Manufacturer communication — 2006 GMC YUKON DENALI XL

• Applies to GM passenger cars and trucks with gasoline engines only, model years 2000 to 2025.

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  Light/Medium Duty Trucks (including LCF MD) 2000 2025 — — Gasoline Engines Only

• Rough idle, crank no start, extended crank or misfire, with the engine warning lamp on and DTC P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 or P0308 set.

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  Information on Rough Idle, Crank No Start, Extended Crank or Misfire Due to Excessive Carbon on Top of Valves or Sticking Valves, Malfunction Indicator Light (MIL) Illuminated - DTC P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308 Set

• When the engine is cold, compression on multiple cylinders may be zero.

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  When the engine is cold, the compression on multiple cylinders may be at 0 kPa (0 psi).

• The engine may pop through the intake or exhaust while cranking, and the spark plugs may be fuel fouled.

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  The engine also may pop through the intake or exhaust while cranking and the spark plugs may be fuel-fouled when inspected.

Possible causes

• Major carbon build-up on the intake and/or exhaust valves from fuel contamination or incomplete burning of the fuel; misfires should not appear before at least 8,000 km (5,000 mi).

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  This condition may be caused by major carbon build-up on the intake and/or exhaust valves due to fuel contamination or incomplete burning of the fuel as shown below, so the misfires should not have appeared until accumulating at least 8,000 km (5,000 mi)

Repair

1. If there is no valve damage and no cam follower out of place, perform the cleaning procedure to free sticking valves and remove carbon from the valves and pistons.

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   If there is no sign of valve damage or cam followers that are out of place, perform the following procedure to free up sticking valves and to remove carbon from the valves and pistons.

2. If valves are damaged or cam followers are out of place, make the engine mechanical repairs first and then perform the cleaning procedure to prevent a return.

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   If valve damage is present or if there are cam followers that are out of place, perform engine mechanical repairs as necessary to correct the concern and then perform the procedure below to prevent the concern from returning.

3. Fill Cleaner Kit J-35800-A with about 650 ml (22 oz, 2 cans) of Air Intake, Combustion Chamber Cleaner and set the air pressure at the tool to 260 kPa (40 psi).

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   Fill Cleaner Kit J-35800-A with Air Intake, Combustion Chamber Cleaner, approximately 650 ml (22 oz-2 cans), and close the cap of the tool tightly. Set the air pressure to 260 kPa (40 psi) at the service tool.

4. With GDS 2 or a scan tool, command engine idle to 2000 rpm so the engine does not stall.

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   Using GDS 2 or a Scan Tool, command engine idle to 2000 rpm to prevent the engine from stalling.

5. With the engine at operating temperature in a well-ventilated area, slowly and carefully induce the cleaner into the engine, taking about 3 minutes.

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   In a well-ventilated area with the engine at operating temperature, slowly/carefully induce the Top Engine Cleaner into the engine, which should take approximately 3 minutes.

Parts

• The Top Engine Cleaning Kit (ACDelco Air Intake, Valve and Combustion Chamber Cleaner and ACDelco Fuel System Cleaner 44K) is 19435372 for the U.S. and Canada.

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  ACDelco Air Intake, Valve and Combustion Chamber Cleaner and ACDelco Fuel System Cleaner 44K (Top Engine Cleaning Kit) 19435372 (U.S. and Canada)

Caution

• Inducing too much cleaner at too low an RPM, or stalling the engine with too much cleaner at once, may hydro-lock the engine and bend a connecting rod.

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  If too much cleaner is induced at too low of an RPM, or if you force the engine to stall by inducing too much cleaner at once, the engine may hydro-lock and bend a connecting rod(s).