Car hesitates when you stab the throttle.?

[siggywagon]

Gday, I got an 82 sigma and in neutral when you stab the throttle down a bit for a split second it dies then revs up...does anyone know why its doing this? Ive changed plugs leads air filter fuel filter. Also with the vacuum advance hose on the dizzy I can remove it and the revs dont drop...but when I put a hose straight from the from the dizzy to the inlet manifold and bypass all those t peices it raises the revs a tad, is this normal? Or should I leave it the way it was.
Another quick question, what is the little round thing near the battery with a vac line coming off it to the manifold, its got a wire connector off it too.
Thanks

[GLANT]

Gday, I got an 82 sigma and in neutral when you stab the throttle down a bit for a split second it dies then revs up...does anyone know why its doing this? Ive changed plugs leads air filter fuel filter.

Another quick question, what is the little round thing near the battery with a vac line coming off it to the manifold, its got a wire connector off it too.
Thanks

faulty accelerator pump/ or blocked accelerator jet... could be causing cough??? take air cleaner off, and actuate throttle butterfly, look in carb at same time and you should see a little squirt of fuel if all is ok....

round thing??? is economy light sensor ( uses same light on dash as low fuel light) .... its a cream color round plastic thing, with a screw in top pointy bit to adjust it.. it comes on when you accelerate to heavy....its a vac switch..

[ddt]

it could be you have an air leak bypassing the carby. Either at the base of the carb or at the manifold?

Could also be the carby itself;
The accelerator pump on the carb is meant to meter extra fuel when you suddenly accelerate. Without it, the mixture will be too lean for a moment and could cause hesitation.

Worth checking your vacuum advance diaphram too. Just connect a bit of hose directly to it with the dizzy cap off and suck as hard as you can- should see slight movement in the dizzy. You definitely shouldn't be able to suck air through it -if so it's forked.

[tonycrouch]

My sigma has this exact same prolem.

The problem can be brought on moreso if you're running additional accessories. For example, with it in neutral (and with the automatic choke worn off), the engine will happily idle @ 900rpm.

If you turn on electrical accessories one by one (ie. wipers, cabin a/c fan, aux radiator fan, spotties, blah blah) you'll notice that as you turn on each device the revs will drop (sometimes 100rpm per device). If you've got to turn quite a few on at once, you have to rest your foot gently on the accelerator to stop it chugging @ the lights while in neutral.

Does this occur in yours also?

Cheers,
TC

[siggywagon]

Cheers for all your replies.
Now, I removed the air cleaner and moved the throttle linkage with the engine off but didnt see any fuel coming out the jets?

On the subjects of carbies, my secondary butterfly is not opening at wide open throttle.. I took the short vac line from the little diaphram to the carby off and could not blow down the carby side. BUT when I connect it straight to manifold vacuum through a t peice, it works fine and both butterflies open up. Would there be a blockage in the carby where the vac line goes causing it not to suck through? Could I keep it running like this?

Ahh lol yeah I found out about that little fuel light thingy near the battery, just disconnected it.

I checked my vacuum advance diaphram and it seems all good, I could not suck through it but could hear it moving. Is it cool to run the vac line from vac advance to the little pipe off the bottom of the manifold? It was where all the others went but I took most of them off or blocked them so now just have 1 (or 2 if you count the one that goes to secondary diaphram)

When I load up all the accesories its not too bad, it probably drops about 100 rpm but I dont have that many accesories.

The biggest problem I am having is pinging!! I have the dizzy now retarded all the way otherwise it pings really bad. I would really appreciate if someone could come up with a few suggestions as to why.. Its got new plugs, new leads, air filter, fuel filter, a couple of 98ron tanks of fuel run through it - now running 95ron. The car had been sitting a while maybe 6 months before I got it and I did an oil change to thicker stuff coz it blew a bit of smoke. Apart from that it runs good but its doing my head in! I also put 2 cans of upper engine cleaner to clean all the carbon off the cylinders but didn't really do much. Checked for vac leaks but didn't have many hoses to check. I did muck around with the mixtures in the carby a little tho coz am getting bad fuel economy...
Any suggestions?

Thanks again!

[davetrees]

If you turn on electrical accessories one by one (ie. wipers, cabin a/c fan, aux radiator fan, spotties, blah blah) you'll notice that as you turn on each device the revs will drop (sometimes 100rpm per device). If you've got to turn quite a few on at once, you have to rest your foot gently on the accelerator to stop it chugging @ the lights while in neutral.

When you draw more power, the alternator works harder ... therefore putting more load on the motor via the belt. That's normal.

With all those "electrical extras", are you still running the stock alternator ? An upgrade might be in order .....

[rogervize]

I also have this hesitation problem with my '78 Scorpion.
Tried sucking on the vacuum advance and it doesnt respond at all. It seems to be letting in air.
Ive never had a faulty vacuum advance before ..is this likely to be the prob?
Also there doesnt appear to be much vacuum from the manifold.
Thanks for any advise.

[rogervize]

Can someone please clarify the correct routing of fuel lines on my '78 scorpion. ie...the lines supply the accelerator pump and recirculate back to the tank.
Thanks.

[rogervize]

Car='78 Scorpion 2L Astron
Prob= Tried the vacuum advance test by sucking on the hose.it lets in air but I cant hear from where.
What next? Disassemble the mechanism and repair diaphram? How does the distributor wear on these cars.perhaps I need a new distributor?
Also I did not see any fuel pump jet when observing through the inlet..I guess I will have the carby refurbished.
I initially thought my probs were due to carby being clogged but it could also be lack of advance combined with failure of the accelerator pump.
I was suspicious of the engine miss and checked the spark on my analyzer. Any thoughts?
Appreciated...Roger

[tonycrouch]

If you turn on electrical accessories one by one (ie. wipers, cabin a/c fan, aux radiator fan, spotties, blah blah) you'll notice that as you turn on each device the revs will drop (sometimes 100rpm per device). If you've got to turn quite a few on at once, you have to rest your foot gently on the accelerator to stop it chugging @ the lights while in neutral.

When you draw more power, the alternator works harder ... therefore putting more load on the motor via the belt. That's normal.

With all those "electrical extras", are you still running the stock alternator ? An upgrade might be in order .....

Yeh mate, had to get the alternator rebuilt a couple of months back when it went belly-up. However, it's still the stock version. Perhaps I should've spent the extra $ and got an upgraded one while I was there ... oh well.

I hoping if I wind in the hot idle screw a fraction it might help the hesitation a little.

[81GL]

My sigma has this exact same prolem.

The problem can be brought on moreso if you're running additional accessories. For example, with it in neutral (and with the automatic choke worn off), the engine will happily idle @ 900rpm.

If you turn on electrical accessories one by one (ie. wipers, cabin a/c fan, aux radiator fan, spotties, blah blah) you'll notice that as you turn on each device the revs will drop (sometimes 100rpm per device). If you've got to turn quite a few on at once, you have to rest your foot gently on the accelerator to stop it chugging @ the lights while in neutral.

Does this occur in yours also?

Cheers,
TC

Sounds to me more like your vacuum advance is not working correctly. More loading at idle should be advancing ignition to compensate.

Car='78 Scorpion 2L Astron
Prob= Tried the vacuum advance test by sucking on the hose.it lets in air but I cant hear from where.
What next? Disassemble the mechanism and repair diaphram? How does the distributor wear on these cars.perhaps I need a new distributor?
Also I did not see any fuel pump jet when observing through the inlet..I guess I will have the carby refurbished.
I initially thought my probs were due to carby being clogged but it could also be lack of advance combined with failure of the accelerator pump.
I was suspicious of the engine miss and checked the spark on my analyzer. Any thoughts?
Appreciated...Roger

Unlikely for the dizzy to be worn out, even if it were, that only means a sloppy shaft, not effecting advance directly. Assuming hoses are not perished, then the diaphragm will be foobared, shouldn't be able to suck any air past it when operating correctly.
When looking from the top of your carby into the primary throat, it's pretty obvious when the accelerator pump is working, so if your not seeing any fuel shooting in then there is something amiss with the pump jet setup. Get a work shop manual and take the top of the carby apart and investigate.

[siggywagon]

Cheers for all your replies.
Now, I removed the air cleaner and moved the throttle linkage with the engine off but didnt see any fuel coming out the jets?

