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 (TRS), 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 overlanding 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 adventures. TRS has been heavily referenced by enthusiasts, mechanics, and off-road builders looking for practical, experience-based information.