Your 2021 Compass runs rough during cold starts with P0507 indicating high idle issues. Cold starts demand more from the engine, and idle control problems become most apparent when the engine is fighting to warm up.
Why Cold Idle Is Challenging
Cold engines require:
- Higher idle RPM for stability
- Richer fuel mixture
- More ignition advance
- As the engine warms, these requirements change
P0507 indicates the idle is higher than commanded—but rough idle suggests the system is hunting, trying to stabilize.
What P0507 Means
The P0507 code indicates "Idle Control System RPM Higher Than Expected." The computer commands a specific idle speed, but actual RPM exceeds it. The constant adjustment creates the rough feeling.
Cold-Specific Causes
- Vacuum leak - More apparent when engine cold
- Carbon on throttle body - Affects cold idle air bypass
- Coolant temp sensor - Wrong reading affects fuel/timing
- IAC passage blocked - Can't regulate cold idle air
General P0507 Causes
- Throttle body carbon - Most common
- Vacuum leak - Common cause
- PCV valve stuck - Adds unmeasured air
- Throttle body fault - Motor or sensor issue
Diagnostic Steps
- Inspect throttle body for carbon
- Check for vacuum leaks
- Verify coolant temp sensor reading matches actual temp
- Monitor idle RPM vs commanded
- Check IAC passages for blockage
Throttle Body Cleaning
Often the first and most effective fix:
- Remove intake tube
- Spray throttle cleaner on plate and bore
- Wipe clean
- Reassemble
- Perform idle relearn
Repair Costs
- Throttle body cleaning: $100-$200
- Coolant temp sensor: $75-$200
- Vacuum leak repair: $100-$300
- Throttle body: $400-$800