my 4af carb worse gas mileage - Toyota Nation Forum : Toyota Car and Truck Forums

lgene10 · 10-26-2010, 09:30 AM

hi.. my car eat a lot of gas... my car just being overhaul after sitting for 1 yr the engine was successfully overhaul and we clean the carb and rebuilt it.. but there's a problem on my carb my engine doesn't idl so good it idl around 700-1400 sometimes 500.. fuel consumption 2km per liter... this is insane!..

90 GP · 10-26-2010, 09:56 AM

So did you ever replace the aap diaphram as suggested?

lgene10 · 10-26-2010, 09:50 PM

yeah... and i replace a few vacuum hose sometimes the idl is good 800 rpm.. sometimes bad... and the engine still eat a lot of gas.. the gas mileage should be 10 - 12km per liter... should i replace the whole carb?

90 GP · 10-27-2010, 06:40 AM

Did you check the carb float level? There is a clear plastic sight glass on the side that lets you see the fuel level. The fuel level should read in the middle of the sight glass. If it is higher the float may need adjusting. Also if any hoses going to the throttle positioner ( on same side as sight glass) are leaking can cause that fluctuation in idle speed.

lgene10 · 11-04-2010, 09:35 AM

ohh there's a leak from aap... so i sealed it for a while. i couldn't fine replacement in our town... mechanic told me that the aap purpose is for starting.. but the engine start fine.. BTW the idle speed now is on normal 800 good news^^ i replace some vacuum hose.. but when i stepping the gas pedal quickly the engine seems to be lugging a little.. but when im stepping the gas gently its seems to be fine... and the throttle positioner.. the circle thing.. my father try to adjust it but nothing happen.. aap broken, and now that positioner thing -_-

Donald · 11-04-2010, 07:09 PM

Quote:

Originally Posted by lgene10

but when i stepping the gas pedal quickly the engine seems to be lugging a little.. but when im stepping the gas gently its seems to be fine...

That is bacause the AAP (auxillary accellerator pump) is not working.

Trying to drive hard with it plugged off could possibly hurt your milage.

lgene10 · 11-07-2010, 08:41 AM

oh one thing... when im turning the headlight on or fog light the idle seems to be slowing 800 down to 500

90 GP · 11-07-2010, 08:54 AM

The dual diaphram throttle positioner isn't set correctly. When a load is placed on engine the throttle positioner adjusts idle to compensate. Get a manual and adjust it. There are two set screws.

lgene10 · 11-07-2010, 10:32 AM

yeah i forgot about that... do you mean dual diaphram throttle positioner? i can only see 1 diaphram throttle positioner.. i search for 4af carb i can see 2 throttle positioner.. do you think im missing 1?...

90 GP · 11-07-2010, 11:56 AM

It's on passenger side of carb right next to clear sight glass. Has at least two vac hoses going to it and I believe two set screws. The manual gives details on how to set it. One setting is for the idle up with load (lights) other setting is for decelearating to hold open throttle slightly .

lgene10 · 11-07-2010, 06:52 PM

it's a bit weird... there are only 1 vac hose going to it..
here some pic of my carb...

http://s1231.photobucket.com/albums/...Photo-0123.jpg

lgene10 · 11-07-2010, 08:02 PM

i know there are 2 adjustable screw with spring... but i can only see one

lgene10 · 11-07-2010, 08:08 PM

do you think there's something wrong with my carb?

90 GP · 11-08-2010, 05:09 AM

I looked at my pic and it's a dual diaphram here in the U.S version. Assume yours only is for idle up under load and not also for deceleration. To check it have someone start it ,turn on lights or other load while you watch to see which cam of the positioner moves. That is the one to adjust. If it doesn't move trace the vac line from the front to the source where there is supposed to be a switch that controls it. There is another adjuster down toward bottom of carb that has a tab on it( can see it in pic) that connects to the throttle positioner that also adjusts up speed. I can't remember where adjusting screw is so take a look in that region

lgene10 · 11-08-2010, 10:43 PM

new problem... i used the car last night.. when i get home and turn the engine off and start it in morning.. the engine is a hard starting now and smell gas.. i look at the sight glass the float level is fine and it is not overflowing but when i look at the carb its wet very wet...