Engine - Stalls After Start: Overview
No: 91-T-35BDATE: November, 1993
GROUP: Engine
CORP. NO.: 186301R
SUBJECT:
Engine Stalls after Start, SOHC (LKO) Engines (Clean TBI Unit, Replace TBI Gasket or Install New PCM Calibration)
Due to the following revisions, this bulletin supercedes bulletin 91-T-35A, which should be discarded.
^ Addition of 1993 and 1994 vehicles
^ Removal of faulty intake manifold casting surface inspection procedure
^ Revisions to diagnostic charts to simplify procedures
^ Fuel pressure specification changes in diagnostic charts
^ Removal of some service part numbers
MODELS AFFECTED:
1991-1994 Saturns equipped with SOHC (LKO) Engines.
CONDITION:
Some owners of 1991-94 Saturns equipped with SOHC (LKO) engines may experience one or more of the following conditions:
^ If the vehicle is equipped with an automatic transaxle, the engine may stall after the vehicle is initially started, or stalls or stumbles when first shifted into gear.
^ If the vehicle is equipped with a manual transaxle, the engine may stall after the vehicle is initially started, when the vehicle is at a complete stop and the steering is turned to its maximum left or right position, or during launch when the engine is cold.
CAUSE:
These conditions may be caused by: Loss of fuel pressure, throttle body injector (TBI) unit gasket protruding into the throttle bore (1991-1992 through VIN NZ 151498) and/or engine calibration.
^ Possible causes for the loss of the fuel pressure include the TBI fuel pressure regulator assembly valve not seating due to debris, or leaking fuel pump check valve, fuel line or injector. This condition can cause the engine to stall immediately after start usually within 15 seconds.
The gasket between the TBI unit (all 1991 and 1992 engines built before and including VIN NZ151498) and intake manifold can protrude into the throttle body bore causing fuel to puddle on it.
The engine calibration (1991-1992 vehicles only) can cause a start/stall condition due to the calibration supplying a lean start-up fuel mixture, if the ambient temperatures are between 20-56°C (68-133° F). This condition can occur during initial start and/or after the engine has been operated for one minute or more.
IMPORTANT:
The new engine calibration must only be installed if the vehicle's TBI unit gasket has been replaced, fuel and/or engine electronic control system are found to be operating properly.
If the fuel system will not hold pressure, the TBI unit must be cleaned with air pressure to eliminate debris that may cause an intermittent start/stall condition. Follow the TBI unit cleaning procedures in this bulletin.
IMPORTANT:
After the start/stall calibration has been installed, the customer may notice a slight vehicle hesitation on initial launch, if the engine is allowed to idle for more than 90 seconds. This slight hesitation goes away when the coolant temperature 'warms up a few degrees or the vehicle is driven immediately after initial engine start.
CORRECTION:
If the start/stall condition is verified, proceed to the following figures to repair the concern.