Home Bronco TSB Summaries Recent Updates Gallery Submit A Link Unique Visitors: 314448	FORD BRONCO -> TECHNICAL SERVICE BULLETINS (TSBs) -> Driveability TSB 89-12-09 for 84-89 351HO Econoline & F Series WELCOME to MIESK5's BIG BRONCO LINKS - We now have over 23,000 LINKs! This is a Ford Bronco, Truck & Van Technical & Parts LINKS site developed by the MIESK5 Family & is not affiliated with the Ford Motor Company in any manner. Although we initially developed this site for 78-96 Big Broncos, information in many Links also applies to Ford Trucks, Vans & Cars. Select A Link: Driveability TSB 89-12-09 for 84-89 351HO Econoline & F 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... READ MORE Source: by Ford via Steve83 (Steve, That dirty old truck) at SuperMotors.net