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Can someone tell me the function of screw set #1 on throttle body for a '99 Accord, 2.3L and how and when it should be adjusted? Unless of course it's not to be adjusted.
Someone correct me if I'm wrong but generally, throttle body adjustment screws are not to be adjusted on Hondas - they're set at the factory and not intended to be changed. If you're having idle issues, I'd start checking other things first...
It should never be adjusted but if someone did, you will do as follows. Warm the car completely up and turn it off. With car off, unplug the iacv connector. Then star the car up and the car should idle at 500 +- 50 rpms. It will act like it's going to stall, this is normal. You will turn that screw in or out to get it in that range. Keep in mind the first big line after 0 is 500 not 200. Each small line after 500 is 100 until the 1000 mark. After you have it at 500 +- 50 rpms(ideally you'd probably want 600), turn the car off. Remove the radio/back up fuse in the engine bay fuse assembly for about a minute. Plug it back in. Let the car completely cool down. After about 2 hours, start the car up without touching any accessories or turning anything on. Let it idle until the fans come on. You're done doing idle relearn.
Someone correct me if I'm wrong but generally, throttle body adjustment screws are not to be adjusted on Hondas - they're set at the factory and not intended to be changed. If you're having idle issues, I'd start checking other things first...
Mostly correct. On Fuel injected cars it's usually the Idle STOP screw that is to never be adjusted. This is set at the factory and is never to be adjusted. If it needs adjustment, usually there is something mechanically wrong with the throttle body shaft or blade.
However, on higher mileage vehicles the idle adjusting screw, or some call it the CO screw, tip can become coked up or the O-ring damaged which will affect idle and idle quality.
What I have done in the past on other makes when the idle is not quite correct and all other components have checked out, is to remove that screw and count it down to the correct turns. Usually mark the housing and the screwdriver so I can easily count. Verify the screw is not coked up or the passage is clogged, clean it if need be, and then reinstall the screw the same amount of turns. Hopefully no one has goofed with it before me, and the idle returns to normal.
If not then the proper adjustment needs to be done to baseline the idle.
Thanks Mike for the info. I removed and cleaned the TB over the weekend and the engine seems more responsive. I'm still having hesitation and RPM dropping at low speeds from a stop. The engine returns to normal after driving less than 1/4 mile. Once the almost stalling episode is over both the idle is straight on steady and the acceleration is normal on long or short trips. There are no codes. Do you think the idle adjustment screw might be causing the rough starts? It's never been adjusted with 240000 miles. I'd like to check it out and change the o-ring.
In your reply you said to count down the turns. Are you saying I should turn the screw down till it stops - counting turns along the way and then backing out the new screw an equal number of turns? Seems obvious but want to be sure before I attempt.
In your reply you said to count down the turns. Are you saying I should turn the screw down till it stops - counting turns along the way and then backing out the new screw an equal number of turns? Seems obvious but want to be sure before I attempt.
Remove the screw and count the number of turns it takes to remove the screw, you will feel the threads 'click' when it has come to the end of the threads. Pull out the screw and clean the needle tip as well as the port in the TB.
I would not screw it in, as there my be a build up of carbon that may damage the threads of the screw or bore hole by impacting the carbon by tightening the screw. Also if there is a lot of carbon when you screw it in, you may not fully seat the tip and just impact the soot. This would give you a falst number of turns to bottom out the screw.
Remove the screw.
Note the amount of turns (e.g 5-1/3 turns).
Clean screw tip and passage of soot and carbon.
Reinstall screw the same amount of turns you removed it.
Reinstall TB, and verify the idle is correct.
05-24-2015, 07:57 PM
Throttle body screw function?
