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Location:
Melbourne
Registered:
August 2002
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 Speed Limitation?
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Thu, 07 November 2002 16:11
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My AE82 ,4AC engine has only done 107000km. When I'm on the highway my car won't budge past the 100Km mark. My accelerator pedel is nearly fully depressed. When I press it fully (to the floor) nothing happens the car remain at 100km. I have tightened the accelerator cable to the max, timing is correct, new spark plugs & leads I'm thinking it may be the carbie since there is a flat spot when accelerating from rest or speeding up.
Any suggestions???
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Location:
Southern Sydney
Registered:
August 2002
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Re: Speed Limitation?
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Thu, 07 November 2002 21:05
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What revs and what gear is it in?
Is it a manual transmission?
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Location:
Melbourne
Registered:
August 2002
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Location:
The Central Coast
Registered:
October 2002
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Re: Speed Limitation?
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Fri, 08 November 2002 03:33
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You sure the timing is correct?
I did the timing wrong on my g/f car (it seemed as though it was heaps advanced when I checked it and backed it off) Then it ran like bog with no power! (ie: can't go very fast)
What you have to do is unplug the vacuum line to the distributor (there is a diaphram on the distributor) and plug the line to stop the vacuum leak, then adjust the timing appropriately.
If it still seems to run the same after that....check the timing with the vacuum pipe connected to the dizzy, then unplug it, seal the vacuum leak and check the timing again, from memory it should go from +20deg to +8deg (or something like that) at idle.
4AC's are usually pretty powerful and I can get mine up to 160km/h before the motor cant push the car through the wind anymore. If the diaphram on the dizzy is stuffed and torn, the motor wont advance the timing when you put your foot down.
Does that help?
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Location:
Melbourne
Registered:
August 2002
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Re: Speed Limitation?
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Fri, 08 November 2002 05:26
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My car is the same situation as you g/f. I've always timed the car with the the vacume hoses attatched to the dizzy. When i time it correctly the car pings, when I back the dizzy down a bit the car run like bog with no power. I'll do a proper timing now, but I'm more than certain that the advance unit on the dizzy is stuffed. This advance unit might also be the cause of hard starting when the engine is hot.
Actually the advance unit may not be stuffed it could be that it's not getting enough vacume. I've just checked all the hoses an none of them are leaking. Where abouts is the vacume supplied comming from? Could it be a diaphram some where under the carbie thats sprung a leak???
This may also be the problem thats causing a flat spot!
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Location:
The Central Coast
Registered:
October 2002
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Re: Speed Limitation?
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Fri, 08 November 2002 06:03
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That's exactly right! When the car was tuned properly it friggin pinged! When I backed it off, it ran like bog!
Damn it's tempremental.
I did actually have the carby repaired, the throttle valve pivot wore away and I had a vacuum leak through the throttle shaft. It idled heaps better after that and improved fuel economy and power.
You can test this by spraying WD40 (or similar) towards all the throttle linkages on the side of the carby, if the engine changes is sound when you drench it (like the revs rise or get smoother, noticably) then you have a leak there.
The vacuum line to the distibutor is actually under constant vacuum, hence why the timing is so far advanced at idle, when you unplug it, it should hiss like a snake. If it's only a gasp, you have a blockage.
The rpms should run pretty rough when you unplug it due to the vacuum leak, when you plug your finger over it, it should get a bit smoother.
I think the vacuum is supplied from two places, one, from the manifold vacuum, and two, from a diaphram on the carby to increase the vacuum advance under full throttle depression. From memory (very vague) I think it may even have two vacuum lines going onto the distributor.....but I'm not sure.
My car has instructions underneath the bonnet to tell you how to adjust the timing...it even tells you what vacuum hose to disconnect.
Nice car, pity it's got hail dents....
Not sure about flat spots though...every car I've had I've never had to deal with one....sorry 
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Location:
Melbourne
Registered:
August 2002
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Re: Speed Limitation?
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Fri, 08 November 2002 09:55
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Thanks for all your help.
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Location:
Adelaide
Registered:
July 2002
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Re: Speed Limitation?
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Fri, 08 November 2002 14:25
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i have a 1986 model 4ac and i can get it to go off the clock ie over 180km/h 
yeh im pretty sure there is two vacuum lines to the dizzy
as for the flat spot is it around 3000 rpm?? if it is thats pretty much just a prob with all 4ac's, it can tuned so its not so noticeable ie. lots of advance and run premium 
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Location:
Melbourne
Registered:
August 2002
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Re: Speed Limitation?
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Fri, 08 November 2002 14:50
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Yes the flat spot occurs around the 3000rpm. I guess its from the advance unit of the dizzy. Most people (Even a carbie specialist) have advised me to use premium unleaded rather than normal unleaded. Is it Ok for the engine to run on premium unleaded?? I was also told that premium unleaded stops the pinging noise is this true??
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Location:
Southern Sydney
Registered:
August 2002
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Re: Speed Limitation?
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Sat, 09 November 2002 00:04
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Its a 4spd auto and at 100km its about 2100 rpm
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Are you serious..... that must be one pig off the line!
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Location:
Melbourne
Registered:
August 2002
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