Subject: | Engine Misses, Lacks Power, and/or Emits a Popping Noise through Exhaust Manifold on a Deceleration and/or at Idle - SOHC (LKO/L24) Engines (Cut Exhaust Valve Guides) |
Models: | 1991 - 1995 Saturn S-Series vehicles equipped with SOHC (LKO or L24) engines |
Vehicles may miss or lack power under normal engine operating conditions. Also a popping noise may be emitted through the exhaust manifold on deceleration and/or at idle.
These conditions may be caused by:
• | Electrical ignition secondary, mechanical or fuel system component(s) malfunctioning. |
• | Deposit built-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 following diagnostic charts and service procedures. Begin with 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:
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 coils(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. |
Important: For the following procedures, refer to "SOHC (LK0) Cylinder Head" section of the 1991-1994 Engine Mechanical Service Manual or "SOHC (L24) Cylinder Head" section of the Engine/Fuel/Air Intake/Exhaust Service Manual, depending on your vehicle.
Notice: The (Go) green and of gauge should go through entire length of valve guide with light and uniform pressure. Use of excessive force will result in tool and/or guide damage.
- 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 b. |
• | If gauge passes through guide with light and uniform pressure, clean guide again as in step 4 and report 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. |
- 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 specification 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. |
1. Please 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, Valve Guide End Mill Cutter 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 cutting fluid, |
• | Use drill speed of approximately 500 rpm. |
• | Apply pressure straight onto valve guide, |
• | DO NOT side load tool during operation, |
• | Some smoke may occur during the cutting process, (this is normal and tool life is not affected). |
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.
Important: Some carbon deposits and minor pitting on the valve seat is normal. If deposits pitting is excessive, valve seat refacing or replacement should be performed by a qualified machine shop.
• | Exhaust Valve Oil Seals (P/N 21006516 - 1991-1994 LKO engines or P/N 21006515 -- 1995 L24 engines) |
• | Exhaust Valve (P/N 21007040) |
• | Start engine and increase engine speed to 3500 rpm. |
• | Hold engine rpm at 3500 rpm for approximately 30 seconds. |
• | Release accelerate, allowing engine to return to idle rpm and observe for engine miss or propping 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. |
P/N | Description | Quality |
---|---|---|
21008324 | Gasket Kit - Cylinder Head (91-94 LKO) | 1 |
21007332 | Gasket Kit - Cylinder Head (95 L24) | 1 |
21007040 | Valve - Exhaust | 4 |
21006516 | Seal - Valve Stem (91 -- 94 LKO) | 4 |
21006515 | Seal - Valve Stem (95 L24) | 4 |
21024468 | Wire Asm - Splg # 1 Cylinder | 1 |
21024469 | Wire Asm - Splg # 2 Cylinder | 1 |
21024470 | Wire Asm - Splg # 3 Cylinder | 1 |
21024471 | Wire Asm - Splg # 4 Cylinder | 1 |
16167763 | Coil Asm -- IGN | All Required |
To receive credit for this repair during the warranty coverage period, submit a claim through the Saturn Dealer System as follows:
Case Type | Description | Labor Operation Code | Time |
VW | Cut Exhaust Valve Guides | T9730 | 7.1 hrs |
Add: | A: With A/C | 0.5 hrs | |
B: With P/S | 0.3 hrs | ||
C: To install rocker cover gasket, if necessary | 0.3 hrs | ||
D: Misfire Diagnosis | 0.5 hrs |