EXPERTEC TSB (91-T-35B-SATURN)

Publication date: 1993-11-01
Reference number: 91-T-35B-SATURN

EXPERTEC TSB

TECHNICAL SERVICE BULLETIN

Reference Number(s): 91-T-35B-SATURN, Date of Issue: November 1, 1993
Superceded Bulletin(s): 91-T-35A

ENGINE STALLS AFTER START - CLEAN TBI/INSTALL NEW PCM CAL

Model(s): 1991-94 Saturn Vehicles

Bulletin No.: 91-T-35B-SATURN

Date: November 1, 1993

NOTE: Due to the following revisions, this bulletin supersedes 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.

SUBJECT

Engine Stalls after Start, SOHC (LKO) Engines (Clean TBI Unit, Replace TBI Gasket or Install New PCM Calibration).

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. See Fig 1 - Gasket Protruding Into The Throttle Bore.
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 degrees Celsius (68-133 degrees Fahrenheit). This condition can occur during initial start and/or after the engine has been operated for one minute or more.

NOTE: 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.

NOTE: 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 concern is verified, proceed to the following chart (See Fig 2 thru Fig 4 - Stall/Start System Diagnostic Flow Chart) to repair the concern.

NOTE: Run engine for three minutes before each fuel system pressure and leakdown test to purge air from the fuel system. Allow pressure gage to stabilize before beginning five minute leakdown test. Engine should be tested at ambient temperature. Do not install the PCM Start/Stall calibration if the fuel system and/or TBI unit gasket are found to be defective.

PROCEDURES

TBI UNIT AIR PRESSURE CLEANING PROCEDURE (ALL 1991 THROUGH 1994 SATURNS WITH SOHC [LKO] ENGINES)

CAUTION: DO NOT ALLOW SMOKING OR THE USE OF OPEN FLAMES IN THE AREA WHERE WORK ON THE FUEL SYSTEM IS TAKING PLACE. ANYTIME THE FUEL SYSTEM IS BEING WORKED ON DISCONNECT THE NEGATIVE BATTERY CABLE, EXCEPT FOR THOSE TESTS WHERE BATTERY VOLTAGE IS REQUIRED.

Remove fuel tank fill cap.
CAUTION: WHENEVER FUEL LINE FITTINGS ARE LOOSENED OR REMOVED, WRAP A SHOP CLOTH AROUND THE FITTING TO COLLECT FUEL. PLACE THE CLOTH IN AN APPROVED CONTAINER.
Use Gage Bar Kit SA9127E, connect the air pressure regulator to the 0-69 kPa (0-100 psi) pressure gage (refer to Fig 5 ). Install fuel pressure test port adapter, bleed fuel into an approved container and close adapter shutoff valve. Connect hose from fuel pressure test port adapter to the air pressure regulator outlet. Set air pressure regulator to zero. (Regulator shutoff valve must be open.)
Connect a shop air line, capable of supplying 620 kPa (90 psi) air pressure to the air pressure regulator inlet.
Slowly adjust air pressure to 276 kPa (40 psi) for 10 seconds and then back to zero. The air pressure will push fuel contained in the TBI unit back to the fuel tank.
Place a shop towel under the fuel return line connectors and remove the connectors using service tool SA9157E. Cover both openings (fuel return inlet/outlet) with shop cloths to catch debris and fuel. Adjust air pressure regulator to a minimum of 414 kPa (60 psi). DO NOT exceed a maximum of 517 kPa (75 psi). Allow the fuel pressure regulator diaphragm assembly to oscillate (buzz) for one minute.
NOTE: If the fuel pressure diaphragm does not oscillate (buzz), use service tool SA9106E (MFI Throttle Body Minimum Air Tool) and momentarily plug the steel fuel return line opening. The plug may have to be inserted and removed several times until the diaphragm begins to oscillate (buzz). If the diaphragm will not oscillate, replace the diaphragm assembly following the procedures in the "Fuel/Air Intake/Exhaust Service Manual." After the fuel pessure regulator valve has been replaced, test the fuel system again using the procedures in the service manual.
Set the air pressure regulator back to zero and disconnect the shop air line. Remove the air pressure regulator.
NOTE: Whenever fuel line connectors are disconnected, lubricate steel line male ends with clean engine oil. Holding steel line, firmly press on female connector until click is heard, then pull back to confirm engagement. Make sure the fuel line connectors are fully seated. Pinched, kinked or damaged fuel lines must be replaced.
Install fuel return line connector. Pull back on the connector to make sure it is engaged correctly.
Run the engine from three to five minutes with the fuel pressure hose connected to the 0-69 kPa (0-100 psi) gage. Perform a fuel system pressure test and check fuel system leakdown. Refer to specifications provided in this bulletin and to the "Fuel/Air Intake/Exhaust Service Manual" for procedures. If the system does not pass the pressure or leakdown test, replace the fuel pressure regulator assembly or fuel pump assembly following the procedures in the "Fuel/Air Intake/Exhaust Service Manual."
Install fuel tank fill cap, run engine and check for fuel leaks.

