MIL Service Engine Soon Light On with DTCs P0300 and/or P0301-P0304, Engine Misfire

Vehicles equipped with DOHC (LL0) engines may experience the malfunction indicator lamp (MIL) (SERVICE SOON telltale lamp) ON with DTCs P0300 and/or P0301, P0302, P0303, or P0304.

Misfire DTCs can be caused by a number of conditions. Several of these conditions are addressed in this bulletin.

1. Electrical - ignition secondary, mechanical or fuel system component(s) malfunctioning.
2. Misfire caused by cold-start spark plug fuel-fouling or misfire DTCs setting inappropriately during non-catalyst damaging events, (calibration).
3. Some lifters and valve spring combinations not allowing the exhaust valves to close properly during initial start-up.
4. Deposit build-up on exhaust valves guides and exhaust valve stems, causing the exhaust valves to close too slowly during engine warm-up and hot driving conditions.

Refer to the Misfire Diagnostic Charts within this bulletin.

Important: Do not clear DTCs until entire diagnostic procedure has been completed. Failure record data will be required for accurate diagnosis.

Notes on the Diagnostic Chart 1:

1. Other E1 and/or fuel injector DTCs may lead to the primary condition that has resulted in the setting of the misfire DTC. DTCs such as P0201, P0202, P0203, P0204, P0336, P0340, P0341, P0351, P0352, P0506 and/or P0507 should be diagnosed prior to the misfire DTC. Refer to the appropriate year Powertrain Controls Service Manual.
2. Refer to Technical Information Bulletin 96-T-25, "Engine Cranks but will not Start, or Engine Stalls Immediately After Start Followed by Extended Engine Cranking and/or Ignition Misfire Resulting in DTCs P0300, P0301, P0302, P0303, P0304 (Replace Spark Plugs and Install New Emissions Label)."
3. Carbon tracking on the spark plug porcelain insulator could easily be confused with darkened dielectric grease. To distinguish grease from carbon tracking, clean the spark plug insulator with a rag and solvent such as Saturn Brake and Choke Cleaner P/N 21007432 (or equivalent). Carbon tracking produces gray-black lines that cannot be removed from insulator.

flowchart

The steps in the Diagnostic Chart that contain number (e.g. 1) refer to the notes below. These notes provide additional detail on those specific steps in the Diagnostic Chart.

Notes on the Diagnostic Chart 2:

1. To select the Scan tool misfire screen, from the SYSTEM SELECTION menu, select POWERTRAIN, DATA DISPLAY, ENGINE DATA DISPLAY, and MISFIRE DATA.
2. Counts in MISFIRE CURRENT CYL. #1, 2, 3, 4 indicates current misfires are being detected on the associated cylinder(s). If counts remain at 0 (zero) no misfires are being detected.
3. Misfire counts increasing at equal or near-equal rates on coil-pack cylinder pairs (1 and 4, or 2 and 3) could be caused by inaccurately learned crankshaft characteristics.
4. Crankshaft Relearn Procedure:

4.1.	From the SYSTEM SELECTION menu, select POWERTRAIN, SPECIAL FUNCTION, and CRANKSHAFT POS. VARIATION LEARN.

4.2.	Follow Scan tool on-screen instructions to relearn crankshaft variation.

flow chart

The steps in the Diagnostic Chart that contain a circled number (e.g 1) refer to the notes below. These notes provide additional detail on those specific steps in the Diagnostic Chart.

Notes on the Diagnostic Chart 3:

1. Fuel sample separation into layers is an indicator that there may be water in the fuel, which would cause an intermittent misfire on all cylinders. Replacing the fuel supply can confirm this as the cause.

flow chart

The steps in the Diagnostic Chart that contain a circled number (e.g. 1) refer to the notes below. These notes provide additional detail on those specific steps in the Diagnostic Chart.

Notes on the Diagnostic Chart 5:

When the ignition secondary shorts (path other than through spark plug) a misfire results. This step checks for the type of ignition secondary system break-down that would result in such a short. To effectively do this procedure use a 10 percent saltwater solution. Start misting the EI module and spark plug terminals at the EI module first, then mist each spark plug wire from EI module to the plug. Look and listen for spark to jump from any of the ignition secondary components.

Important: After saltwater spray test is completed, engine compartment must be rinsed thoroughly with clean water.

Procedure 1 - EI Module Coil Corrosion Cleaning

1. Remove corrosion from EI module coil terminals using a 3M Scotch-BRITE fiber pad or equivalent. Do not use any solvents or cleaners to aid in removal. Do not contact or scratch the plastic sealing surfaces below the terminal. If the coil tower terminals are damaged by corrosion (e.g. pitting), replace coil.
2. Replace corroded spark plug wire(s) with new service spark plug wires. Add a liberal amount of dielectric grease to EI module coil terminals before installing the new spark plug wires.
3. Return to and continue Misfire Diagnostic Chart 1, Ignition Secondary Inspection step 3.

Procedure 2 - Service Exhaust Spring, Seal and Lifter Installation (Cylinder Head Not Removed)

Important: For the following procedures, refer to "Camshaft And Lifter Replacement In-Vehicle (Front Cover In Place)," and "Valve Spring And Stem Seal Replacement In-Vehicle" in the "DOHC (LL0) Cylinder Head" section of the appropriate year "Engine/Fuel/Air Intake/Exhaust Service Manual."

Install new:

Important: DO NOT install Exhaust Valve Oil Seal (P/N 210006516) on DOHC intake valves. Excessive oil consumption could result. If replacing Intake Valve Oil Seals, use P/N 21006515.

