Yesterday my 2005 Honda Accord was running at a low idle when cold and stalling out when warm. Today I resolved the issue but I'm not sure what exactly I did that resolved it or what the original cause was. I'm looking for advice on what the cause could have been and what else I should investigate to prevent the issue from occurring again.
- At cold start engine was idling very low, around 500.
- Once vehicle was at temperature the idle would drop further and the vehicle would stall out if I didn't keep the idle up w/ the accelerator.
- No check engine light.
Troubleshooting steps performed:
- Suspected poor air-flow. I removed and inspected the air filter. Air filter was fine. Started car with air intake open (air filter removed) and no change in behavior.
- Suspected poor battery or poor battery connection. I disconnected the battery, cleaned and lubricated the terminals, topped off battery with water, reconnected. No change in behavior.
- Suspected bad Mass Airflow Sensor. Disconnected MAF electrical, restarted motor. No change in behavior.
- Suspected engine controller needed reset. Disconnected battery, reconnected, held motor at 3000RPM for a minute. No change in behavior.
- Suspected bad gas / water in gas tank. Added 1 gal fresh fuel. Fuel gauge at 1/4. Added 1/4 bottle methyl alcohol fuel dryer (HEET). Ran motor at 3000 RPM for a minute. No change in behavior.
- Let vehicle sit overnight. Tested vehicle the next morning, 3000 RPM, no change in behavior.
- Suspected coolant system might have air in it (and this would be impeding operation of the Idle Air Control Valve IACV?). I removed the cap to the coolant reservoir and lifted the tube so I could observe coolant overflowing into the reservoir. I turned off the cabin fan and moved the heat to high, started the engine and held the idle at 2000 until the engine was warm. The coolant reservoir was just under MAX when the engine was warm. No change in behavior; engine still stalled when warm.
- Suspected stuck IACV. At the advice of Eric The Car Guy (see below) tapped IACV with back of screw driver while revving engine. No change in behavior.
- Suspected bad Throttle Position Sensor (TPS). Disconnected TPS electrical, restarted engine. Idle was fine! Check engine light now on.
- Shut engine off, reconnected TPS, restarted engine. Idle was fine. Check engine light still on.
- Took car to gas station, filled it with gas, on the way back check engine light went off. Low idle is still rough and acceleration is a little hesitant but it no longer stalls.
Would appreciate suggestions on what the cause could have been and what (if anything) I should look at next. Thanks!
Update: Never found root cause of this issue, but now I have a new one. See 2005 Honda Accord 4cyl revving idle when warm