Stumble On Acceleration.

[Rolliac]

Ok well the primary throttle shaft on my ASIAN 3k carb has a bit of play. Now if the engine is off and I pump the accelerator so the pump jet is squirting you can see fuel starts to seep past the throttle shaft on the outside of the carb.

 

Is this normal? I’m wandering if this could be the cause of the stumble on acceleration?

 

Whether the engine is idling or at any rpm, when I push the accelerator down the engine drops revs before increasing revs/ acceleration. In some cases the engine could stall.

 

This is seriously hindering performance and I’ve tried every thing I can think of to fix it. Carby kit, clean carb, adjusting idle mixture, timing, plugs & leads, filters, compression test, manifold & exhaust leaks ect. Even put in a new head gasket but none of this helped.

 

Anyone? I’m going insane.

 

I’m going to hunt down another throttle plate anyway just to be sure.

[Evan G]

Ok well the primary throttle shaft on my ASIAN 3k carb has a bit of play. Now if the engine is off and I pump the accelerator so the pump jet is squirting you can see fuel starts to seep past the throttle shaft on the outside of the carb.

 

Is this normal? I’m wandering if this could be the cause of the stumble on acceleration?

 

Whether the engine is idling or at any rpm, when I push the accelerator down the engine drops revs before increasing revs/ acceleration. In some cases the engine could stall.

 

This is seriously hindering performance and I’ve tried every thing I can think of to fix it. Carby kit, clean carb, adjusting idle mixture, timing, plugs & leads, filters, compression test, manifold & exhaust leaks ect. Even put in a new head gasket but none of this helped.

 

Anyone? I’m going insane.

 

I’m going to hunt down another throttle plate anyway just to be sure.

 

i think I'm having the same problem when cold starting (prob not as bad) and stumbles every worse when the choke is on?, it stalls when coming fast into a round about and turning, ill have to adjust the fuel float and get all the mixuters right and dyno it at tafe :wink:

[Jimpoole]

I can pretty much say it's gonna be the carby. :wink:

If I come down a hill, downshifting to 3500rpm each gear, and then accelerate around a corner, it'll give a jolt and take a split second to take off.

I'm thinking this means a lean idle mixture, or in your case really lean. Or really rich. I'm probably not telling you anything you don't know, but the only thing that will give you these effects is definately the carby.

Petrol on the outside of a carby is not normal.

How does it go up at say, 60kp/h in fourth? Does it jolt along? Bog down terribly on acceleration?

And are you sure you have the idle mix adjusted correctly? That sounds like your problem right there.

Before you go to take off, give the accelerator a blip and see if this is any better.

[Taz_Rx]

....or just take the opportunity to invest in a weber! :wink:

[Jimpoole]

....or just take the opportunity to invest in a weber! :wink:

Perhaps a good idea. But if he doesn't have $200-$300 to get a good one, (like me) he has to make do wih what he has.

[Falken_KE30]

....or just take the opportunity to invest in a weber! :wink:

 

and maybe some of use want to keep the fuel economy :wink:

[Rolliac]

Wow thanks for your input.

 

How does it go up at say, 60kp/h in fourth? Does it jolt along? Bog down terribly on acceleration?

 

Yes it bogs down on acceleration.

 

Tomorrow I’ll go to the wrecker and hunt another throttle plate (or whatever it’s called) maybe the hole carb.

 

Failing that I’ll just drive the car off a cliff with me still in it coz it’s driving me nuts.

 

Or invest in a 32/36 or side draft.

[Falken_KE30]

Wow thanks for your input.

 

 

 

Yes it bogs down on acceleration.

 

Tomorrow I’ll go to the wrecker and hunt another throttle plate (or whatever it’s called) maybe the hole carb.

 

Failing that I’ll just drive the car off a cliff with me still in it coz it’s driving me nuts.

 

Or invest in a 32/36 or side draft.

 

I know how you feel buddy, mines not been well for sometime, boggy on take off, boggy acceleration, by time it feels right in the revs its time to go up a gear.

 

Biteing the bullet and doing a big service,

 

Dizzy cap, points, spark plugs, Carby Kit, fuel filter, all the manifold gaskets and carby ones... if that fails then ill join ya with the cliff dive :wink:

Edited July 7, 2009 by Falken_KE30

[Jimpoole]

So is it the throttle plate that is causing the leak? If so, I think your car may not be getting enough fuel because it's leaking out of the side.

Is it difficult to start?

Second hand Aisan carbs can be had for cheap I believe.

If you can't get one, try find a Nikki off a Gemini. They are said to be highly underrated, and only need a different adaptor plate to fit. It's in the FAQ.

If that doesn't work, for your own good, call this number: SANE Australia Helpline: 1800 18 SANE :wink:

[Taz_Rx]

^^ Gemini Nikki's and also mazda Nikkis bolt onto the stock manifold with no adapter plate. :wink:

Sometimes just need to grind some of the casting for bolt holes (air cleaner etc) off the manifold to clear the throttle linkage.

[altezzaclub]

Petrol running out the throttle shaft is normal if you're pumping the throttle and the pump jet is working.

 

There's always some clearance around the plate shaft and the liquid fuel runs over the plate and along the shaft.

 

Aside from that, it does seem like a carb problem. If bogging down is worse with choke on I assume its too rich, which is usually related to float level. If bogging down is improved by running on choke then its too lean, an airleak somewhere.

 

..and bogging down in a corner is common as all the petrol runs to one side of the carb floatbowl. You can usually re-set the float level to help, but its one of the big advantages of fuel injection.

[Rolliac]

Cool

 

Yeah only seeps past throttle shaft with engine off and pressing accelerator. I guess when the engine is running it’s sucking some air past the shaft so it doesn’t happen. So could be too lean???

 

I’m going to try the choke trick.

 

Problem is the same whether cornering, straight or in neutral.

 

Hitting the wrecker today.

 

Thanks a lot guy’s. Much appreciated.

[Falken_KE30]

what you mean by throttle shaft?

 

Do you mean the accelerator pump that has a like a rubber grommet around it and it sits on top of the carb with a link to it? .... what a mouth full :wink:..

 

If so mine leaks a bit, seems a common problem when the pump starts to wear out and same for the rubber boot thing.

 

EDIT, re read your first post, silly me lol. Id say grab a new carb if its leaking past the shaft, thats not normal

Edited July 7, 2009 by Falken_KE30

[Felix]

A few things to pay attention to in stock aisan carbs that are easily overlooked.

 

The air corrector drillings. These are one piece with the auxillary venturis. The air correctors are tiny and are easily blocked with a bit of dirt. Also if the screws for the auxillary venturis are loose, you will suck air leaning the mixtures excessively.

 

Power valves. They can get sticky.

 

The screws between the upper half and lower half of the carb. These can loosen off and give a vacuum leak.

 

Accelerator pump diaphram. If it is worn you will get a reduced pump shot.

 

Personally I hate the aisan carbs, but they are much better suited to a K series than an oversized 32/36. With a little work and understanding of the different carb circuits you can make decent power gains especially when matched with other mods such as sports filter, extractors/exhaust, cam, headwork. The venturis are different sized between models and can be easily substituted for more airflow if you put larger ones in.

 

Other things you can do to improve airflow (with any carb) are polishing the internals of the venturis, removing the choke flap, and if you're really keen thinning the throttle shafts and knife edging the throttle butterflys.