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

Vehicles equipped with SOHC (L24) engines may experience the malfunction indicator lamp (MIL) (SERVICE ENGINE 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 inappropriate during non-catalyst damaging events, (calibration).
3. Deposit build-up on exhaust valve 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.

Begin with the Diagnostic Chart on the facing page. 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 1:

1. Other set EI 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, 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. Validation of the ignition secondary is the first, and most critical step in the diagnosis of the misfire condition. Diagnosis steps in this block will validate the ignition secondary on a component level.
4. 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). Carbon tracking produces gray--black lines that cannot be removed from the insulator.

missing flowchart

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 2:

1. 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 the 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.

•	If a break-down is identified between either of the coils and ground, replace the affected coil(s).

•	If a break-down is identified at a coil to spark plug wire interface, assure that the wire was assembled with sufficient dielectric grease. If break-down continues, replace the suspect wire and affected coil(s).

•	If the break-down is identified along the length of the spark plug wire, replace the suspect wire.

•	If a break-down is identified at the spark plug end, replace the spark plug and/or wire as necessary.

2. To select the Scan tool misfire screen, from the SYSTEM SELECTION menu, select POWERTRAIN, DATA DISPLAY, ENGINE DATA DISPLAY and MISFIRE DATA.
3. 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.
4. 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.
5. Crankshaft Relearn Procedure:

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

5.2.	Follow Scan tool on screen instruction to relearn crankshaft variation.

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Procedure 1 - Cut Exhaust Valve Guides (1996 and 1997 up to VZ350909)

Important: For the following procedures, refer to "SOHC (L24) Cylinder Head" section of the appropriate year Engine/Fuel/Air Intake Exhaust Service Manual.

1. Remove cylinder head assembly.
2. Remove complete rocker arm assembly and all hydraulic lifters.
3. Remove and discard exhaust valves, and seals. (Reuse exhaust valve springs, caps, keys and hydraulic lifters. Do not remove intake valves, springs or seals.
4. Clean carbon and varnish from 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- 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 of the camshaft side.

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

•

If gauge will not pass through valve guide with light and uniform pressure, clean valve guide again, as instructed in step 4, and repeat valve guide measurement. If gauge still will not pass through valve guide, refer to the appropriate model year Saturn/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.

•	If gauge enters either end of guide, the guide is oversized beyond specifications. Refer 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, Valve Guide End Mill Cutter (piloted counter-bore) W/Stop Collar:

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

•	Use SOHC (blue) plastic stop collar,

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

•	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 service tool SA9704E (Valve Guide End Mill Cutter) with SOHC (blue) 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 10 mm [3/8 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 (0.003 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 solvent.
9. Clean carbon deposits from the valve seat surface with solvent and a 3M™ Scotch-Brite fiber pad (or equivalent).

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

10. Install new:

•	Exhaust Valve Oil Seals (P/N 21006515)

•	Exhaust Valves (P/N 21007040)

11. Install cylinder head assembly.
12. Verify the condition has been repaired by:

12.1.

Start engine and increase engine speed to 3500 rpm.

12.2.

Hold engine rpm at 3500 rpm for approximately 30 seconds.

12.3.

Release accelerator, allowing engine to return to idle rpm and observe for engine miss or popping noise. It may be necessary to repeat this step throughout the entire engine warm-up cycle until normal operating temperature of 88°C (190°F) is achieved.

Procedure 2 - Service Calibrations

Reprogram the PCM according to the "PCM Calibrations (Calibration ID)" table listed below. (Refer to "Service Programming System" in the Service Stall System User Guide.)

Important: On 1996 vehicles, it will be necessary to perform the crankshaft learning procedure. (Refer to note 5 of Chart 2 in this bulletin.)

To receive credit for this repair during the warranty coverage period, submit a claim through the Saturn Dealer System as follows: