1.3 carb stalls once revs drop from above 3000rpm *fixed*

[Tooheys]

I have an 85 sierra with a manual choke carby.

Problem is that after it is warm when stopping at traffic lights from high revs, the revs will hold at around 1500 - 2000rpm. A blip of the throttle is sometimes enough to get it back to idle or pulling on the choke.

It doesnt happen everytime i stop. I have replaced all the vacuum hoses. I have also adjusted the idle up vac solenoid for the lights/fan/rear demister. Sprayed carb cleaner into the carby.

Reading the manual I see that there is a dashpot valve for emmisions that stops the throttle from snapping closed and mine doesnt have this.
Also from the manual I can see that the PCV has been disconnected on my motor.

Timing is correct had a mate run a light over it awhile ago to get it running.

Hoping somebody has had this problem before and knows what I have missed.

Thanks,

Paul

[lay80n]

If the PCV has been disconnected, make sure that is has been blocked off. Check that your inlet manifold gasket is not leaking too.


Layto....

[Tooheys]

PCV seems to be blocked off properly and has a new gasket on the inlet manifold. Will check that all the bolts are tight later though.

Paul

[Santos]

check your manual in the emmisions section for the HIC,
hot idle compensator

you didnt mention if it was hooked up or working

[Tooheys]

Thanks santos I just double checked the HIC and there was a kink in the new vacuum hose I had just put on so I have shortened it so it doesnt kink.

From a quick lap around the block it seems better but the idle is now pulsing a little bit. See how it goes tommorow but hopefully this has fixed it.

Cheers,

Paul

[Santos]

try re-setting your idle now when its warm again, if you set it previously the kink may have thrown it out and so now you've fixed it the screw setting is off?

[Tooheys]

Well the HIC is all connected but now when the revs falls the motor will stall most times. Some of the time it will still do the high idle but most times it will just stall once the revs are allowed to fall to 1000rpm from anywhere above 3000rpm.

I have also replaced the fuel filter with no difference.

Also Investigated a carb kit and have been told that they dont have a kit
to suit a manaul choke carb because suzuki's never came with them. Find this a bit strange when the Workshop manual shows a manual choke carb. Does anyone know the part number for a carb kit for this carb??

Cheers,

Paul

[adrian`]

mines doing the same thing, whats the HIC, is that on the carby. i just put a carby kit through mine and a new fuel filter, blew out all the fuel lines. the only thing i can think of now is a fuel pump

[Santos]

other than the choke the carbs are the same, all the gaskets, float etc shnould be identical, the manual carb is not in many of the factory ser4vive manual, i have 3 and dependikng onh whnen they are printed/which market the info varies

maybe if you try getting the dashpot valve that you said you are mssing, this is supposed ease it back into idle, at a guess the throttle is snapping shut and creating a starvation of fuel while the engine still rotating at 3000rpm.

=> its how i turn off my lawn mower

[Tooheys]

HIC is the hot idle compensator works off vacuum. Not entirely sure how it works though.

Yeah I did have the same thought that it could be fuel pump.

Looking at the workshop manual santos the dashpot is not shown in the diagram on the manual choke carb. Everything in that diagram I have on my carb.

[Santos]

reaaly?
going to have go get the manual :S
the have you tested the hic? just put it in boiling water and then see if air passes through it, my understanding is when the engine run hot the more fuel is vapoursing thereby running rich so by adding a ' bypass' you can get more air in to balance it out (where as simply opening the throttle a bit more would just richen the mixture)

[adrian`]

sorry i ment what is the HIC as in whats it look like andis it attached to the carby?

[Tooheys]

Got the carby rebuilt and so far its purring like a kitten. Did a couple of laps of the block and its running like it should.

Cheers,

Paul

[david123]

If the PCV has been disconnected, make sure that is has been blocked off. Check that your inlet manifold gasket is not leaking too.


Layto....

forgive my ignorance, but I was under the impression that the 1.3l was a positive displacement sump, as in, pressurized.

Wouldn't blocking off the pcv over pressurize ??

[Santos]

If the PCV has been disconnected, make sure that is has been blocked off. Check that your inlet manifold gasket is not leaking too.


Layto....

forgive my ignorance, but I was under the impression that the 1.3l was a positive displacement sump, as in, pressurized.

Wouldn't blocking off the pcv over pressurize ??

]


there is a T piece so it would send all the pressure to the factory airbox, i think lay was saying

block the hole which would suck huge amounts of air into the intake.

[Santos]

sorry i ment what is the HIC as in whats it look like andis it attached to the carby?

missed this earlier

look at the top of the carb, you will see a vent tube on the non-choke plate side, next to it is a vacuum hose that should run to a rectangular box which then has a hose that goes to an entrace at the botom of the carb below the plates
that rectangular box is the hot idle compensator

[lay80n]

If the PCV has been disconnected, make sure that is has been blocked off. Check that your inlet manifold gasket is not leaking too.


Layto....

forgive my ignorance, but I was under the impression that the 1.3l was a positive displacement sump, as in, pressurized.

Wouldn't blocking off the pcv over pressurize ??

]


there is a T piece so it would send all the pressure to the factory airbox, i think lay was saying

block the hole which would suck huge amounts of air into the intake.

Cheers Santos

Layto....