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Slightly low fuel pressure

GoBig06

NAXJA Forum User
I have a 1999 4.0L xj that I currently replaced the catalytic converter and up/downstream O2 sensors. I was driving on the highway to get my cat hot for the emissions test and I got a P0300 random missfire code. I replaced all the spark plugs and wires then I tested the fuel pressure and got 44-45 PSI. Which is slightly low from the 49 PSI I should be getting. Is this a cause for concern or should I be chasing issues else where?
 
I think the fuel pressure is fine. I would look at #1 plug wire or maybe all plug wires.Start it at dark night and look for any sparks from wires. Also check the rotor cap and rotor.
 
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Bosch O2 sensors or NTK ? Rebooted the PCM after the install ?
 
Bosch 13138 and 13399 (upstream and downstream). I think I rebooted the PCM. I disconnected the battery and then reconnected it. Is that enough?


No for most reboots take at least 10 minutes.If you don't need it i would leave it over night.
 
Started it back up. It was a little rough at first but it's idling fine now around 6-700ish. Error code went away too. I'll drive it around more tonight to see if the error code pops back up.
 
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