Manufacturer communication — 2006 GMC YUKON DENALI XL

• All brands and models, model years 2000 - 2017.

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  ALL ALL 2000 - 2017 ALL ALL ALL ALL

• MIL and/or engine misfire, rough idle, extended crank or crank no start; the misfire may be more apparent on a cold start, and it may count on one cylinder or several.

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  Some customers may complain of a MIL and/ or engine misfire, rough idle, extended crank, or crank no start in some cases, the misfire may be more apparent on a cold start and may run rough for up to 5 minutes after starting the engine, may count on a single cylinder or several cylinders, and may or may not be felt by the driver.

• One or more misfire codes (DTC P0300-P0308) are stored; SI diagnosis may not isolate the cause if the intake/exhaust valves are not sticking at the time.

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  Upon inspection, the technician will find one or more misfire codes (DTC P0300-P0308) stored in the ECM and SI diagnosis may or may not isolate the cause of the misfire depending on whether the intake/exhaust valves are sticking at the time of the diagnosis.

Possible causes

• Major carbon build up on the intake and/or exhaust valves from fuel contamination or incomplete burning of the fuel; the misfires should not appear before at least 5,000 miles (= 8,047 km).

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  This may be the result of 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 5,000 miles or more.

Steps to confirm (in the document’s order)

• With the engine cold, compression on multiple cylinders may be 0 PSI (= 0 kPa); the engine may pop through the intake or exhaust while cranking and the spark plugs may be fuel fouled.

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  When the engine is cold, the compression on multiple cylinders may be at 0 PSI. The engine also may pop through the intake or exhaust while cranking and the spark plugs may be fuel fouled when inspected.

Repair

1. If there is no valve damage and no cam follower out of place, perform the cleaning procedure to free the 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 valve damage is present or cam followers are out of place, make the engine mechanical repairs first and then perform the cleaning procedure to keep the concern from returning.

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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. With the engine at operating temperature, slowly induce a bottle of GM Upper Engine and Fuel Injection Cleaner into the engine with RPM held off idle enough to prevent stalling (typically around 2,000 RPM).

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   1. In a well ventilated area with the engine at operating temperature, slowly/carefully induce a bottle of GM Upper Engine and Fuel Injection Cleaner into the engine with RPM off of idle enough to prevent the engine from stalling (typically around 2,000 RPM or so).

4. Turn the engine off after inducing the cleaner and let it soak for 2.5 to 3 hours; do not soak longer than 3 hours because the remaining deposits may harden again.

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   2. Turn the engine off after inducing the cleaner and allow the cleaner to soak with the engine off for 2.5 to 3 hours (Do not let cleaner soak for more than 3 hours as remaining deposits may start to harden back up again).

5. To complete the repair, change the engine oil and filter and advise the customer to use only Top Tier gasoline to minimize future deposits.

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   6. To complete the repairs, change the engine oil and filter, and advise the customer to only use one of the Top Tier Gasolines listed at http://www.toptiergas.com and/or in the latest version of 04-06-04-047 (USA) or 05-06-04-022 (Canada) to minimize future deposits.

Parts

• Upper Engine and Fuel Injector Cleaner (16 oz, 473 ml) is P/N 88861803 (in Canada, P/N 88861804).

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  88861803 (In Canada, use P/N 88861804) Upper Engine and Fuel Injector Cleaner (16 oz, 473 ml) 1

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 a 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).