My 1997 TJ with a 4.0 starting running rough and the check engine light came on. I pulled the codes and I have a PO 306. Which is a misfire on cylinder 6.
Here is what I checked.
Spark....good.
Noid light check on injector wiring.....light flashes. Wiring to injector seems ok.
Full compression check on all cylinders. Each one was right about 150. The gauge seemed to climb steadily on each cylinder. I don't think there is any major engine problem.
I decided it probably has a bad injector. I changed the injector on number 6. Problem is still there.
What am I missing.....any ideas?
Code PO 306
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Jeepster2586
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Jeepster2586
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Re: Code PO 306
Also I went along the wiring for each injector removing the connector while it was running . Cylinder 6 was the only connector that made no change when unplugged. That was the reason I changed the injector.
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Kurt
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Re: Code PO 306
Possibly a wiring issue between the PCM and the injector.
If you have a meter you could check for proper continuity between the two.
If you have a meter you could check for proper continuity between the two.
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Jeepster2586
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Re: Code PO 306
The weird thing is that if I plug in the noid injector tester the light flashes which means the wiring/ pulse from the PCM is valid...I think???? I also plugged it into every other injector wire and it appears that all cylinders are receiving pulses from the PCM.
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MDSRACING398
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Re: Code PO 306
Make sure exhaust manifold didn't crack. Also cam positioning sensor can cause misfire codes. Could of got bad injector too. Can do the old swap injectors on cylinders and see if code moves to other cylinder.
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Kurt
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Re: Code PO 306
You could have a bad spark plug.
I've seen them fail causing a cylinder to cease firing even though they look "good".
Might try swapping spark plugs around and see if the problem moves cylinders.
I've seen them fail causing a cylinder to cease firing even though they look "good".
Might try swapping spark plugs around and see if the problem moves cylinders.
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Jeepster2586
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Re: Code PO 306
I replaced all the spark plugs. No change. I guess I am going to try spraying brake kleen around the intake manifold while its running to see if that changes the RPM. I will swap the injectors around and see what happens.
Can a cam sensor cause only one cylinder to misfire? What about the crank sensor? Would that do a single cylinder misfire?
Also I'm going to do a vacuum test just to rule that out.
Can a cam sensor cause only one cylinder to misfire? What about the crank sensor? Would that do a single cylinder misfire?
Also I'm going to do a vacuum test just to rule that out.