P0306 misfire
#1
P0306 misfire
I recently rebuilt my 1996 GMC K1500 5.0. Everything is new electrically except the PCM. Distributor, cap, rotor, camshaft sensor, ICM, spark plugs, wires, solenoid, spider injector assembly. Crank shaft sensor, knock sensor, ignition harness, all O2 sensors.
I replaced rod and main bearings all seals and gaskets. I did a compression test on each cylinder after reassembly and all checked out.
when I took it out for the first test drive I got the P0306. I suspected injector issues based on my scanner. I took it to a shop and they confirmed. That’* when I replaced spider injector assembly. Then I got a P0300, which was a vacuum leak at the injector plug and the upper intake housing. I reseated upper intake and made sure of the seal. No vacuum leak now. I took it out yesterday for another test run and I got a P0300 code PCM. So I tried to reset PCM by disconnecting battery and connecting +- cables for 30 min. During the warmup I got P0306 code, scanner says injector. I checked resistance on all injector leads and they all are 13 or 14.
I am at a loss! If anyone has any ideas, I would love to hear them. Thanks in advance!
I replaced rod and main bearings all seals and gaskets. I did a compression test on each cylinder after reassembly and all checked out.
when I took it out for the first test drive I got the P0306. I suspected injector issues based on my scanner. I took it to a shop and they confirmed. That’* when I replaced spider injector assembly. Then I got a P0300, which was a vacuum leak at the injector plug and the upper intake housing. I reseated upper intake and made sure of the seal. No vacuum leak now. I took it out yesterday for another test run and I got a P0300 code PCM. So I tried to reset PCM by disconnecting battery and connecting +- cables for 30 min. During the warmup I got P0306 code, scanner says injector. I checked resistance on all injector leads and they all are 13 or 14.
I am at a loss! If anyone has any ideas, I would love to hear them. Thanks in advance!
#2
Senior Member
Those spider assemblies were a mistake. I would do a running compression test and verify the mechanics or not before chasing other things.
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CathedralCub (03-17-2024)
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CathedralCub (03-17-2024)
#4
Senior Member
True Car Nut
What were the readings?
What is the fuel pressure reading?
What is the fuel pressure reading?
#5
Senior Member
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CathedralCub (03-18-2024)
#6
Fuel pressure is 60
My scanner reads and graphs fuel trim, but I’m not a trained mechanic so I’m not sure how to interpret the fuel trims.
compression on all cylinders were right at 150
My scanner reads and graphs fuel trim, but I’m not a trained mechanic so I’m not sure how to interpret the fuel trims.
compression on all cylinders were right at 150
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CathedralCub (03-19-2024)
#7
Senior Member
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CathedralCub (03-19-2024)
#8
Yes. Started the engine and then shut it off on each cylinder.
the other thing is my scan tool does not read CMP retard. After doing more research, I think I need to have this set. The spec is +-2. I originally had the P1345 code, I repositioned the distributor and the code went away. But I have not had it set by scanning tool. I think this is my next step. I’m also going to recheck for vacuum leaks around cylinder 6 of the intake.
the other thing is my scan tool does not read CMP retard. After doing more research, I think I need to have this set. The spec is +-2. I originally had the P1345 code, I repositioned the distributor and the code went away. But I have not had it set by scanning tool. I think this is my next step. I’m also going to recheck for vacuum leaks around cylinder 6 of the intake.
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CathedralCub (03-19-2024)
#9
Senior Member
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CathedralCub (03-19-2024)
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