sportrider

I just got a 99 XJ, yesterday on my way home from work it lost power, started missing and poping through the intake. I've read up on this issue on here. this morning the truck ran fine, I ran a fuel pressure tesy on it and at idle it has 45psi revved up it has 49-50psi. on my scan tool the throttle sweep looks good, .8v off throttle 3.96v WOT with smooth transition. O2 sensor seems to be responding quickly. any ideas?

prerunner1982

Have you read up the Cylinder 3 misfire issue?


SUBJECT:

4.0L Rough Engine Idle After Restart Following A Hot Soak

OVERVIEW:

This bulletin involves the installation of a fuel injector insulator sleeve.

MODELS:

2000-2004 (TJ) Wrangler (Domestic and International Markets)

1999-2004 (WJ) Grand Cherokee (Domestic and International Markets)

2001-2004 (WG) Grand Cherokee (International Market)

2000-2001 (XJ) Jeep Cherokee (Domestic and International Markets)

NOTE: This bulletin applies to vehicles equipped with a 4.0L engine (sales code = ERH)

SYMPTOM/CONDITION:

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.

DIAGNOSIS:

1. 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.

18-031-03 -2-

PARTS REQUIRED:

Qty. Part No. Description

1 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.

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 (from driver's side of vehicle).

Also:

SUBJECT:

4.0L Multiple Cylinder Misfire

OVERVIEW:

This bulletin involves inspection of all engine exhaust valves and a decarbonizing

procedure if necessary.

MODELS:

1999 - 2004 (WJ) Grand Cherokee (All Markets)

2001 - 2004 (WG) Grand Cherokee (International Markets)

1999 - 2004 (TJ) Wrangler

1999 - 2001 (XJ) Cherokee

NOTE: THIS BULLETIN APPLIES TO VEHICLES EQUIPPED WITH A

4.0L ENGINE (SALES CODE = ERH).

SYMPTOM/CONDITION:

The customer may experience an incident of engine misfire during certain vehicle

operating conditons. The misfire may occur when the vehicle is operated between

80 - 112 KPH (50 - 70 MPH) and under light loading conditions, e.g. slight uphill

road grades. This condition may occur at all ambient conditions, but is more

noticeable when ambient conditons are less than 0 C (32 F).

If the vehicle is equipped with On-Board Diagnostic (OBD), a MIL illumination may also

have occurred due to Diagnostic Trouble Code (DTC) P0300 - Mulitiple Cylinder Misfire.

Various single cylinder misfire DTC's may also be present. If the frequency of misfire is

high the Powertrain Control Module (PCM) may place the engine in "Limp-In" mode.

The misfire condition may be caused by one or more engine exhaust valves that are

VTJeep

Popping thru intake- lean mixture: possibly fuel delivery issue. Start with a pressure test at rail, maybe blow out gas lines, if your up to it, drop the tank when fuel is really low and see if the pump/filter assembly looks good. Also you can check to see if there is any swag in the tank that may be obstructing fuel flow..

VTJeep

There are other, more basic things you can do before dropping the tank. Check all electrical connections from battery on. Check all sensors (IAC is usually more commonly associated with high idle issues, so it's prob fine, but if you have a good code reader that can view its specific activity, that will help). Look at the throttle body for build up. This may help determine if sea foaming the system may help. Either way, sea foam is awesome stuff. Other stuff to look at.. How is gas mileage? Any other symptoms?

sportrider

I've only owned this XJ for 2 days now so I'm not sure of fuel mileage yet as my commute is only 8 miles. no check engine light, no active or pending DTC. starts and idles fine. I figured it was running lean, thats why I checked fuel pressure and TPS and O2 readings. tonight when I get off work I'm going to drive home with my scanner connected so if it acts up I can see the data stream and try and determine the cause. I was surprised that no MIL or codes were stored as bad as it was running. it did clear up after about 2 miles of that then ran fine the rest of the way home.

VTJeep

Man, that's annoying- only 2 days.. Well, unless it's the PCM your probably going to solve this pretty cheaply. Assuming it happens again.. Ill say again that if your feeling ambitious, drop the tank and inspect it.. Crap in the tank or a bad pump/filter assembly won't trigger the CEL, usually, and would be a direct link to the manifold pop.. Idk.. This is jeeps.. I've never owned a more capable, needy vehicle! I pretty much had to stop wheeling cause its my DD and doing the WW/DD thing was getting expensive; too many new u joints, alignments and general this and that parts like steering stuff or DS replacements to keep it up.. Point is, they can be funky sometimes and give you odd issues that are sporadic, don't trip the CEL and don't impede regular driving enough to even want to deal with!

sportrider

ya I'll figure it out, this is about normal for me and a new Jeep (it's my 4th one) they ran great on the test drive, and crap out after I buy them. I guess it's why I'm always so intamate with them. normally by the time I get everything fixed, aside from knowing it like the back of my hand, I get a new one and start all over again.

sportrider

ok, here's an update from the drive home:
the XJ is running good, got my scan tool connected watching readings.
just as the truck starts to F-up I look at the O2 at the upstream is reading 1.89V,short term fuel trim is -13.48, down stream is reading .15V , TPS sweep is normal, ECT slowly climbs to 212, CPS is receiving 5v signal. the upstream sensor froze and peaked at 1.94V without any movement for about 2 minutes. then the sensor dropped to .22V and the throttle response returned to normal with the sensor swinging quickly.

looks like the XJ is getting a new upstream O2 sensor tomorrow. that should solve my drivability issues, so I can get back to more important things like lift kits and tires

tjwalker

Let us know if the new upstream sensor resolves it. Go with NTK for O2 if you can find one....

sportrider

I got the O2 sensor swapped out, in about 5 hours I'll know if it fixed it.

tetrad

Check your fuse 24 @ PDC (15A, second from the left on the top row of tiny fuses). I was having a similar issue with my '99, and the heating circuit for the O2 sensors had been melted and fused together by the exhaust. Rewired the downstream O2 and the speed sensor and Tcase switch at the Tcase. Fixed the issue. Just make sure you zip the wiring far enough away from the exhaust and driveline that it doesn't happen again.

sportrider

just got home and the O2 sensor seems to have solved the problem. it didn't miss a beat on the drive. I did notice improved throttle response and it feels more peppy. now I can start spending money on the good stuff!!!

tjwalker

Glad this is resolved. That O2 sensor is awfully important.

Now start spending money and mending our economy!

jbossnack

I've got a 1999 XJ Classic with a 4.0 and I've been chasing a problematic idle for a long time. It idles like crap. The longer it runs and warms up the crappier it runs. When cold it starts up great and runs great for about 5 seconds then you can notice the slight shakes, after it comes to full temp it really wants to crap out. I have to keep feathering the throttle or else it will sputter and want to die out on me. I've replaced so many parts I'm sure it's not a fuse or wiring issue, and pretty sure it's something controlling the fuel/air trim levels.

I replaced my O2 sensors last year with ...BOSCH O2 sensors, I know I know, I am reading that Bosch O2 sensors suck and I'm to be using NTK O2 sensors.

I'm going to try to swap back in my old O2 sensors after cleaning them up with carb cleaner and see if that makes a difference.

BUT why does everyone say Bosch O2 sensors suck for the XJ ? What's the reason?