- Joined
- Jun 10, 2026
- Messages
- 1
- Points
- 1
- City
- Redmond
- State - Country
- OR - USA
- Vehicle Year
- 2003
- Vehicle
- Ford Ranger
- Drive
- 2WD
- Engine
- 3.0 V6
- Transmission
- Manual
- Total Lift
- 5.5
- Total Drop
- 0
- Tire Size
- 35"
Hello,
I am new to the forum and I've searched everything I can think of across the internet. I am currently lost on what is causing a misfire on cylinder 6 of my 2003 Ranger 3.0 V6 Gas. I have done every test I can think of or have the ability to perform. They all indicate a "healthy" engine.
A few things about the motor: the codes it throws are P0306 and occasionally P0316. It was rebuilt a few years ago but only has about 1500 miles on it due to being a offroad toy, I did fully break in the motor for the first 1000 miles with light to moderate driving, the truck has JBA shorty headers and a strait piped exhaust. I use a sparkplug extender on the downstream o2 sensor to trick it into thinking the cats are there (seems to work). I have installed a set of Tom Morana Racing 1.8:1 Roller Rockers.
While driving the misfire sounds like a burble in the exhaust, like a dead cylinder makes. The misfire occasionally goes away while driving for random periods of time.
Below is what I have tested.
For the ignition side of things I have gapped and installed new spark plugs (when I removed the spark plugs cylinder 6 looked white and chalky making me think its a lean issue), tested ohms on the spark plug wire and switched it with another cylinder, tested the ignition coil by moving the cyl6 wire to the neighboring tower, I've tried a new ignition coil, I've used a spark plug light to verify spark strength and consistency.
For the fuel side of things I have swapped the cylinder 6 injector with cylinder 3, performed a noid light test on the injector plug and that looked consistent and strong, Inspected the plug wires for damage none was noted, checked fuel rail pressure which sat solid at ~62psi while engines running, I do have a small amount of leak down at the fuel rail with key on engine off but have verified it is due the the pump drain back valve and not a leaky injector, I do not have a way to do a injector balance test because I only have access to FORscan and not a high tech diagnostic tool.
For the air side of things I have checked for vacuum leaks using propane all around the engine and especially near cyl6 intake runner no rpm rise. I can't locate any exhaust leaks around the cylinder 6 but I also don't have a smoke machine.
For the mechanical side of things I have done a compression check with good results all cylinders were within 15psi of each other and around 155psi, I have done a leak down test and all cylinder had only about 3% leak down, I visually inspected the valve rockers and push rods by removing the valve cover and spinning the engine by hand and everything moved freely and nothing looked bent.
None of those diagnostic test or replacement parts moved the misfire or changed the frequency of it.
I have no idea where to go from here. I NEED HELP! What can be causing this? Has anyone had anything like it before?
Thank you in advance for anyone willing to help.
I am new to the forum and I've searched everything I can think of across the internet. I am currently lost on what is causing a misfire on cylinder 6 of my 2003 Ranger 3.0 V6 Gas. I have done every test I can think of or have the ability to perform. They all indicate a "healthy" engine.
A few things about the motor: the codes it throws are P0306 and occasionally P0316. It was rebuilt a few years ago but only has about 1500 miles on it due to being a offroad toy, I did fully break in the motor for the first 1000 miles with light to moderate driving, the truck has JBA shorty headers and a strait piped exhaust. I use a sparkplug extender on the downstream o2 sensor to trick it into thinking the cats are there (seems to work). I have installed a set of Tom Morana Racing 1.8:1 Roller Rockers.
While driving the misfire sounds like a burble in the exhaust, like a dead cylinder makes. The misfire occasionally goes away while driving for random periods of time.
Below is what I have tested.
For the ignition side of things I have gapped and installed new spark plugs (when I removed the spark plugs cylinder 6 looked white and chalky making me think its a lean issue), tested ohms on the spark plug wire and switched it with another cylinder, tested the ignition coil by moving the cyl6 wire to the neighboring tower, I've tried a new ignition coil, I've used a spark plug light to verify spark strength and consistency.
For the fuel side of things I have swapped the cylinder 6 injector with cylinder 3, performed a noid light test on the injector plug and that looked consistent and strong, Inspected the plug wires for damage none was noted, checked fuel rail pressure which sat solid at ~62psi while engines running, I do have a small amount of leak down at the fuel rail with key on engine off but have verified it is due the the pump drain back valve and not a leaky injector, I do not have a way to do a injector balance test because I only have access to FORscan and not a high tech diagnostic tool.
For the air side of things I have checked for vacuum leaks using propane all around the engine and especially near cyl6 intake runner no rpm rise. I can't locate any exhaust leaks around the cylinder 6 but I also don't have a smoke machine.
For the mechanical side of things I have done a compression check with good results all cylinders were within 15psi of each other and around 155psi, I have done a leak down test and all cylinder had only about 3% leak down, I visually inspected the valve rockers and push rods by removing the valve cover and spinning the engine by hand and everything moved freely and nothing looked bent.
None of those diagnostic test or replacement parts moved the misfire or changed the frequency of it.
I have no idea where to go from here. I NEED HELP! What can be causing this? Has anyone had anything like it before?
Thank you in advance for anyone willing to help.
