Engine Controls - Poor Driveability, False MIL ON
Number: Reissue 86-162Section: 6E
Date: MAY, 1987
Subject: ENGINE CALIBRATION CHANGE: TO
IMPROVE DRIVEABILITY AND ELIMINATE FALSE "SERVICE ENGINE SOON" LIGHTS
Model and Year: 1986 CORVETTE
TO: ALL CHEVROLET DEALERS
Chevrolet Dealer Service Bulletin 86-162 is being reissued to provide a revised calibrator for use on the 1986 corvette with aluminum heads and manual transmission. All copies of Dealer Service Bulletin 86-162 (Section 6E) dated Oct., 1986 should be destroyed.
New service calibrators (Ref: called Mem-Cal in Shop Manual)
have been released for the 1986 Corvette with the 5.7L TPI
engine. These calibrators will address the following
customer comments:
1. "Rough Idle" on both hot and cold engine. The idle speed is raised to 625 plus or minus 25 RPM with automatic transmission and 750 plus or minus 50 with manual
transmission vehicles.
2. "Chuggle or Shudder" at low speeds - Torque converter clutch (TCC) engagement speed is raised to 41 MPH with automatic transmission vehicles.
3. "Surge" at road load - This improvement is for automatic transmission vehicles only.
4. "Engine Overspeed" in 1st gear - This improvement is for manual transmission vehicle only.
5. "Hesitation" on light acceleration with a hot engine.
6. "Service Engine Soon" lights - eliminates the following false codes:
A. Code 33 - Mass Airflow Sensor Voltage Low
B. Code 34 - Mass Airflow Sensor Voltage High
C. Code 43 - Electronic Spark Control (ESC) this correction is for cast iron head Corvettes only (VIN #119016 or earlier).
If normal engine diagnostics and repair do not correct the
above conditions, it will be necessary to replace the
calibrator in the ECM. Below is a listing of the new
calibrators and their usages.
I. On Iron-head Corvettes (VIN #119016 or earlier)
A. Manual Transmission use 1227943
B. Automatic Transmission with 2.59 (GM1) Axle use 1227942
with 3.07 (G44) Axle use 1227944
II. On Aluminum Head Corvettes (VIN #119016 or later) and all convertible models
A. Manual Transmission use 1228473
B. Automatic Transmission with 2.59 (GM1) Axle use 1228107
with 2.73 (GU2)/3.07 (G44) use 1228109
Use applicable Labor Time and Operation Numbers.