PCM CALIBRATION

NOTE: Before installing a new calibration, make a note of the transaxle calibration installed and download the same transaxle calibration with the correct new engine calibration. The new service PCM calibrations are:

1991 NEW CALIBRATION (SOHC [LKO] ENGINES)

1309 Manual Transaxle
1312 Automatic Transaxle (Production release)
1316 Automatic Transaxle (Use when idler gear noise calibration is installed)

NOTE: Refer to Technical Service Bulletin 93-T-05, "SOHC (LKO) Engine Stalls or Hesitates During Open to Closed Loop Transition at Cold Temperatures" for additional information on 1991 SOHC (LKO) engines.

NOTE: This calibration will replace the production calibration. The service stall system screen should read "EC Calibration Start/Stall Only."

Only vehicles built with the latest PCM can be reprogrammed with the new calibration. Vehicles with earlier versions of the PCM require replacement of the PCM before reprogramming.

To determine if the PCM can be reprogrammed with this service calibration, check the TCM ID TABLE with the portable diagnostic tool (PDT) or the service stall system. If the TC EPROM SW ID is 4666, the PCM will have to be replaced. The new version of the PCM will have a TC EPROM SW ID of 1465.

If the PCM has to be replaced, refer to the "Powertrain Control Module" removal and installation procedures in the "Powertrain Control Module" section of the "Electronic Engine Controls Service Manual."

If the TC EPROM SW ID is 1465, refer to "Reprogramming EEPROM" in the "System Utilities" section of the "Service Stall System (SSS) User Guide" for procedures on reprogramming with the service calibration.

1992 NEW CALIBRATION (SOHC [LKO] ENGINES)

0740 Manual Transaxle (Production Release)
0748 Automatic Transaxle (Production release)

NOTE: These calibrations will replace the early production 1992 calibrations. The service stall system screen should read "EC Calibration-Superseded In Production."

PARTS REQUIREMENTS

21006914 Gasket - Throt Body
21007075 Gasket Kit -TBI Asm (Includes Diaphragm Asm)

Fig 1: Gasket Protruding Into The Throttle Bore

Fig 2: Stall/Start System Diagnostic Flow Chart (1 Of 3)

Fig 3: Stall/Start System Diagnostic Flow Chart (2 Of 3)

Fig 4: Stall/Start System Diagnostic Flow Chart (3 Of 3)

Fig 5: TBI Unit Air Pressure Cleaning Procedure

CLAIM INFORMATION

To receive credit for this repair, submit claim through the Saturn Dealer System as follows:

CLAIM INFORMATION

Case Type	Description	Labor Operation Code	Time
VW	TBI Unit Gakset - Replace (1991-1992 Vehicles Only)	T9567	0.9 Hrs
VW	Clean TBI Unit Pressure Regulator With Air (Includes Fuel System Pressure Test)	T9952	0.6 Hrs
VW	TBI Pressure Regulator Assembly Diaphragm -Replace (Includes Fuel System Pressure Test)	J5560	0.5 Hrs
VW	EC Calibration Start/Stall PCM Recalibration (1991-1992 Vehicles Only)	T9549	0.3 Hrs