Technical Service Bulletins
|Publication Date: AUGUST 26, 1999|
This TSB article is being republished in its entirety to include 1998 and 1999 model year vehicles.
Some vehicles may backfire on acceleration. This may occur at all ambient temperatures and may be caused by excessive Intake Valve Deposit (IVD). This may be due to carbon deposits on the intake valves.
Perform diagnostics and clean intake valves if required. Refer to the following Service Procedure for details.
- Perform normal diagnostics found in the 1997 Powertrain Control/Emissions Diagnosis (PC/ED) On-Board Diagnostic II (OBD-II) Service Manual or the latest version CD-ROM in Service Bay Diagnostic System (SBDS) or Service Bay Technical System (SBTS). Service as required.
- On vehicles built prior to 4/16/1997, check to see if TSB 97-12-9 has been performed. If not, reprogram the Powertrain Control Module (PCM) per TSB using SBDS or New Generation Star (NGS) Tester. Use April 1997 level CD-ROM calibration or later. Also, replace the (AWSF-42E-EG or -EE) spark plugs with the Spark Plugs (AGSF-34E-E) per TSB 97-12-9.
- If normal diagnostics in Step 2 have not resolved the driveability concern, proceed with the following Intake Valve Deposit Inspection Procedure.
INTAKE VALVE DEPOSIT INSPECTION PROCEDURE
- Remove any two (2) spark plugs. Use a remote starter switch to bump the engine over until the intake valve is fully open in the cylinder to be inspected.
- Use Rotunda Kit 014-00975 Automotive Borescope or equivalent to inspect the back side of the intake valves through the spark plug holes for the presence of carbon deposits.
CAUTION: DO NOT BUMP THE ENGINE WITH THE BORESCOPE IN THE SPARK PLUG HOLE OR ATTEMPT TO VIEW THE VALVE WHILE ROTATING THE ENGINE. THIS MAY RESULT IN BORESCOPE OR ENGINE DAMAGE. CAUTION: DO NOT POWER THE BORESCOPE LIGHT SOURCE FROM A CAR BATTERY WHILE IT IS UNDER CHARGE. FOR EXAMPLE, IF THE ENGINE IS RUNNING, THE LAMP MAY FAIL.
- Compare the deposits with the Intake Valve Deposit Rating System Chart (Figure 1).
- If any of the intake valves appear to have a carbon deposit level of 7 or less (lower number rating), intake valve cleaning is required.
- Proceed to the IVD Cleaning Procedure. Refer to Fuel Recommendation (Figure 2) after cleaning.
- If no carbon deposits are seen or the deposit level is 8 or cleaner, the drive concern may be the result of low volatility fuel (Figure 2).
IVD CLEANING PROCEDURE
|NOTE:||BEFORE BEGINNING THE IVD CLEANING PROCEDURE, USE THE FOLLOWING CARBON BLASTER TIPS.|
Carbon Blaster Tips:
- Be sure that compressed shop air is dry. Drain compressor of water regularly.
- Remove any in-line equipment oilers from the air line to be used with the carbon blaster.
- Be sure to store walnut shells in a watertight container with the lid on.
- Remove unused walnut shells from the carbon blaster when IVD procedure is completed. Do not store walnut shells in carbon blaster.
- Remove the upper intake manifold assembly, fuel rail, and injectors. Refer to the instructions in the appropriate Service or Workshop Manual.
- Tape all EGR orifice cup plugs and intake runners.
- Remove the valve covers and the intake (only) rocker arms.
- Loosely replace the valve covers.
- Perform intake valve carbon cleaning (blasting) procedure, using Rotunda Kit 014-00975 Carbon Blaster in a single cylinder.
- Remove the valve cover for that cylinder, compress the intake valve spring, and rotate the valve 180 degrees.
- Again, loosely replace the valve cover and repeat the blasting procedure.
- Insert Rotunda Kit 014-00975 Automotive Borescope or equivalent through the fuel injector hole into the lower intake manifold to determine complete intake valve carbon removal.
CAUTION: DO NOT ROTATE THE ENGINE WITH THE BORESCOPE IN THE FUEL INJECTOR HOLE. THIS MAY RESULT IN BORESCOPE OR ENGINE DAMAGE.
- Repeat Steps 5 though 8 for each cylinder.
NOTE: DETAILED WRITTEN INSTRUCTIONS AND A PROCEDURAL VIDEO TAPE ARE INCLUDED WITH THE ROTUNDA CARBON BLASTER AND AUTOMOTIVE BORESCOPE KIT.
- Reinstall the rocker arms, valve covers, fuel rail, injectors, and upper intake manifold. Refer to the proper procedure in the appropriate Service Manual.
OTHER APPLICABLE ARTICLES:
Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage
|991808A||Perform Intake Valve Deposit (IVD) Inspection||0.5 Hr.|
|991808B||Perform IVD Cleaning||2.8 Hrs.|
|991808C||Extra Time To Reprogram Powertrain Control Module (PCM) And Replace Spark Plugs||0.6 Hr.|
|BASIC PART NO.||CONDITION CODE|
Figure 1 – Article 99-18-8
Figure 2 – Article 99-18-8