← Back to list

2007 Honda Civic Cold Weather Rough Idle with P0128 Code - Diagnosis and Fix

Model: 2007 Honda Civic Fault Code: P0128 Posted: 2016-02-01 16:40

I own a 2007 Honda Civic, and as soon as temperatures drop, my car begins to run roughly. The temperature gauge has also started behaving erratically, so I replaced the thermostat with an original Honda part. After the replacement, the engine runs poorly until it warms up—once warm, it runs smoothly without any engine light activation. However, a P0128 diagnostic code is consistently showing up. I'm seeking expert advice on how to resolve this issue effectively. The P0128 code indicates a thermostat-related problem, which may be contributing to the rough idle in cold weather. Given that my vehicle is experiencing these symptoms specifically during colder conditions, I believe there's an underlying cooling system or idle control issue worth investigating.

Related fault codes
P0128
Comments (2)
Anonymous 2016-02-01 19:55

Check reliable troubleshooting resources on this forum for common causes of P0128 and rough idling. Using a scan tool to monitor live data in real time will provide more accurate insights into the issue.

Anonymous 2016-03-01 00:01

Hey thenor, The 2007 Honda Civic is known for having sensitive idle behavior. Before performing an extensive diagnostic, consider two key fixes. First, inspect your coolant system—since you're seeing a P0128 code (indicating a thermostat issue), air bubbles in the cooling lines could be causing rough idling. Honda Civics are particularly prone to this problem. To resolve it: open the radiator cap and place a funnel into the opening. Fill the funnel with coolant and run the engine for 15 minutes while keeping the funnel full. This helps purge trapped air from the system. Afterward, shut off the engine, replace the radiator cap, and restart to see if the idle improves. Next, inspect your Idle Air Control (IAC) valve located on the throttle body. Remove it and clean the internal flap using carburetor cleaner. Ensure the valve is not stuck or obstructed. If it's stuck or malfunctioning, replacement may be necessary. Let me know how the fix turns out—this could help others with similar issues.