well we rebuilt the carb on my brothers s3 a few days ago because it was acting like it was running out of gas and somtimes stalling. the same day we put everything on after the fresh rebuild carb the car ran great no problems. but now the sputtering is now back, i set the floats to stock specs and triple checked everything. i already read the FAQS.

it stutters and does not want to accelerate anymore when there is heavy load on the engine, cruising up hills or in 5th most of the time. does it in 3rd and 4th and rarely in 1st or 2nd.

has new exhuast with no cat, fuel pump seems good. engine seems in good condition, pulls strong and does not smoke under heavy loads.

im lost and sorry for the long post but does anyone have any suggestions?

 

when you say it does it in 3rd and 4th, is that from a dead stop, shifting from 1st to 2nd to 3rd to 4th? or are you having gas no matter what in first and second, then third bottoms out?

 

Could be the shutter valve. Try plugging up the closet hole to the driver seat in the stock carb box on top of the carb. That would be going to the shutter valve. If bad, the shutter valve will do mostly what you are explaining.

 

this is when cruising above 40mph and getting into the higher gears. pretty much when there is a heavier load on the engine. but since first and second are pretty low its doesnt really do it in those gears.



let me check the shutter valve also.

 

Have you replaced the fuel filter lately?

 

the shutter valve is the bigger line near the driver side by the firewall correct? i plugged it up and it still acts the same. any more suggestions?

 

How's the fuel level in the float bowl sites? fuel lines crossed; ( inlet and return ?) Check your timing and spark? Just a few suggestions. Good luck.

 

Ya, that would be the shutter vlave hose you plugged. Its something else than.

 

I would suggest getting a new fuel filter also if you can.

 

fuel filter has already been replaced with a new one. could a faulty ignitor cause this? i remember on the old civic the ignitor was going out and it would die sometimes but it was random and i had to wait like 5 minutes for it to work again.

i have not checked the levels through the site glass since the rebuild, should do that tomorrow. also it idles kinda rough sometimes and it died just a bit ago when my brother pressed the accelerator.

the fuel inlet is by the firewall and the return is towered the front of the car right?

 

Check for spark, and for vacuum leaks. Are you sure you didn't put the carb spacer on upside down? Or maybe a gasket? Happens sometimes, and causes these sort of issues...

 

i dont think so, i made sure everything lined up correctly because im paranoid like that.

so the leading a trailing coils are always firing correct even at idle?

 

im going to try to adjust the mixture screw.

one thing i noticed is that the idle adjustment screw does not adjust the idle at all. i can turn it all the way to right and left and has no effect on idle. i sure its not a vacuum leak because its idleing around 200-800 most of the time.

 

Both coils should be firing at idle. Start the car and spray some carb cleaner around the base of the carb and intake. See if your idle changes.

 

already tried it, idle didnt change at all. i noticed that a bit of starting fluid while it was running made it run smooth as hell for a little bit. so i know its fuel related somehow.

 

So did you notice the fuel level in the glass sites? How are the plugs? Cap& rotor? That's about all I can think of for now. Check compression of the engine yet? starting fluid made the car run smoother. Was the car sitting for awhile?

 

it turns out the little filters on the banjo bolts for the fuel return and feed line were dirty as hell. i cleaned them up real good and reset the idle and adjusted the mixture screw and now the car runs pretty damn good. it still kinda hunts at idle but it doesnt stall or stumble anymore that i noticed. more highspeed driving will determine that.

i gave it a full tune up. if keeps up like this then all i need to fix is a crappy idle. also i the idle scew doesnt seem to work at all. i can turn all the way both ways and it doesnt raise the idle nor lower it.

 

That's not the idle screw that you are turning... Stop playing with the idle mixture screw and try to find the idle speed screw instead.

 

I had the exact same prob you are haveing, and i meen exactly the same.


I fixed the prob by replaceing the CRACKED Vac line that runs from brake booster to the manifold. Yup, can of carb cleaner found a bunch of other Vac leaks aswell.

 

isnt the idle mixture screw on the driver side right smack in the middle? and idle screw on the front towards the air pump? or is there another screw i dont know about?

 

The idle adjustment screw should be by the throttle cable towards the firewall side. It's a phillips head with a spring on it. YOu can get to it from the driver's side. It's been awhile since I worked on a Nikki carb. Get the carb manual from Trochoid and look into that. Pretty sure the idle adjustment screw is NOT by the air pump.

 

Well after reading the Haynes Mazda FSM looks like the idle speed adjustment screw is the BIG SCREW on top of the idle mixture screw (capped) . I have a Nikki carb at the shop. I'll check tomorrow for you.

checked the carb manual and on page 81 of 133 there is a part on the the carb Part # 108 called TAS (throttle adjust screw) with the spring on it. Check out the carb manual when you get a chance. I'm relearning about the rotary engine myself as well.

 

The idle screw contacts the arm that is on the end of the bell crank that the throttle cable hooks too. It will be the rear most screw on the carb.

The idle mix screw is just that, it changes the afr's of the idle, and only at idle. Once the throttle plates/butteflys move past the idle screw port in the carb throat, the internals of the carb, the jets/ports/emulsion tubes/air correctors, etc., take over.

 

What year car is this? If it is a later model then you may have to look in the appendix of the manual to get the correct information on the carb and other items that changed over the years. Rather than rewrite the manual every year, they just stick the updates in the back of the book....

 

This Nikki I have here at the shop has a little phillips screw with a 8mm jam nut for the throttle adjustment.