2011 Accord 2.4L AT – A friend’s car has a tricky issue.

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2011 Accord 2.4L AT – A friend’s car has a tricky issue.

2011 Accord 2.4L AT with 215K miles has two drivability issues, poor fuel economy, and throws P0171 & P0507 codes.

Issues:

Intermittent no start when hot
High/fluctuating idle 1,100–1,500 RPM
Repairs attempted:

New O2 sensor, coolant temp sensor, and MAF sensor
Vacuum hoses checked, fuel treatment added
New throttle body & PCV valve replaced—no effect
The car needs to pass smog in 6–8 weeks. Next steps: checking ECM connections and fuel pressure. Any ideas?

Moazzam asked on 12 Feb 2025 17:22:29 pm

1 Answer

29 views |

Waqas Rajput - on 12 Feb 2025 17:25:44 pm

AOA Brother!
These issues cant happen at the same time—if it won’t start, there’s no idle.

Does the high/fluctuating idle happen only on cold starts o r even when warmed up?
No-start when hot + erratic idle suggests a fuel pressure issue. Check with a fuel pressure gauge, especially on hot shutdown.
It could also be an ignition issue o r a vacuum leak P0171. Visual checks aren’t always enough—try using an unlit butane torch around intake/vacuum connections.
A failing fuel pump could cause pressure loss, leading to vapor lock. Try priming the fuel system by turning the key to run a few times before cranking.