Chasing a cylinder misfre
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Joined: Apr 2022
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From: Rowlett
Chasing a cylinder misfre
Hello everyone. I am new to group and currently chasing a cylinder #3 misfire on a 3.0l
The Ranger itself is a 2003, but the engine is of unkown year. The original engine gave out at 236,000 miles and was replaced with a remanufactured 3.0l about 5 years ago. Truck has run flawlessly until about 35k miles and 6 months ago. Without any other symptom it has developed a hard misfire on the number 3 cylinder with a P0303 and P0316 DTC. Now the fun begins..... The engine runs beautifully and smoothly while cold. Drive it around and get it warm, the misfire becomes evident along with flashing MIL. While driving, the engine shows no perceivable driveability issues. The misfire is only noticeble at idle, not even under load.
In my diagnosis and attempted repair methods, I have:
1. Replaced Ignition coil
2. Replaced all spark plugs
3. Replaced spark plug wires
4. Swapped both upstream o2 sensors
5. Swapped #3 and #2 fuel injectors
6. Replaced upper and lower intake manifold gaskets
7. Checked multiple times fuel injector lead with noid light (operates properly)
8. Performed compression check (cylinders #1 #2 and #3 show same pressure at 150+ psi over 6 compression strokes)
9. Checked everywhere I can for vacuum leaks. At idle, vacuum shows to be about 43 to 44 inches.
10. The fuel pump was replaced from an unrelated incident in march 2020 because it just quit working. Misfire did not present itself until well after it's replacement.
I have taken the vehicle to two shops in the area who have both said there must be some internal engine malfunction and reccommended a tear down. This was after their own compression checks and cylinder balance tests. So thats what I did. I removed the right cylinder head myself and inspected it. I did not see anything out of the ordinary. Cylinder #3 cross hatching looked normal and similar to #1 and #2. The head showed no obvious defect either. I took the head to a machine shop who told me that they found leaking exhaust valves, so instead of getting it rebuilt, I purchased a remanufactured head. I know the engine must itself be pre 1999 because I had the shorter cylinder head bolts and larger 8mm valve stems. After the installation, the exact same issue is present. Runs great cold, cyl #3 misfire when hot with same DTC's.
I'm at my end of what I can think to do so I'm hoping someone in here will help shed some light on this annoying issue.
The Ranger itself is a 2003, but the engine is of unkown year. The original engine gave out at 236,000 miles and was replaced with a remanufactured 3.0l about 5 years ago. Truck has run flawlessly until about 35k miles and 6 months ago. Without any other symptom it has developed a hard misfire on the number 3 cylinder with a P0303 and P0316 DTC. Now the fun begins..... The engine runs beautifully and smoothly while cold. Drive it around and get it warm, the misfire becomes evident along with flashing MIL. While driving, the engine shows no perceivable driveability issues. The misfire is only noticeble at idle, not even under load.
In my diagnosis and attempted repair methods, I have:
1. Replaced Ignition coil
2. Replaced all spark plugs
3. Replaced spark plug wires
4. Swapped both upstream o2 sensors
5. Swapped #3 and #2 fuel injectors
6. Replaced upper and lower intake manifold gaskets
7. Checked multiple times fuel injector lead with noid light (operates properly)
8. Performed compression check (cylinders #1 #2 and #3 show same pressure at 150+ psi over 6 compression strokes)
9. Checked everywhere I can for vacuum leaks. At idle, vacuum shows to be about 43 to 44 inches.
10. The fuel pump was replaced from an unrelated incident in march 2020 because it just quit working. Misfire did not present itself until well after it's replacement.
I have taken the vehicle to two shops in the area who have both said there must be some internal engine malfunction and reccommended a tear down. This was after their own compression checks and cylinder balance tests. So thats what I did. I removed the right cylinder head myself and inspected it. I did not see anything out of the ordinary. Cylinder #3 cross hatching looked normal and similar to #1 and #2. The head showed no obvious defect either. I took the head to a machine shop who told me that they found leaking exhaust valves, so instead of getting it rebuilt, I purchased a remanufactured head. I know the engine must itself be pre 1999 because I had the shorter cylinder head bolts and larger 8mm valve stems. After the installation, the exact same issue is present. Runs great cold, cyl #3 misfire when hot with same DTC's.
I'm at my end of what I can think to do so I'm hoping someone in here will help shed some light on this annoying issue.
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