Fix P050D: Mechanic’s solutions that WORKED

The code P050D: Cold Start Rough Idle signifies a rough idle during cold starts, pointing to potential issues in the fuel or ignition system, or even imprecise engine timing. This can result in a suboptimal performance that’s especially noticeable when the engine hasn’t reached its optimal operating temperature.

P050D quick overview

Meaning	P050D: Cold Start Rough Idle
Is it serious?	Yes, it may indicate issues affecting the vehicle’s performance and fuel efficiency.
Possible causes	– Dirty or faulty fuel injectors – Low fuel pressure – Vacuum leaks – Faulty ignition coils or spark plugs – Inadequate engine compression – Incorrect fuel mixture – Malfunctioning sensors (MAF, MAP, coolant temperature, etc.) – Engine timing issues
How to diagnose?	Read OBD-II Codes: Gather detailed information using a diagnostic scanner. Visual Inspection: Check for any obvious signs of damage or leaks. Inspect Fuel System: Evaluate fuel pressure and injector operation. Check Ignition System: Examine the condition of spark plugs and ignition coils. Search for Vacuum Leaks: Use a smoke machine or similar method. Conduct Compression Test: Assess the compression level of each cylinder. Analyze Sensor Data: Review readings from MAF, MAP, and coolant temperature sensors. Verify Engine Timing: Ensure timing is set correctly according to manufacturer specifications.

How to fix P050D – learn from mechanics

I looked into P050D service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Chevrolet

Vehicle Information 2014 Chevrolet Silverado 1500 LT, 5.3L

Issue + Repair History

• MIL (Malfunction Indicator Lamp) on
• Misfire on cylinder #6, tapping noise detected
• Replaced lifters on #4 & #6, camshaft, head gasket, timing chain, oil pump, and fuel pump push rod
• Knocking noise in the intake after repairs

Other OBD2 Codes + Test Results

• P0300: Random misfire
• P050D: Cold start rough idle (indicates an injector issue)

What Are People Suggesting to Fix the Issue

• Replace the VLOM (Valley Cover or Lifter Oil Manifold)
• Check for cylinder with no exhaust action, possibly due to an exhaust valve not opening
• Check if the bee-hive coil spring is broken, causing exhaust reversion
• Inspect valves on cylinder #6 for worn cam lobes, bent push rods, or broken springs
• Verify if lifter is installed correctly; it could be 180 degrees out on the exhaust valve
• Check for restricted passages in the VLOM, preventing lifters from collapsing and opening

Final Fix

• Customer traded in the truck; further details were not provided.

Case #2: Chevrolet

Vehicle Information
2017 Chevrolet Silverado 1500 LTZ, 5.3L engine

Issue + Repair History

• Rough idle on cold start lasting about 15 seconds
• Code P050D (Cold Start Rough Idle)
• Misfires, especially on cylinders 7 and 8
• Various tests performed (injector balance, compression, vacuum waveform)
• No significant changes after adding fuel additive and swapping spark plugs

What Are People Suggesting to Fix Issue

• Replace restricted injectors, using VIN to order correct parts
• Check for fuel pressure drain back overnight
• Investigate potential exhaust restriction
• Review TSB for coolant intrusion at intake to head seals
• Inspect lifters for bleeding down and oil pressure issues
• Scope ignition and injector patterns; Ohm coils and injectors

Final Fix

• The final fix was not mentioned as the help request was automatically closed due to exceeding the time limit without an update.

Case #3: Chevrolet

Issue + Repair History

• Codes: P0300 (misfire), P050D (cold start rough), P219B (fuel trim bank two)
• Misfires reported
• Fuel pressure tested and found to be good
• Carbon cleaning service done

Other OBD2 Codes + Test Results

• No additional test results mentioned

What Are People Suggesting to Fix Issue

• Check Active Fuel Management (AFM) system
• Monitor misfire counters and freeze frame data
• Inspect for rust/debris in fuel rail
• Check fuel trims and alcohol composition percentage
• Perform injector afit test
• Review oxygen sensor function and alcohol composition
• Inspect for carbon buildup on intake valves
• Check for injector leakage
• Use top tier gas and consider injector cleaner
• Replace faulty injector(s) after identifying misfiring cylinders

Final Fix

• Replaced the four injectors on the passenger bank with AC Delco injectors
• Road tested and completed all monitors, issue resolved

Case #4: Chevrolet

Vehicle Information
2014 Chevrolet Silverado 1500 LT, 5.3L engine

Issue + Repair History

• Persistent misfire on cylinder #3 after sitting overnight or for a couple of hours.
• Previous repairs: Fuel injector on #3 cylinder replaced, intake valves cleaned, coils and plugs swapped.
• MIL: Yes
• Codes: P0300 (misfire)

Suggestions to Fix Issue

• Check injector driver.
• Use a scope to check secondary waveform and current ramps for injectors and coils.
• Conduct a running compression test.
• Check for intake vacuum leaks with smoke machine or water method.
• Perform a crank relearn.
• Check for coolant leaks with pressure testing.
• Swap spark plug on cylinder #3 and look for coolant telltales.
• Listen to injector #3 with a stethoscope for inconsistencies.

Final Fix

• After ruling out coolant, compression, fuel, and spark, a GDI cleaning kit was run through the system. The misfire persisted but improved. The vehicle was to be taken on a trip or traded in, so the final resolution was pending further information.

Advice	Diagnostic Step Description
Check Fuel Injectors	Inspect injectors for proper function, swap or replace if necessary.
Examine Spark Plugs and Coils	Swap coils and plugs to see if the misfire follows; check for cracks.
Perform Compression Test	Ensure each cylinder has adequate and consistent compression.
Conduct Leak-Down Test	Test for cylinder leakage which might indicate internal engine issues.
Inspect Intake System for Vacuum Leaks	Use a smoke machine or water method to reveal any leaks.
Utilize Diagnostic Tools	Use an oscilloscope or similar tool to assess injector and coil waveforms.
Consider Engine Mechanical Issues	Examine the valvetrain and other mechanical components for faults.
Check Coolant System	Look for signs of coolant leakage or head gasket issues.
Run GDI Cleaning if Applicable	Clean the fuel system, especially in Gasoline Direct Injection engines.
Conduct a Crank Relearn	Relearn the crank position to ensure accurate ignition timing.