TSB 05-26-3
FORD: 2004-2006 Ranger
ISSUE
Some 2004-2006 Rangers 3.0L-2V “Vulcan” vehicles may exhibit:
– Malfunction indicator lamp (MIL) on with diagnostic trouble codes (DTCs) P0300-P0306 and P0316
– Rough running at various RPM
– Rough idle
– Misfire
ACTION
This may be due to an engine exhaust valve seat recession causing a loss of compression. Refer to the following Service Procedure to diagnose exhaust valve seat recession.
SERVICE PROCEDURE
1. Perform a power balance rest to clarify if a cylinder is misfiring. Identify and keep record of any cylinder that has a concern.
2. Perform a manual compression test with the spark plugs removed to locate any cylinder that may have low compression. Refer to the appropriate Workshop Manual, Engine System, General Information, 303-00.
3. If no low compression is found per shop manual instructions, proceed with normal misfire diagnostics per the Powertrain Controls/Emissions Diagnosis (PC/ED) Manual for the appropriate model year.
4. If low compression is found and it is a cylinder that had a misfire on power balance, perform a leakdown test to determine the source of leakage that may be causing the low compression. Refer to the appropriate Workshop Manual, Engine System, General Information, 303-00.
5. If low compression is found in a cylinder that did not have a misfire detected then proceed with normal base engine diagnostics per the Workshop Manual, Engine System, General Information, 303-00.6.
If the exhaust valve is identified as the source, replace both cylinder heads with the newly released service cylinder heads. Refer to the appropriate Workshop Manual, Section 301-01A.
PART NUMBER / PART NAME
6U7Z-6049-A / Cylinder Head Assembly
2F1Z-6079-BB / Upper Gasket Kit
F8 DZ-6065-AA / Cylinder Head Bolts
F7DZ-9448-BB / Engine Exhaust Gasket
4F1Z-658-AA / Valve Cover Gasket
F6DZ-9439-C / Side Gasket
F2DZ-9A425-AA / China Gasket (Front)
F3DZ-9A424-BA / China Gasket (Rear)
4L5Z-9H486-AA / Gasket-Upper Intake Manifold
About The Author
Jim Oaks is the founder of The Ranger Station, one of the longest-running Ford Ranger enthusiast communities on the web. He has spent over three decades owning, modifying, repairing, and driving Ford Rangers on the street, trail, and cross-country routes.
Since launching TheRangerStation.com in 1999, Jim has documented thousands of real-world Ranger builds, technical repairs, drivetrain swaps, suspension modifications, and off-road tests contributed by owners worldwide. His work has been referenced by enthusiasts, mechanics, and off-road builders looking for practical, experience-based information rather than theoretical advice.
Jim’s hands-on experience includes long-distance overland travel, trail use, drivetrain and axle upgrades, suspension tuning, and platform comparisons across multiple Ranger generations. The content published on The Ranger Station is grounded in first-hand experience and community-verified data, not marketing claims or generic specifications.