Engine Performance - Altitude Adjustment: Overview
86chevy16NUMBER: 86-B-67
GROUP: 6E - Emission Controls
DATE: April, 1986
SUBJECT: ALTITUDE ADJUSTMENTS FOR ENGINE PERFORMANCE
MODELS: ALL 1986 TRUCKS EXCEPT HD DIESEL
THE ADJUSTMENTS SPECIFIED WITHIN THIS BULLETIN ARE INTENDED FOR VEHICLES CURRENTLY IN CUSTOMER USE AND DO NOT APPLY TO NEW VEHICLES IN DEALER INVENTORY. THE ADJUSTMENTS ARE PROVIDED FOR THE PURPOSE OF IMPROVED VEHICULAR PERFORMANCE AND CUSTOMER SATISFACTION ONLY, AND IN NO WAY CONSTITUTE RECERTIFICATION OF EMISSIONS SPECIFICATIONS FOR THE INVOLVED VEHICLES.
This bulletin has been divided into two (2) procedures. Procedure I is applicable to Low Altitude (NA5) trucks taking up permanent residence in a high altitude county. Procedure II is applicable to High Altitude (NA6) trucks being used primarily in low altitude counties. The vehicles which do not require adjustments are those with the closed loop (Computer Command Control) system, which is self compensating for altitude. Applicable 1986 engines that require no adjustments are the 2.5L TBI, 2.8L TBI (S/T Trucks), 4.3L TBI (M Van) and the following engines with California Emissions: 4.3L, 5.0L and 5.7L.