2000 XJ #3 Cyl. Misfire

Pless

Pless

Well-Known Member
Joined
Jul 26, 2006
Location
Canton NC
This is a buddy of mines XJ. Its a 2000 Sport with a 4.0 and an auto tranny.

About a month ago it started missing. At first it wasn't bad just every once in a while. It started getting worse and started smelling like it was running rich a couple of weeks ago. It threw a code for #3 cylinder misfire.

With the fact that it was running rich we assumed that the injector might be stuck open so we replaced that injector. It didn't change anything.

Next we took a stethoscope and started listening to each injector. All of them had a steady sound to the except for #3 it was sporatic.

Annother buddy of mine thought it might be the ECU. So we came across an ECU cheap and we swapped it out. Still no change.

After that we thought it might be the crankshaft position sensor so we swapped it out and still no change.

I had a camshaft position sensor at home and we swapped it in still no change.

I have thought about the coil packs and plugs, but if it were them, it dosen't explain the sporadic way the injector is firing. It was running so rich at one point it was actually blowing raw fuel out the exhaust. We are at about the end of our rope on this one if anyone has any ideas I would appreciate the help.
 
Is it code P0303? I got this from alldatadiy.com for a 2000 TJ with the 4.0:
SYMPTOM
P0303 - CYLINDER # 3 MISFIRE

TEST NOTE
This symptom is diagnosed using the test P0300 - MULTIPLE CYLINDER MISFIRE.

WHEN MONITORED
With the engine running, after successfully performing a crank sensor learn.

SET CONDITION
When more than a 2 % misfire rate is measured during two trips, or with a 10 % to 30 % misfire rate during one trip.

POSSIBLE CAUSES

* Misfire intermittent
* Other possible causes for misfire
* Cam, crank, valve timing, or vacuum problem
* Ignition coil output low
* Engine mechanical problem
* Secondary ignition pattern irregular
* Fuel contamination
* Fuel pressure leak down out of specification
* Fuel pump amperage out of specification
* Fuel pump capacity out of specification
* Fuel pump pressure out of specification
 
redman_30_06 said:
That is the code.
He also just told me that it is throwing a
P203 Injector Circuit/Open - Cylinder #3
Click to expand...
from alldata:
SYMPTOM
P0203 - INJECTOR # 3 CONTROL CIRCUIT

WHEN MONITORED
With battery voltage greater than 10.4 volts , the Auto Shut Down relay energized, injector pulse width less than 10 ms , and engine speed less than 3000 rpm .

SET CONDITION
This DTC takes 0.64 to 10.0 seconds to set when no inductive kick is sensed, 18 ms after injector turns OFF, and with no other injectors ON.

POSSIBLE CAUSES

* ASD relay output circuit open
* Injector # 3
* Injector # 3 driver circuit open
* Injector # 3 driver circuit shorted to ground
* Injector control circuit wiring harness intermittent defect
* Injector control circuit wiring harness observable defect
* Powertrain Control Module
 
I appreciate the full description of the codes.

At this point all I can guess is something in the harness or one of the pins in the plug.
 
i know this sounds crazy but it could be the fuel pump, had a problem just like that with my tj. keep getting that rich fuel mixture and the code was saying cylinder misfire...i changed all kinds of stuff before i found out that was the problem. i read about it on some forum but ui cant remember where.
 
BallsDeepJeep said:
i know this sounds crazy but it could be the fuel pump, had a problem just like that with my tj. keep getting that rich fuel mixture and the code was saying cylinder misfire...i changed all kinds of stuff before i found out that was the problem. i read about it on some forum but ui cant remember where.
Click to expand...
Doesn't sound crazy, P0303 has the pump listed as some of the causes.
* Fuel pump amperage out of specification
* Fuel pump capacity out of specification
* Fuel pump pressure out of specification
 
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