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Driveability TSBs '84-89
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For other TSBs, check here.
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TSB 89-12-09 Driveability 351HO

Publication Date: JUNE 14, 1989

LIGHT TRUCK: 1984-87 ECONOLINE, F SUPER DUTY, F-150, F-250, F-350
MEDIUM/HEAVY TRUCK: 1984-87 F & B SERIES

ISSUE: A rich running engine at high altitude may be caused by incorrect vacuum hose and electrical connections. The overly rich condition can cause stalling, hard starting, or poor fuel economy.

ACTION: Listed below are some incorrect vacuum and electrical connections that have been found in the field. Technicians should check for these conditions before trying further diagnosis.
* Spark port or EGR port vacuum supplied to 5" and 10" Hg. vacuum switch instead of manifold vacuum.
* Manifold vacuum signal applied to off-idle vacuum switch instead of EGR port vacuum signal.
* Wrong vacuum hose routing for the altitude compensator system (check vacuum schematic).
* Wrong electrical connections - like connecting a wire to a 7V source when it should be connected to a 12V power source.
* Vacuum filter is restricted or plugged by a cap or other object.

OTHER APPLICABLE ARTICLES: 86-12-17
WARRANTY STATUS: INFORMATION ONLY