I’m needing some expert advice. I have a #4-cylinder misfire. We have swapped the coil, spark plug, wire, and fuel injector with the opposite side of the block. The problem does not follow to the other cylinders still showing code P0304. I have had a mechanic do a compression test it passed with all cylinders are around 120psi. They have pulled the valve cover and checked the rocker arm movement. They all checked well. We were told it could be a vacuum leak from the intake manifold. So, We removed and replaced the gaskets with new ones, still have a misfire. We did notice after removing the intake the cylinder seemed dry. I really do not know where to go from here any advice would be appreciated.
Initial Thoughts
You have been doing things right as far as checking and testing. And I commend you on not giving up.The fact that you said that the problem cylinder seemed dry is an indicator for me. The fuel injector may not be firing. The injector is good as you swapped it out. But it doesn’t mean the injector itself is being triggered to fire. So the next thing I would do is to test for injector pulse on that cylinder. Use an injector pulse tester if you have one. Once you have ruled that out, you may be looking at internal damage. However, When the MIL is FLASHING the fuel injector may be disabled for the effected cylinder to protect the catalytic converter form being damaged.
Technical Service Bulletin (TSB)
So I looked into this a bit in the manual and there are several TSB’s for a misfire. Doesn’t speak to highly for the manufacturer.
TSB: PIP4138R
States some possible causes:
- Worn camshaft lobe and/or lifter roller
- A sticking valve
- Valve leakage
- A broken valve spring
- A collapsed AFM (Active Fuel Management) Lifter
Generally, a worn cam lobe on this engine will create a consistent chirp, squeal or tick noise at camshaft speed.
You may want to purchase the manual to read all the TSB information related tot his issue: Purchase Manual as there is 5 pages just on that TSB alone.
Other TSB’s PIP5029H, #16-NA-383, #19-NA-219, PIP4138R, PIP5628E,
P0304 Misfire Testing
Thank you sir! I will definitely try everything you have suggested. I will reply once we find out what the issue is and what we do to fix the misfire.
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