31 replies to this topic

[150DollarRacer]

I have never actually tuned a carb before. My dad is a car nut so I've been around them before and I am mechanically inclined so I don't think it will be too hard to do.

I looked at the online service manual for my civic and unless I read it wrong, I need to remove the carb to take out some screw on the bottom to allow to make mixture adjustments? Is that true?

When I bought the car it would never run cold unless one had their foot on the pedal. When it warmed up it would idle around 1500rpm but lope a bit. I washed down the carb with carb cleaner a couple weeks ago and that helped it idle around 800 or so but it still loped a lot.

This past weekend I pulled all the smog and EGR junk off and have installed block off plates so now its a matter of starting it again and getting it to run right I hope.

Will the carb need adjustting? I would assume so since it should be running leaner without the EGR in place.

Anyone have any tips for tuning?

[OldSkoolEX]

hmm..

mines not got any of the smog crap because im in the uk. mine runs fine but it idles like you say yours did.. all ive had to adjust on mine was the throttle cable and that prettymuch fixed the idling problem. spose you could try tweaking the throttle cable and maybe the amount of fuel thats injected and see if that does anything..

dunno about the screw on the bottom.. not had my carb off.

[vervepipes]

the screw's not on the bottom of the carb, it's on the top, after you've removed the air filter box. i need to find the appropriate mixture myself now that i've mada an open filter...

[HondaBoy]

Hey, This is exactly what i need to know! I need help adjusting my carb also. should i tune the mixture first, or the idle, or the chock opener, or the fule amount being put into or not into the carb. please help. I just replaced both of my filters fuel, and my car still sputters , do i need a new distributor cap and rotor, or fuel pump or what, god this sucks diong trial and error, but i guess i will know my car inside and out.

Eric

[OldSkoolEX]

thats what i like about carbs... no ecu to reprogram.. fiddle with a linkage or two, turn a couple bolts/screws and bingo..

[vervepipes]

first thing i did when i got my car over a year ago was i had the timing adjusted, that fixed my sputtering. then i went ahead and adjusted the gas pedal free play because it was too loose so while i was at it i adjusted the idle speed. i have yet to play with the mixture controls though, i've only adjusted once because i was way rich and needed to fix it fast, but i want to find the best mixture

[shauno]

First find out what carb you have.
Mine was a keihien I think.

What you have to do is this:

remove carb
turn it around so you can see the back,
look down towards the bottom of the back, you will see a little lead plug on the base plate of the carb, facing towards the firewall( if the carb was mounted)
take a drill bit about 1/8'' and drill a small hole in the plug,
get a screw and thread it into the hole tightly, now pull that biiaaatch out of the carb.
notice flathead screw inside the hole where plug was.
now install carb.
set timing
now adjust mixture by turning screw slowly, until car runs smooth.
don't go too lean.
you'll know lean once the engine starts to speed up noticeably.
once you get there go in a turn or two.
now set idle speed.
check timing again.
that should do it

If you want it perfect you can go to a shop and get them to put it on the scope for ten minutes.

[davens]

Can't knock the downdraft Webers...one screw for idle, one screw for mixture. Both easily reachable without removing anything.

Of course, if you start swapping jets and emulsion tubes it gets ugly quick.

[junk_scrvicHB]

i rebuilt my carb and now i just have a vacum prob. but all that will change will i fit my holly 500cfm 4-barrel . i have pics on it when im done with it

[150DollarRacer]

does anyone know what the stock carb is rated at? 500cfm seems rather large for 1.5L engine but i could be wrong.

[sdubfid]

stock carb is ~180cfm I believe?

[150DollarRacer]

So i started the car for the first time in two weeks and its running super rich. like raw gas coming out the exhaust. Should I expect it to run this rich after removing the smog controls or is it possible I hooked something up wrong?

[DarkHand]

So i started the car for the first time in two weeks and its running super rich. like raw gas coming out the exhaust. Should I expect it to run this rich after removing the smog controls or is it possible I hooked something up wrong?

The carb that came on my CRX was just as bad as that... When I removed it, there was about 1/2 a cup of gas sloshing around in the intake manifold... It was just getting WAY too much gas. As far as I know, I don't think an adjustment can fix something that bad, it needs to be rebuilt or replaced. I swapped the carb out and it ran great.

Edited by DarkHand, 13 April 2004 - 01:19 PM.

[150DollarRacer]

Ok, so i decided to take some pictures to show how I plugged the carb cuz maybe I just did something wrong. It wasnt running that rich prior. THats for sure.

The pictures are huge so that its easier to see.

First one:

http://www.engr.ucsb.....2293 copy.jpg

Connection A I hooked up to the intake manifold since I plan to remove the charcoal canister

Connection B I hooked up some nipple near the secondary throttle valve and connected it to the idle thingy on the right. Why? cuz I dont have any plugs so I figured this might work.

Connection C I just connected two ports on the manifold to keep them from leaking.

Second Picture:

http://www.engr.ucsb.....2290 copy.jpg

Connection A I loop the line together instead of using two plugs.
Connection B is for the lower nipple on the distrbutor and I connected it to a port on the front of the carb.

Connection C was mentioned in the first picture. This is the line from the other side that was suppose to go to charcoal canister but ended up here instead.

Third Picture:

http://www.engr.ucsb.....2292 copy.jpg

Connection A I looped to another open port on the right
Connection B I looped to Connection C
Connection D is two lines near the mixture screw. I looped them together. This is the only one Im not sure about since nobody has any pictures of this side of the carb.

Last picture for completeness:

http://www.engr.ucsb...ic/IM002291.JPG


Does anyone see anything odd or out of place? I took off the cap for the mixture adjustment to see if that made any difference. I turned the knob almost 2 clockwise rotations without any improvement. Somethings really wacky.

[DarkHand]

Connection A in the first picture looks to be the problem to me... Raw gas and gas fumes come out of the carb from that port, and you've got it going into the intake, which would send too much gas. Instead of routing that one to the intake, cap it off at the carb or leave it open. Make sure to cap the other side of the connection on the intake manifold side though, or you'll lose vacuum.