Engine - Rough Idle/Driveability Concerns

91chevy28

Number: 91-442-6E

Section: 6E

Date: NOV. 1991

Corporate Bulletin No.: 136005

ASE No.: A1


Subject: COLD DRIVEABILITY DIAGNOSIS


Model and Year: 1989-91 GEO METRO


Various cold driveability concerns or hot deceleration stall may be resolved by installation of appropriate updated parts as indicated below:

If the vehicle experiences a cold, extremely rough idle (often described as a "floating", non-cylinder specific miss) and rough running on acceleration, as well as a possible hot deceleration stall, install revised cylinder head, P/N 96065427 plus 6 revised lash adjusters, P/N 5235455 per Service Manual procedures. Installation of a new camshaft should be based on the presence and degree of wear, scratching or pitting of the cam contact area of the original lash adjusters. DO NOT reuse the original cylinder head bolts - install 8 new head bolts, P/N 96059992.

If the vehicle has normal idle quality after a cold start, but has a smooth hesitation on cold acceleration, or if the vehicle starts and runs good cold but after approximately 1/8 mile of driving begins to lose power with the appearance of running over-rich, install an applicable revised calibration ECM as indicated below:

Transmission Emission Part Number

M/T FED 30009394
CAL 30009392

A/T FED 30009395
CAL 30009393

XFI FED 30009390
CAL 30009391

Parts are currently available from GMSPO.

Labor Operation Number: T1766 Cylinder Head and Adjusters

Labor Time: 4.2Hours
Add .2 With A/C
.2 To clean parts on vehicles over 30,000 miles if necessary.

Labor Operation Number: T1768 ECM (No diagnosis)

Labor Time: .4 Hours