For almost a year I have been struggling with a recurring problem that appears to be triggered by sustained driving on the highway. It has come up three times now and I thought I had it fixed after the second episode so I don't know what to try next.
It's a 99 Accord LX 4 door 4 cyl 5-speed, 184,500 miles (lots of highway driving).
The problem is after the engine hits operating temperature, it cannot idle at the bottom end -- when you slow down it just drops off to zero RPMs and dies unless you feed it gas with the clutch down. It first happened during an all-day drive last summer. I had just changed the oil, filter and air filter for the trip. To try to fix it, I replaced the spark plugs and the PCV, ran some injector cleaner through, and replaced the coolant and the ignition coil. That seemed to help a little and the car stopped dying so much but still ran uncertainly at low RPMs. Then I took another long drive (this time a warm day in December) and the same problem came back. This time I switched out the ignition wires, distributor cap and rotor. Lo and behold the car seemed almost back to normal. I have driven it up to 50 miles at a time without incident. But this weekend my son drove over an hour on the highway (warm abient temps, too) and sure enough, it started dying again.
There are no trouble codes being activated. I'm looking for a good idea on what to try next and this group is a great help. Thanks in advance for your suggestions.