Hope someone could give a good advice about my car's issue. I have a Honda Accord CL9 (2006, european) with 2.4 engine and manual transmission. The issue is that sometimes there is a sensible lack of power when you start moving or when you try to accelerate - it feels like car just choke and don't want to move forward. Also it jerks sometimes and makes a humming sound (like if you try to floor at near idle rpm, but in my case this happens when I start moving or accelerate from 2-2.5k rpm). When I change gears to higher ones - car's nose pecks (if that makes sense, sorry for my english) like if rpms are too low even if I release the clutch at the exactly correct rpms. Also it seems that air conditioning turned on makes it worse and more noticeable. One more symptom - I may hold acceleration pedal in one position while riding uphill and all of a sudden I feel that acceleration significantly slows down. I think this happens in the moment when cooling fans start working. But I doubt that air conditioning is the reason because I still can feel lack of power even with A/C turned off. It just becomes a little less noticeable and you don't feel this jerking while riding at the same speed. Fuel efficiency seems a little bit too low (~15% lower than it should be)
Mechanics in my city didn't help me with this issue (maybe due to lack of interest), they just attaching scanner tool, see that there are no errors or weird values from sensors and that's all, no one wants to dig deeper. And I personally don't have any knowledge and equipment to fix this.
Now what is interesting and to me the most important in this issue - is that it may disappear for a while if I detach battery for 15-20 minutes or if I change something which is affecting air-fuel mix (oxygen sensor, air filter etc). Usually after 100-200 km the issue returns back. This fact confuses me a lot because all possible issues which I can think of are mechanically related while this fact seems to exclude them (if something is wrong mechanically - how it can become normal for a while after disconnecting the battery? Makes no sense to me).
What I've already tried:
- Clutch changed.
- Accelerator pedal position sensor changed.
- Oxygen sensors (both) were changed.
- Air flow tube which goes from air filter to throttle valve changed (means no air leaks in it).
- Air filter changed.
- Fuel filters were changed.
- Throttle valve was cleared.
- Alternator was repaired.
- Driving belt + tensioner changed.
- Spark plugs changed pretty long ago (30-40k km) but they were new at the time when this problem appeared.
- Catalyst was replaced with downpipe by previous owner so it also can't cause issues.
- Engine is not overheating, thermostat is new and coolant fluid was replaced also.
- There is no brake shimming.
- Ignition coils have no visual damage.
The car has 210 thousand kilometers of mileage.
What are my assumptions:
- Knock sensor.
- MAP sensor.
- Fuel pump (but why it works well after battery disconnect? Makes no sense).
- Any weird electrical/ECU problem which I will never find.
Scan tools don't show any errors. The issue is not related to weather or any other logic. It is not related to style of driving. Sometimes car rides almost normally.
Any help and advice will be appreciated.