2000 Accord LX - engine struggles when mildly warm
 

I have a weird problem - I suppose not weird for those who know more about cars :)

My normal usage pattern is drive (to work) for <10-min (~1.5 miles), again drive for <10-min for lunch in about ~2 hrs, return from lunch in ~1 hr (again drive of <10 min), eventually return back home after 4-5 hrs. Car starts up fine at all times except for that return trip after lunch which is when engine starts but struggles to get into normal rhythm. Today lunch stop was shorter around ~45-min and it started up and stopped and then on next start it went to usual pattern of struggle to get into rhythm and then be ok. I have not experienced this anytime when I have driven longer distance or stopped for a very short time.

Car has Check Engine Light on all the time for last 4-5 yrs. Code read out is P1486 - cooling system malfunction. Mechanics have tried replacing thermostat & temperature sensor at one time, changing some gasket at another time - they do the work, turn off the light, it stays of for 2-3 days and then comes back on. (Which is partly why I am asking here instead of taking it to a mechanic yet).

Other issue, I don't know if related is, when car starts up and is idling I hear hissing sound as if some air is leaking seemingly from under steering - but I don't feel any air coming into passenger cabin from anywhere. The sound goes away when I get out of parking gear. This started happening at the same time as engine struggle issue. Both of these things seem to have started after I had gotten rear-ended last summer & got things fixed. Damage was cosmetic and to rear side but California required inspection so I had to get check engine light fixed - that was when thermostat/temperature sensor was replaced.

Any suggestions on what I can try?

When the engine is cold, turn the key to the II position, but do not try to start the car. Make sure the a/c is switched off. Open the hood and let us know if the radiator fans are running.

Also, is this a 4-cylinder or a V6 accord?

Thanks. I tried that and radiator fans were not running with engine cold & key at II position.

It is 4-cylinder accord.

Hissing sound usually means a vacuum leak. If it's automatic transmission, the rear engine mount (down low between engine & firewall) is vacuum-operated. There's a plastic canister down there somewhere to "store" vacuum for that system. Look for disconnected vacuum hoses, and/or maybe that plastic canister is cracked. But a vacuum leak would normally cause problems running, not just warm-starting. Things like surging idle.

Another (less likely) thing is an injector leaking down after you shut off. (But it won't explain the vacuum-leak sound.) Injector leaks fuel & nearly floods the engine when you restart. If you wait a few hours that fuel evaporates & it starts pretty normally.

I guess hissing sound could be unrelated. It is automatic transmission. This is mostly unrelated to current problem but car does struggle to shift gears occasionally. I had that looked 4-5 yrs ago and mechanic said only solution is to change transmission but he won't recommend spending that much given age/value of car. Car has 104k miles now. I haven't gotten major maintenance like timing belt or water pump replaced - tbh I haven't taken good care of the car - I've been doing only ~4k mile/year last 7-8 years so oil change frequency is down to ~once a year, only other maintenance has been coolant/engine flush occasionally.

Given your mileage, or lack of it, I'd do a timing belt and water pump change. I'd also do the balance shaft belt too, since you'd have that end of the engine exposed. I only say that, because the original timing belt is supposed to be changed at 7 years or 100K miles. After that the belt is supposed to be changed every 6 years and 60K miles. Right now your belts are 19 years old, and should be getting changed for a 3rd time due to age, not mileage.

Your mechanic might not think so, but these engines are "interference" engines. My wife's 2000 Accord sedan LX got a replacement belt at 217K miles when we got the car. The water pump was leaking (Honda brand pump), so that was the time to do it all while I was in there (I'm my own mechanic). That car now has 239K miles on it 5 years later, and we take on cross country road trips. This means there's a lot of life left in your own car, with it only having 104K miles on it. With such low miles, I'd probably do a 3+3 trans fluid swap (drain 3 quarts, refill it, run it, then do it again 2 more times) and maybe even a tune up (cap rotor, plugs), as those things never hurt how it runs.
I know none of the things I mentioned directly go to your problem, but they are probably needed.

Yes, will get those done, intention has been there but keeps getting pushed off.

@PAhonda any suggestions? I have no clue if radiator fans were supposed to start with key at II position but as I wrote they didn't.

@JimBlake should I try getting fuel injector service? Hopefully they clean up and replace o-rings or fuel injector itself if needed. Your description of what would happen with leaking fuel injector matches what I am seeing. The hissing sound is always there at start but engine struggling to start happens only when engine has been off for 45min-1.5hr those I guess are unrelated issues.

The fans should not have turned on during that test.

The diagnostics for a P1486.

Step 1, when the engine is cold, remove radiator cap and check coolant level. Do you have to add coolant?
Step 2, do that fan test described in my first post. It passed the test.
Step 3, replace thermostat. You already did this.

That is the end of the testing procedure.

Stop by a parts store and have them scan for codes again. Just want to make sure there are no new additional codes.

There is an interesting note in the shop manual that says opening the hood can trigger a P1486. Not sure why yet.

Do you recall any work done on your car before this issue started?