aluminum rims they weigh nothing.
I have a 19 gal tank non abs with an 8.25 rear and 3.07 gears

zone zero

I should mention too it's been cold in New Hampshire this week, today it was below freezing all day and it was still acting up on me. I just re-read the post and there was mention that 01 only had the 2 mini cats, I have those and a cat further down the line in front of the t case crossmember.

Should I consider. Shielding the electrical on the O.2 sensors and the fuel rail?
The only other modification I did not mention was an ARB snorkel

freegdr

Does 2001 have that stupid heat shield under the injectors .

zone zero

Mine did on the old engine so I added upgraded the shielding on the new one.
I hope I can resolve this im saving some money for 456 gears and a rear locker for the spring I don't want this issue to eat up more money than it has too.

freegdr

Just found this ....http://bleepmicro.livejournal.com/57852.html

freegdr

Is this thing on tap tap tap...

freegdr

Guess not....