The Service Exhaust Lifter may be identified by a blue coloration on the center surface of the lifter and/or the part number inked onto the lifter inner diameter (Figure 2). Neither of these identification methods are permanent and may not be visible after prolonged storage and/or use.

Procedure 3 - Cut Exhaust Valve Guides (1996 and 1997 up to VZ318805)

Important: This procedure should not be required on 1997 vehicles after VZ318805. These vehicles were produced with square-cut (non-chamfered on the inside diameters) valve guides and therefore should not develop deposit build-up.

Important: For the following procedures, refer to "DOHC (LL0) Cylinder Head" section of the appropriate year "Engine/Fuel/Air Intake/Exhaust Service Manual."

1. Remove cylinder head assembly.
2. Remove exhaust camshaft and lifters. (Do not remove intake camshaft and lifters.)
3. Remove and discard exhaust valves, spring and seals. (Do not remove intake valves, spring or seals.)
4. Clean carbon and varnish from the inside diameter of all the valve guides using a metal or nylon valve guide brush driven by an electric drill and solvent.
5. Using Saturn Valve Guide Go/No-Go Gauge (J43120), measure exhaust valve guides.

Notice: The Go (green) end of gauge should go through the entire length of valve guide with light and uniform pressure. Use of excessive force will result in tool and/or guide damage.

5.1.	Insert Go (green) end of gauge into valve guide from either the combustion chamber side or the camshaft side.

If gauge passes through guide with light and uniform pressure, proceed to step 5.2.

If gauge will not pass through guide with light and uniform pressure, clean guide again as instructed in step 4 and repeat guide measurement. If gauge still will not pass through guide, refer to the appropriate model year Saturn Engine/Fuel/Air Intake/Exhaust Service Manual for valve guide repair and/or replacement procedures.

Notice: The No-Go (red) end of gauge should NOT enter either end of valve guides. Use of excessive force will result in tool and/or guide damage.

5.2.	Attempt to insert No-Go (red) end of gauge into both ends of valve guides.

If gauge does not enter either end of guide, then guide is within correct specifications for diameter, straightness, and roundness.

5.3.	If gauge enters either end of guide, the guide is oversized beyond specifications. Refer to the appropriate to the appropriate model year Saturn Engine/Fuel/Air Intake/Exhaust Service Manual for valve guide repair and/or replacement procedures.




6. Place cylinder head, with combustion chamber side facing up, on 2 x 4 wood blocks on the shop floor or suitable workbench.

Important: Review the following information before using the SA9704E-A, End Mill Cutter (piloted counter-bore) W/Stop Collar:

•	Use a 1/2 horsepower variable or low speed electric drill motor,

•	Use DOHC (black) plastic stop collar,

•	Stop collar must be located so that the set screw aligns with end mill grove,

•	DO NOT use cutting fluid,

•	Use drill speed of approximately 500 rpm,

•	Apply pressure straight onto valve guide,

•	DO NOT side load tool during operation,

•	Some smoking may occur during the cutting process, (this is normal and tool life is not affected).

7. Using tool SA9740E (Valve Guide End Mill Cutter) with DOHC (black) plastic stop collar, cut the exhaust valve guides from the combustion chamber side. The plastic stop will make contact with the valve seat when the end mill has completed the specified amount of guide removal (approximately) 3mm [1/8 in.]). (Refer to illustration.)

Important: Do not use a reamer as a cleaning tool. Machine/drill driven reamers typically need a minimum of .0762 mm (0.0003 in.) material cut to operate correctly and to create the desired surface finish. Attempting to use a machine/drill operated reamer without removing material may cause the reamer to bind, will burnish/smear instead of cutting the guide material and will result in decreased tool life.

8. Clean the valve guide debris, created from the cutting operation, from the cylinder head with solvent.

Important: Some carbon deposits and minor pitting on the valve seat is normal. If deposits or pitting is excessive, valve refacing or replacement should be performed by a qualified machine shop.

9. Clean carbon deposits from the valve seat surface with solvent and a 3M Scotch-BRITE fiber pad (or equivalent).

Important: For the following procedures, refer to "DOHC (LL0) Cylinder Head" section in the appropriate year "Engine/Fuel/Air Intake/Exhaust Service Manual" for cylinder head assembly.

10. Install new:

•	Exhaust Valves (P/N 21007154),

•	Exhaust Valve Springs (P/N 21008589).

•	Exhaust Valve Lifters (P/N 21015000), and

•	Exhaust Valve Oil Seals (P/N 21006516 - brown in color).

Important: DO NOT install Exhaust Valve Oil Seal (P/N 21006516) on DOHC intake valves. Excessive oil consumption could result. If replacing Intake Valve Oil Seals, use P/N 21006515.

11. Install cylinder head assembly.
12. Verify the condition has been repaired by repeating the condition that are in malfunction history, if possible. Refer to FAILURE RECORD DATA screen. Attempt to reproduce the condition under the same operating conditions recorded in the FAILURE RECORD DATA screen. Of particular value are the condition of engine coolant temperature (ECT), throttle position (TP) angle, engine speed, vehicle speed, current gear, and torque converter clutch (TCC) engaged.

Procedure 4 - Service Calibrations

Install new PCM calibration according to the calibration in the following PCM Calibrations (Calibration ID) chart. (Refer to "Service Programming System" in the Service Stall System User Guide.)

Important: On 1996 and newer vehicles, it is necessary to perform the crankshaft relearn procedure after reprogramming PCM. Refer to the following:

Crankshaft Relearn Procedure: