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Discussion Starter · #1 ·
Jeep was running well then I started misfiring.

Lots of new parts in my motor, including the injectors.

With this problem my fuel pressure is rapidly bouncing between 42-53 and goes with the the sound of the engine chugging.

This vid is not mine but looks about the same.


The codes that showed are:
PO202- injector 2 control circuit
PO204- injector #4
PO301- cylinder 1 misfire
PO303- cylinder 3 misfire
PO305- cylinder 5 misfire
PO308- misfire in multi cylinders

Everything was running very well. I don't see any damages wires.

Any ideas?
 

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Discussion Starter · #2 ·
I took the fuel rail out and watched all the injectors fire ... They look really good .. All spraying fuel nicely and all look the same.

I'm running super rich or not burning off fuel well maybe. Putting out a lot of black smoke and there is a black carbon stain on the ground under the exhaust.
 

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42-53 psi is not far from the FSM specification of 49 +/- 5 psi.

You don't "see" any damaged wires, or testing/diagnosis proves without a doubt there are no faults ?

P0202 Jeep - Fuel Injector 2 Circuit Open
P0204 Jeep - Fuel Injector 4 Circuit Open

Possible causes

- Faulty fuel injector 2, 4
- Fuel Injector 2, 4 harness is open or shorted
- Fuel injector 2, 4 circuit poor electrical connection


Have you checked the running parameters with a Live Data display OBD-II trouble code reader ? What are your fuel trims, and what are the O2 sensors doing ?
 

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Discussion Starter · #4 ·
42-53 psi is not far from the FSM specification of 49 +/- 5 psi.

You don't "see" any damaged wires, or testing/diagnosis proves without a doubt there are no faults ?

P0202 Jeep - Fuel Injector 2 Circuit Open
P0204 Jeep - Fuel Injector 4 Circuit Open

Possible causes

- Faulty fuel injector 2, 4
- Fuel Injector 2, 4 harness is open or shorted
- Fuel injector 2, 4 circuit poor electrical connection

Have you checked the running parameters with a Live Data display OBD-II trouble code reader ? What are your fuel trims, and what are the O2 sensors doing ?
its not that the fuel pressure is off.. its just bouning all over the place ... like the vid i posted. it usually goes to 49 and stays steady.

I will check the wires again and test them. Is there a ground I should be checking, do you know which one it is?

Thanks for the help brother
 

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Discussion Starter · #6 ·
Check your TPS for correct function.
Check you O2 sensor(s)also.
Do you have a fuel filter? Some FI's do and some don't.
LG
The fuel filter is just the stock one in the tank.

Tested the tps just for fun and it's perfect.

O2 sensors seem good, I guess I could swap them out later if nothing else turns up.

Going back to work on the jeep now,

I'm going to swap the injectors and if no improvement rewire the fuel rail so it's all new. And if no luck change the ignition and plugs but the spark looks good as on this morning.

If that does not work ... Idk maybe ill swap the cam sensor, fuel pressure reg, and pump, and o2 sensors.
 

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Instead of throwing random new parts at an undiagnosed problem hoping you accidently fix the Jeep, maybe you should spend $7.95 at http://www.pacificcoastmanuals.com/ . Then you can follow the diagnostic procedures specified for the CEL trouble codes you have.
 

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Discussion Starter · #8 ·
Instead of throwing random new parts at an undiagnosed problem hoping you accidently fix the Jeep, maybe you should spend $7.95 at http://www.pacificcoastmanuals.com/ . Then you can follow the diagnostic procedures specified for the CEL trouble codes you have.
It said bad injector, bad wire, short, bad ground, pcm.

So I was going to swap the injectors.. Change the wires .... And go from there ...

I would not be shocked at all if it was the pcm.
 

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A faulty PCM would be the least likely cause of the symptoms and should only be considered after a thorough and complete diagnostic testing of the more common and likely causes of similar symptoms.


An OBD-II trouble code reader with live data display is also a good investment.
 

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Discussion Starter · #10 ·
A faulty PCM would be the least likely cause of the symptoms and should only be considered after a thorough and complete diagnostic testing of the more common and likely causes of similar symptoms.

An OBD-II trouble code reader with live data display is also a good investment.
I know your right ... I'll get some live data ... :cheers2:
 

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Bouncing fuel pressure is totally normal during operation. The fuel rail has no dampening (some late 1999s did, they weren't in the FSMs until 2000+) so every time an injector opens the pressure drops and every time one shuts the pressure rises. Same thing that happens when you slam shut the tap on your bathtub and the pipes in the wall make a loud bang.

Sounds like there's an issue with the wiring harness indeed. Sitting above the exhaust manifold bridging the gap between the engine and the body is a recipe for broken wires and shorts.
 
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