On the subjects of carbies, my secondary butterfly is not opening at wide open throttle.. I took the short vac line from the little diaphram to the carby off and could not blow down the carby side. BUT when I connect it straight to manifold vacuum through a t peice, it works fine and both butterflies open up. Would there be a blockage in the carby where the vac line goes causing it not to suck through? Could I keep it running like this?

Ahh lol yeah I found out about that little fuel light thingy near the battery, just disconnected it.

I checked my vacuum advance diaphram and it seems all good, I could not suck through it but could hear it moving. Is it cool to run the vac line from vac advance to the little pipe off the bottom of the manifold? It was where all the others went but I took most of them off or blocked them so now just have 1 (or 2 if you count the one that goes to secondary diaphram)

When I load up all the accesories its not too bad, it probably drops about 100 rpm but I dont have that many accesories.

The biggest problem I am having is pinging!! I have the dizzy now retarded all the way otherwise it pings really bad. I would really appreciate if someone could come up with a few suggestions as to why.. Its got new plugs, new leads, air filter, fuel filter, a couple of 98ron tanks of fuel run through it - now running 95ron. The car had been sitting a while maybe 6 months before I got it and I did an oil change to thicker stuff coz it blew a bit of smoke. Apart from that it runs good but its doing my head in! I also put 2 cans of upper engine cleaner to clean all the carbon off the cylinders but didn't really do much. Checked for vac leaks but didn't have many hoses to check. I did muck around with the mixtures in the carby a little tho coz am getting bad fuel economy...
Any suggestions?

Thanks again!

Does anyone have any ideas why my car is still pinging? Its also very gutless but thats probably coz the timing is retarded a lot and the secondary butterfly isnt opening.

What are these things like on fuel?? Its a 4spd manual with no mods. What are people getting? Ive done 180km from a full tank and its on half. Thanks

[81GL]

Can be a result from many factors, so bit hard to say "it's this" with out having the car to look at.
Bit more information might help get to the bottom of it though.
-when does it mainly do it? when cold? or at running temp?
-Low RPM mid, or high?
-Under gentle throttle or hard throttle?

Have you noticed any other "odd" things the engine does like using coolant?

As for fuel usage. How many Km's has the engine done? 180Km's around town if your playing with it a bit from half a tank would be right. Given that your complaining about detonation though & the timing is retarded a lot to compensate, it's probably fair to say now isn't really the time to compare fuel economy

EDIT: Re-reading your original post, if the vehicle is still hesitating when you try to accelerate, detonation could be hand in hand as a symptom of the accelerator pump being foobared.

[leigh7005]

i had a gemini thats use to do this on a weekly basis take yr air cleaner off and choke the carby with yr hand while you hold the revs at 3000rpm and keep the revs up do it for about 3-4 secs but try not to let it stall as it will flood itll clean out ur jets the easy way

[leigh7005]

also if u have carbon buld up on ur valves this will lead to detonation get yr engine to running temp take yr air cleaner off hold the revs at say 2000 rpm and tip some brake fluid down the carby will clean the carbon off yr valves

[gmhighflow]

[quote="siggywagon"]
I removed the air cleaner and moved the throttle linkage with the engine off but didnt see any fuel coming out the jets?


quote]

That's your hesitation problem. I have had 3 sigma carbies block the accelerator jet and i'm on my forth carby now which is good so far.Not sure if it is common for these to block up but it was for me.

As soon as I replaced the carby all was good.

[rogervize]

My sigma has this exact same prolem.

The problem can be brought on moreso if you're running additional accessories. For example, with it in neutral (and with the automatic choke worn off), the engine will happily idle @ 900rpm.

If you turn on electrical accessories one by one (ie. wipers, cabin a/c fan, aux radiator fan, spotties, blah blah) you'll notice that as you turn on each device the revs will drop (sometimes 100rpm per device). If you've got to turn quite a few on at once, you have to rest your foot gently on the accelerator to stop it chugging @ the lights while in neutral.

Does this occur in yours also?

Cheers,
TC

Sounds to me more like your vacuum advance is not working correctly. More loading at idle should be advancing ignition to compensate.

