Air/Fuel Mixture Screw? Where?

... Alright. I don't know if I trust the dash tachometer but if I assumed it was close then I'm idling at 1.4k-1.5k rpm (after all adjustments I could do). I'm not concerned because of the tachometer but because it does idle a bit higher than my other 88 LX. I tried to remedy it by popping off the filter housing and making sure the cable deflection is good (also because it was staying higher at stop lights and signs - fixed). I also adjusted the throttle stop screw until it wasnt even touching the lever. After this I figured it was getting too much fuel so I wanted to adjust the air/fuel mixture via that screw I saw on the pictures here. I stick my screwdriver there and get nothing. So I grab a mirror to see inside and lo and behold it is plain silver inside the hole. No slot no nothing. Either I'm a lamer or this is indeed a POS carb :banghead: . How is this possible? There's gotta be a way to adjust this somewhere. Help appreciated (sorry for the winding talk).

visit my website (in the keihin carb tech section). I have some pics of the airfuel mix screw being added as I type.

also did you try adjusting the diaphragm on the left side?
If you have a vacuum leak to that diapragm, then the idle will raise since theres not enough vacuum to hold the srew off the throttle.

some times the A/C booster get stuck ! that's why it idles high ! or may be the throttle cable is stuck !
and about the Mixture screw may be it 's covered with something

check the Faqs !

MIKE

did the carb run fine before it started idling fast?
i don't think it is your mixture screw. don't touch it unless you know what are you gonna do exactly.
Accord Ex may be right check your throttle cable, any linkages that can keep eather choke or throttle plate open.
if everything seems normal, than just drop RPM wih idle screw. eventially it will come back to normal idle and you just have to raise it to normal.
but don't mess with mixture screw if you live in a state where you need to pass emissions.

I guess I missed mo history, ma bad. I got the car a month ago and it had idle flactuations, which I was told about. Mostly happened when not warmed up. After figuring it wasnt the sensors I checked the PCV valve and replaced it coz it was the cheapest thing I thought might be related. Guess what? Flactuations were fixed! Now it shoots straight to 2.5k - 2.8k fast idle after a split second delay, then drops down to 2k after about 3 mins, then I lose patience and drive after a couple. As ad lib I changed spark plugs, both fuel filters, air filter, crankcase breather filter, hosed the black gunk from the carb with carb and choke cleaner, and adjusted the stick throtle cable. It idled pretty smooth except I felt it was a little high. Otherwise on the highway its a stallion. Economy is about 27-29.9 on 87 octane with 25miles highway + 4 miles stop 'n go per day.

What really started getting to me is that there conditions where if I let off the gas the car jerks as it kicks into idle mode (assuming it senses that) and accelerates for that short period of time. Another thing I thought might be related is that when I step on the throttle from shifting up or down between 1 and 3 it seems it get fuel ok for half a second, dips a little, then comes back up full power again. I just hate riding the clutch 1 sec longer to smooth that out. That may also be the tranny too I guess. My conclusion was that there is a fuel ripple somewhere there.

I looked at the spark plugs (2 of em) and they dont seem to be sooty from running rich at all but maybe the highway cleans them up at 75-80 mph. I will check the other adjustments and leave the mixture screw alone. I have verified the location, it just seems to be covered. I'm still happy with the car even if I cant bring the idle down. The FAQ here has all that propane addendum that I just couldnt do. I've also gone through the threads here. For peace of mind I will ask some shop to measure the rpm for me with more precise equipment. Besides, the previous owner says he's never messed with the carb at all and the car has 226K miles on it.

Thanks for your suggestions guys. Do add if you have more to say.

yeap, sounds like your car has the same problems. idle flactuations, rmp drop when turn on the lights or push the brake pedal.
i am blaming vacuum crap we have under the hood.
i am gonna take it off when i have a free time probably sometimes in the spring.
if you live in a state where you don't have to go through emission test, get rid of the vacuum crap.
A20A1 has very good pictures what you will need do to the carb.
what to plug and what to leave for a few vacuum lines.

I need to find a way to fix the #1 drawback to the mechanical secondary... and that is the lack of fuel to compensate for the fast opening of the secondary.


As for the vacuum line removal... you may lose some functions like Cruise control and MPG and Emissions will suffer slightly.

Since I dont do long uninhabited highway commutes I do not use cruise. Actually I hate the whole slow down <- > speed up cycle and when somebody cuts you off right when it guns the engine. We dont do emission tests here and whats a little MPG drop since I have to warm up the car in the winter at 0-30 F.

Hey A20A1, are you saying the mechanical secondary is responsible for that jerk/ fuel ripple when I come off and on the throttle? I need a good carb technology book.

- mindlos

You may have a loose venturi or more than likely a vacuum leak.

Aslo fuel filters will cause the car to have slower acceleration