AccordCoupe

I've got a troubleshooting question for you seasoned pros out there. I sold my 2000 Accord to my brother a few months back when I got my Si and now he's been having some intermittent starting trouble. My Helm manual went with the car and he's not very experienced with vehicle maintenance or troubleshooting. We're meeting up for a family member's graduation this week and I'm going to try to figure out where the trouble is coming from as well as do some preventative maintenance since he's just past 100k mi.

I had the car since new and NEVER had any sort of issue starting it. I live in the very dry Mojave Desert and the car spent it's last 6 years there. My brother lives in Davis, CA where the climate is much more humid and it rains a lot more. Other than that I can't think of anything that's really changed. Mods that could affect engine operation are an AEM CAI with K&N (I may advise he swap this if an oil analysis I'm going to do shows too much dirt ingestion) , DC Sports header, AEM alternator and power steering pulleys. Plugs are NGK Iridium and have probably been in for 20k mi. Cap and rotor as well as wires are OEM and we plan on replacing these this Thursday-Friday as well as a visual inspection on the timing belt (short block was replaced by Honda at 50k mi which means a new timing belt should have been installed but we want to make sure it's wearing well).

Below is his description of the problem.

"For the past four months the car won't start once every 2-3 weeks, this is usually after 2-4 days of inactivity. The car will start and then act as if stalling out and die within 2-3 seconds of starting. After this point I am unable to restart the car, and it sounds as if it is unable to turnover. I have tried then checking the battery level which is at lowest 11.4-11.5 V after cranking for a while but usually at 12.0 V. I have tried resetting the kill switch, resetting the key in the ignition, turning off all electronics, and starting in gear or in neutral. Nothing I have found to make any difference. If I try starting the car the next day or later in the day there is no problems. While running the battery reads ~14.2 V. No computer codes have shown at any point during any of the problems. The maintenance required light is on but it is due for an oil change. Just yesterday I had the car not start after four hours of inactivity. I left the car for five minutes and then it started right up. I cannot visibly finding anything wrong and the mechanic I took it to could not get the problem to occur but also could not find any problems."

Any suggestions are greatly appreciated as your advice will help me start looking in the most obvious places first and make the most of the limited time we'll have to work on this. I'm fairly experienced in working on this car but not experienced enough to be able to remotely troubleshoot it with someone that's not very familiar with cars (He's a third year vet school student so I've got to cut him some slack for not being as mechanically inclined as his older brother!)