2000 honda accord lx 5 speed manual f23a4 motor 141,xxx miles. I posted before about the same issue but its still going on and i figured rather than bring back an old thread, i'd make a new one. I cleaned out the IACV but the car still idles rough with vibration in the steering wheel after its warmed up but only when I have the lights, rear defrost, ac, etc. on. I figured what the hell and filled up the tank with 93 octane instead of 87 and the problem is still there but is much better. any ideas?

 

Have you done a tune up recently, cap, rotor, plugs?

Changed the fuel filter?

Ever check the timing?

 

sorry about the novel haha. had the cap and rotor checked when i had the alternator replaced about 11 months ago. They were fine. Had the spark plug wires checked at the same time. They all were fine. Spark plugs were replaced at the same time as the alternator. Havent done anything to the fuel system. Never checked the timing but a new timing belt and water pump are towards the top of the to-do list. I havent done anything tune up related other than what was mentioned above. After doing some research on causes i found that it could be any combo of 25 different things so im just looking for some suggestions on what is more common.

 

Have you pulled the codes/Are there codes? Most of the large chain parts houses will let you use an OBD-II scanner. Hook it up and see what the computer sees. If there are no codes, then it is mechanical and not sensor related.

Does it idle rough and stall or does the tach move up and down between 800 and say 1500? When it goes hot (summer day or parked in the sun) is it worse or hard/no start? If so, you may have a main relay going out. Common on older hondas but not as familiar with 2000 models.

The reason for this is the Main Relay supplies the juice to your fuel pump. Fluctuation in current can cause an off/on fluter in the pump that causes decreased fuel pressure. One an injector falls below a certain pressure, it will not fire. So your car now will run like and old "hit and miss" engine. The heat in the passenger cabin expands the solder joints in the relay and causes havoc with the fuel pressure. I have seen the symptoms you describe in an early stage failure of a main relay.

If you don't have codes, pull the main relay. Inspect for bad solder joints. There is a ton of information on Honda relays on the web. If you are looking for the most likely cause, that would be my first guess.

 

You made interesting point it idles rough under load. I would test the charging system as well, 14.1 volts running and 12 volts with key on. simple do that first.

Another thing when you turn on these items what is the rpms? are they low and then is runs rough?

By the way if you have never done it, do the fuel filter, can't hurt it is time for it.

 

have you tried seafoam or b12?

 

alright, so the alternator and spark plugs were replaced less than a year ago. the wires from the distributor cap to the individual plugs were brand new when i bought the car in december 2010. havent checked out the distributor cap and rotor yet but thats one thing i suspected so im gonna look into that at the first chance i get. when the rough idle first developed, my headlights would dim any time the ac compressor kicked in so i went by advanced auto parts and had them check out the charging system. it turned out that the battery was bad but everything else was ok so i got a new battery. no more dimming headlights but still a rough idle. the idle doesnt fluctuate, and its pretty close to spec according to my haynes repair manual (maybe a tiny bit above), and the rpms dont drop any that i can see or hear when i turn stuff on, the engine sound is just a deeper pitch and i can feel vibrations. This problem has never caused me to stall. I havent changed the fuel filter, but thats one of the things i plan on doing soon. regardless of temperature it still starts right up in the first twist of the key but after cold nights (like we've been having recently in new england) it starts a little rougher but no where near enough to make you scratch your head. as far as i know there are no error codes but i couldn't be sure because i've never checked it with a computer, but the check engine light has never come on. now, i have a question or two to ask. could there be error codes if the check engine light isnt on? if the main relay is bad, is this something you just buy a new one and replace it or does it need to be taken apart to be repaired? is this something that a problem with the electronic load detector could cause?