Car='78 Scorpion 2L Astron
Prob= Tried the vacuum advance test by sucking on the hose.it lets in air but I cant hear from where.
What next? Disassemble the mechanism and repair diaphram? How does the distributor wear on these cars.perhaps I need a new distributor?
Also I did not see any fuel pump jet when observing through the inlet..I guess I will have the carby refurbished.
I initially thought my probs were due to carby being clogged but it could also be lack of advance combined with failure of the accelerator pump.
I was suspicious of the engine miss and checked the spark on my analyzer. Any thoughts?
Appreciated...Roger

Unlikely for the dizzy to be worn out, even if it were, that only means a sloppy shaft, not effecting advance directly. Assuming hoses are not perished, then the diaphragm will be foobared, shouldn't be able to suck any air past it when operating correctly.
When looking from the top of your carby into the primary throat, it's pretty obvious when the accelerator pump is working, so if your not seeing any fuel shooting in then there is something amiss with the pump jet setup. Get a work shop manual and take the top of the carby apart and investigate.

Thanks for your help... I am having the carby repaired at the 'Carby Shop' ..Nigel says there is a ball and spring valve adjoining the float bowl which will be the problem with the accelerator pump.
Regarding the dizzy vacuum advance...what can be done to repair the diaphragm?

[81GL]

Thanks for your help... I am having the carby repaired at the 'Carby Shop' ..Nigel says there is a ball and spring valve adjoining the float bowl which will be the problem with the accelerator pump.
Regarding the dizzy vacuum advance...what can be done to repair the diaphragm?

Last time I checked new diaphragms are still available, there's a good chance the guy doing your carby rebuild could get his hands on them aswell. Otherwise any retailer should be able to get them once you explain what your after lol. be aware, I've seen some disturbing price differences between retails for the same branded product, so calling around wouldn't hurt.
-Very easy to replace, if you get stuck PM me & I'll upload a couple pages from a manual to help.

Nick.

[ddt]

Regarding the dizzy vacuum advance...what can be done to repair the diaphragm?

Dude, I thought it tested OK?
I couldn't find any new replacement ones for the sigma when i found mine was shot -had to get 2nd hand one. There's a 3 digit number stamped onto the connecting rod indicating the internal spring stiffness. i found there to be a couple of different ones out there for sigmas for some reason -i replaced mine with a different numbered unit but still works OK.

[rogervize]

Thanks for your help... I am having the carby repaired at the 'Carby Shop' ..Nigel says there is a ball and spring valve adjoining the float bowl which will be the problem with the accelerator pump.
Regarding the dizzy vacuum advance...what can be done to repair the diaphragm?

Last time I checked new diaphragms are still available, there's a good chance the guy doing your carby rebuild could get his hands on them aswell. Otherwise any retailer should be able to get them once you explain what your after lol. be aware, I've seen some disturbing price differences between retails for the same branded product, so calling around wouldn't hurt.
-Very easy to replace, if you get stuck PM me & I'll upload a couple pages from a manual to help.

Nick.

Thanks ..I had the carby overhauled and the hesitation is gone :-)
The vacuum advance is not working as the diaphragm is ruptured.
I will look for a replacement.
Can you tell me what other car models would use the same dizzy as my '78 Scorpion.
Presume 2.6L Sigmas would be the same? There is a L200 dizzy on Ebay(New) for $100...it looks similar.

[siggywagon]

Thanks for your replies. It does it worse when its warm, usually when you load the engine, going up hills or even high revs, pretty much all the time you put more than quarter throttle down. It does it really bad in the heat - I have backed the timing off most of the way and its quietened it down a little.

Engine has done 160,000k and not using coolant. I had to do an oil change to some thick penrite stuff for old cars coz it blew a lot of blue smoke but doesn't do it at all now or use oil. I think it was used for towing a bit. Another thing...its leaking a little bit of oil under the rear of exhaust manifold I suspect its head gasket? There is no oil in water or vise versa but its just weaping out between head and block. I have changed rocker cover gasket.

Heh yeah was just wondering what other people were getting out of there astron 2000, I am now just under 1/4 tank and have done 310km.

I used 2 cans of suburu upper engine cleaner and smoke pssed out the exhaust. I think it might be accelorator pump as 81gl said...whole carby could do with a rebuild I think as cant see fuel spraying out with engine off. Would this be why it is really gutless? Even when I hook up the secondary diaphram on the carby to manifold vacuum it just makes it ping more. There is no difference between half and full throttle.

Is it easy to get carby parts ie acc pump and carby kit coz I might rebuild it?

Cheers.