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Random Multipule Cylinder Misfire
Help me please fellas.
Vehicle-2003 Blazer 4.3 History-Lost 1 injector, ohmed out bad, replaced. 1000 miles later, lost another, ohmed out bad, replace all remaining injectors at this point. New fuel pressure regulater. New plugs/wires. Coil checks good. According to my manual, key on, engine not running, fuel psi should be 55 to 61 psi. Mine runs up to 40, then slowly bleeds down. BUT, with engine at idle, it holds steady at 55 psi. I am about to go crazy!! Any ideas my friends?? Thank you in advance. BTW, that is the only code displayed. |
i wish i could help.. i have the same issue. i have a 95 and i have changed everything. coil, ingintion module, cap, rotor, fuel filter... the only code i get it 300 random cylinder miss fire.
On my first prime it goes to 40 psi. then drops to 11psi. after i get it started it stays at 59psi. and i shut it off it drops to 11psi. To me it seams like that the pump isnt holding the pressure, or the fuel injector assembly is leaking... I feel like a dog chasing his tail. As for your motor i dont know if u have the same set up as mine. sounds like u have an injector for each cyl.... it might be the fuel pump. mine takes a lot of cranks to get started. and then runs very rough. when i change my pump ill c if it wrks.. |
*Moved to '2nd Gen Tech'*
If you will follow through the steps in 96+ Fuel System Diagnosis it will help you pinpoint the cause of the fuel pressure problem. You did not say what the exact DTC code is that you're getting, but we have a section for those also. |
Sorry-P0300.
All that info looks like a good start. Thank you. |
Your manual must be a Haynes or a Chilton, they're wrong on the fuel pressure for 1996 and newer, (along with several other things). According to the GM "dealer issue" shop manual, key ON, engine OFF, fuel pump running, pressure must be 60psi to 66psi, and must remain above 55psi for 10 minutes after the fuel pump shuts off. Usually P0300 is caused by secondary ignition faults such as plugs, plug wires, distributor cap, rotor, and ignition coil BUT, low fuel pressure can also set a P0300. Check the link that rriddle3 posted, it will walk you right through diagnosis.
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Originally Posted by Captain Hook
(Post 371352)
Your manual must be a Haynes or a Chilton, they're wrong on the fuel pressure for 1996 and newer, (along with several other things). According to the GM "dealer issue" shop manual, key ON, engine OFF, fuel pump running, pressure must be 60psi to 66psi, and must remain above 55psi for 10 minutes after the fuel pump shuts off. Usually P0300 is caused by secondary ignition faults such as plugs, plug wires, distributor cap, rotor, and ignition coil BUT, low fuel pressure can also set a P0300. Check the link that rriddle3 posted, it will walk you right through diagnosis.
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Just bought a 3 volume set on E Bay. Should have done that long ago.
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so i took off my intake manifold off today and it was soaked in gas. i had a friend turn the key on and the plastic hoses that lead to the spider was spraying out. i was getting a p300 code as well. some times i got a rich code.
I changed the plugs, coil, module, cap and rotor, seafoamed the crap out of it. and no luck it just got worse. i think i may have found the problem now. So i was wondering if i can change the hoses out with something else. like high pressure fuel line. or do they sell the hoses. i need my truck back. but i hope this helps u o yeah id turn the key on and it would pressurize to 60 then drop right away. down to 5psi. when running it stayed at 59psi. it would hold 59psi at idle. but ran like crap. thank your and i hope some one has a solution for the leaky hoses for me. i cant afford the assembly but i need to fix these hoses some how today. |
Originally Posted by chucky blazer
(Post 371514)
so i took off my intake manifold off today and it was soaked in gas. i had a friend turn the key on and the plastic hoses that lead to the spider was spraying out. i was getting a p300 code as well. some times i got a rich code.
I changed the plugs, coil, module, cap and rotor, seafoamed the crap out of it. and no luck it just got worse. i think i may have found the problem now. So i was wondering if i can change the hoses out with something else. like high pressure fuel line. or do they sell the hoses. i need my truck back. but i hope this helps u o yeah id turn the key on and it would pressurize to 60 then drop right away. down to 5psi. when running it stayed at 59psi. it would hold 59psi at idle. but ran like crap. thank your and i hope some one has a solution for the leaky hoses for me. i cant afford the assembly but i need to fix these hoses some how today. |
Originally Posted by chucky blazer
(Post 371514)
so i took off my intake manifold off today and it was soaked in gas. i had a friend turn the key on and the plastic hoses that lead to the spider was spraying out. i was getting a p300 code as well. some times i got a rich code.
I changed the plugs, coil, module, cap and rotor, seafoamed the crap out of it. and no luck it just got worse. i think i may have found the problem now. So i was wondering if i can change the hoses out with something else. like high pressure fuel line. or do they sell the hoses. i need my truck back. but i hope this helps u o yeah id turn the key on and it would pressurize to 60 then drop right away. down to 5psi. when running it stayed at 59psi. it would hold 59psi at idle. but ran like crap. thank your and i hope some one has a solution for the leaky hoses for me. i cant afford the assembly but i need to fix these hoses some how today. |
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