Guide: Fixing Rough Idle During Cold Start on Chevrolet

Make: Chevrolet | Model Example: 2016 Silverado | Avg. Mileage: 99705 | Job Number: 562614

Repair Issue:

Excessive Engine Carbon – Dirty Fuel Injectors

Customer Concern:

Rough idle upon cold start. Ok when warm/hot. The Engine Control Module (ECM) is setting Diagnostic Trouble Code (DTC) P050D.

Test/Procedure:

1. Run fuel injector cleaner through fuel system.

2. Run an intake type cleaner through intake manifold.

3. The above methods are an attempt to reduce the carbon that is known to build up on the intake and exhaust valves with a direct injected engine.

4. If same, remove spark plugs and use a bore scope to check for carbon in the cylinders. Look at the top of pistons and base of valves.

5. If the spark plugs are near 100,000 miles, replace them, retest cold.

6. Verify battery voltage upon start up. Should be 14 V or higher at cold start.

7. Have scan tool set up, start engine cold.

8. Watch misfire counters for each cylinder. Determine if misfire is on a cylinder or multiple cylinders.

Important Take-A-Way:

This archive directs a technician to a very common issue we’re seeing with Direct Injected engines with carbon buildup in the engines. With all of the advantages of Direct Injection, carbon buildup is one of the disadvantages and something that will likely become routine maintenance in the future – another benefit for shops that do maintenance services.

Most Popular Fix:

Performed Engine Carbon Cleaning Procedure or Replaced/Cleaned Fuel Injector(s)

Other Common Car Problems:

View more common car problems from the most popular manufactures including Ford, Dodge, Chevrolet, Honda, Toyota, and more. Read more

Also Applies to the Following Makes and Models:

2014 Verano 2.4, 2016 Colorado 3.6, 2013 Equinox 3.6, 2014 Silverado 1500 5.3, 2015 Silverado 1500 5.3, 2016 Silverado 1500 5.3, 2017 Silverado 1500 5.3, 2018 Silverado 1500 5.3, 2015 Suburban 5.3, 2016 Suburban 5.3, 2015 Tahoe 5.3, 2016 Tahoe 5.3, 2017 Tahoe 5.3, 2014 Savana 1500 5.3, 2014 Sierra 1500 5.3, 2014 Yukon 5.3, 2016 Yukon XL 5.3, 2016 Yukon XL 6.2, 2014 Yukon XL 1500 5.3

Author: Bill Siegmann

Bill’s automotive diagnostic experience began in 1985 at a Buick dealership. He is a certified ASE Master and L1 technician with 33 years of diagnostic experience. Bill has 13 years of Buick experience and is a certified Buick Service Master Tech. Outside of work, he enjoys outdoor activities: camping, hiking, canoeing and kayaking. He also enjoys traveling and visiting new places. Closer to home, Bill likes to cruise around in his 1968 Camaro convertible, weather permitting.

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