[Laner-17]

Hey guys i know this is a common problem but im looking for some options with my '94 suzuki sierra.
When accelerating in any gear it lags for 2-5 seconds before opening up, ive put a new carby kit thru her and just changed the oil and filter and also the fuel filter...no change. She idles fine but when taking off it just hesistates And then kicks in all of a sudden. People i have spoken to have said that it could be an air/fuel mixture problem but on the stock carb its a fixed needle im pretty sure.

Just looking for any ideas from the pros on here that can share some insight into things i may have overlooked/missed.

Cheers

[Santos]

double partial post

[Santos]

check the throttle cable is adjusted properly and working smoothly. You want someone to push the pedal while you visually confirm that primary throttle is opening full and closing

Check that the butterfly isn't holding open when cable is connected.

Potentially the cable can catch completely and go unnoticed, the two 12mm M8 nuts that hold the cable to the carburetor should be nearer to the bend at the back. If it its closer to the middle or the tip of the tube and your throttle is closed it will likely indicate that the cable itself needs replacing. Basically what happens is the primary throttle can only partially open, engine loads up builds momentum and vacuum causes the secondaries to kick in prematurely to compensate.
At least thats best how i can visualise it.

Secondly confirm you have no vacuum leaks (good idea is replace all tubing ) and that the vacuum actuator is working, you can push it shut and seal the vacuum with your finger and it should hold the secondaries open. Do you have an adustable idle screw? Most 90's OEM ones have tamper proof covers. You can cut a slot in an existing one, replace it with a new one fund in indian maruti gypsy 1.3l carb kits or soure one from countless aisin/mikuni/nikki japanese carburetors from the 70's and early 80's.

Lastly (or rather firstly if you have one) Get hold of a Vacuum gauge and check the readings and see how the engine is behaving when you blip the throttle. You want to tune the idle so that you are get a strong steady 21 Vac reading and 10 BTC with the timing light @ 800rpm when the engine is warm from 10 minutes commute. This ensures every is up to temperature not just your coolant. Mounting the carb in reverse with everything but throttle cable hooked up is easiest way of adjusting idle screw. One you got the right numbers flip it the right way round, adjust throttle cable and you shuould see no more than 50 or so RPM change.

Many people have stripped down carbs, removing auto-choke and other stuff to simplify the carb, even with this configuration a warm engine in good condition with no vacuum leaks will sit on 800 easy (mine actually reads 700-750 strong idle most days) If you getting 1000rpm idle , 21 vac & 10 advance your 'settings'are wrong and it impacts the rest of the rev range.

[bumstein]

Good write up Santos!!

In addition id be checking for adequate spark on all cylinders. Santos mentioned the ign timing, yep very important.

Check there's no crap in the carby jets!! This will cause a lag or flat spots very easily, even if they've just been cleaned pull them out and have a look. Might just be some gunk pulled through and lodged there.

My feeling on this is you've put the carby kit through yourself. Now I'm no carby technician and this is the reason I don't overhaul my own carbys unless I'm prepared for a substandard result.

Carbys are a black art IMO, simple clean out is fine and learning how to tune the properly is grand!! Replacing parts like the Vac Advance when there is a problem is great.

Otherwise if your sure it's the carby, then find an old guy who's worked on carbys since he was 15 and now does a few in his back yard just to keep occupied, or a legit carby place to do it. Putting a carby kit through and lathering all the bits with carby clean does not always fix problems, unless your well versed in carbys then IMO rebuilding them yourself will likely yield very varying and usually substandard results.

[HarryHoudini]

bumstein wrote:

Good write up Santos!!
Otherwise if your sure it's the carby, then find an old guy who's worked on carbys since he was 15 and now does a few in his back yard just to keep occupied, or a legit carby place to do it. Putting a carby kit through and lathering all the bits with carby clean does not always fix problems, unless your well versed in carbys then IMO rebuilding them yourself will likely yield very varying and usually substandard results.

Yep,Emission era Carbies are a nightmare when they go off-song.I posted elsewhere on this Forum about my Brothers 1980's Celica,two rebuilds from specialist Co.s that were useless,same problem,no power under load and heavy fuel consumption.We finally fixed it with a Carby of a genuine wreck.

[bumstein]

HarryHoudini wrote:

We finally fixed it with a Carby of a genuine wreck.

Oh yeah!! Meant to mention this.. Rebuilds can be costly, a good second hand carby can be cheap and work well!!


Just make sure you buy a second handy from
Someone you know and/or trust, especially if it's not on the vehicle when you try it. It will still need to be tuned to your car.

[Santos]

bumstein wrote:

Good write up Santos!!

Carbys are a black art IMO, simple clean out is fine and learning how to tune the properly is grand!! Replacing parts like the Vac Advance when there is a problem is great.
.

Definitely an art to it but more in the sense you need to be meticulous in your approach. Laziness and constant jury-rigging will only cause grief in the long run. The emission band-aids that got mounted on over the years doesn't really help the situation either. By now most vehicles are 20-30 years old and the maintenance has been long neglected. All that junk is potentially making the carb drastically under perform and as a result causing more emissions than a pre-pollution configuration simply tuned.

Carburetors are about good strong vacuum signals, not any vacuum but an unobstructed clean vacuum with minimum restrictions in the 'circuits'
When i started 'fettle-ing' on mine so many years ago idling at 1000rpm was 'near enough' and 'thats what i can expect'. However It really is worth the extra effort to get the 'hot' idle screw, the 'actual/real' idle screw siting on the factory RPM at max vacuum reading on 10 degrees advance.

Then again their is school of thought that when you tinker with these things you pay more attention when running the butt-dyno is in play and you ntice the wonders of the snake oil

[Reubs]

Accelerator pump squirts fuel when the pedal is pressed?

[frak]

Basically.

I had mine wear out on my first car (old corona) years back. Nothing would happen when u put the foot down. In which case kept pumping the pedal till it would actually give me some power then hold it down. Dreaded red lights. Lots of abuse from other drivers on the road.

Idle was fine.

[evski]

Might be worth checking your fuel filter too. I've got a similar problem when warm, turns out the previous owner put the fuel filter in the engine bay and a hose where it should go. Then a dodgy electric pump going into the carby. So I reckon that will be my problem, going to drop the Tank on the weekend and run new lines then set the timing. Hopefully sorts it out.

[Laner-17]

Sorry for the late reply fellas...the suzi keeps me busy
I tried all the things that santos mentioned and still the same problem, i may pull it open again and just 100% check the jets are clear but if that doesnt work i think she may have to see a few days in a suzi specialist shop.

On a side note, any of u fellas done the vitara 1.6 or gti swap....starting to think efi is the way to go thus reducing carby algebra.