Idle adjustment
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What would cause a car to not idle without stalling now, even though it idled without stalling before? I haven't done any serious work to the induction system. I changed out my coil and tightened and replaced some vacuum lines. The car runs fine, just will stall out when I take my foot off the gas, which it didnt do before. I am thinking that it might be that I got rid of a vacuum leak and now the mixture is too rich. Does this sound plausible as to why its not idling without stalling out?
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Comments
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If the idle speed is set pretty slow, such a change in mixture could be enough to make it die. First, double check everything you did, to be sure a vacuum hose wasn't left disconnected. If all's well, turn the idle mixture screw(s) a half turn clockwise and see if it wants to run better. If so, that would suggest your theory may be right.0
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Well, this one has me at a loss. The car just will not idle without really cranking out the idle stop screw. If I set the rpms to about 700 I try to adjust the mixture screw and there is no real change in vacuum. But when I am slowing down with the engine loaded it feels as if its stalled out.
The car will idle with the choke about 1/3-1/2 closed, at a fast 800rpms, when its warm. But as soon as I try to back off on the choke it stalls. This sounds like its the idle mixture, but backing out the screw hasnt helped. Does anyone have any ideas?0 -
Matt, sounds like some dirt or something in the idle circuit.
Bob0 -
BJ__TN wrote:Matt, sounds like some dirt or something in the idle circuit.
Bob
I thought about that, I hate to think there is dirt in the carb, since I have 2 fuel filters on the car.0 -
Something quick that often fixes a clogged idle circuit is this:
First, unscrew and remove the idle adjustment screw.
Second, take a can of spray carburetor cleaner, and using the small red pipe that fits on its spray nozzle, spray directly into the idle circuit. Put the pipe right in the idle screw hole.
As you do that, operate the gas pedal linkage through its travel several times.
CAUTION: Wear Safety glasses! you will get some sprayback. Wrapping a rag around the idle spray hole as you spray is a good idea.
Also, this is done with the engine off and cold.
I have successfully used this many times to clear an idle circuit.0 -
Have you tried changing back to the old coil? or was the old coil completely gone. If not try hooking it up temporarily to see if you idle improves. May be a bad coil.0
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51hornetA wrote:
My reasoning was that the coil works fine at high engine speeds, which is a tougher sparking condition than at idle. Why would the coil cause problems at idle, but no problems anywhere else?Have you tried changing back to the old coil? or was the old coil completely gone. If not try hooking it up temporarily to see if you idle improves. May be a bad coil.0 -
I seen some weird symptoms cause by the coil and condesor in ignitions. Strange idling and stumbling looks like fuel starving but finally is traced to ignition. Looking at your orginal post you said you changed the coil and tightened some lines. I think a quick test would be to quickly plug into the old coil and see if the problem goes away. Depends on the winding of the coil how it performs could be fine at high speed and crap at idle.
Just a thought as its a quick test to see if it helps. And while your at it I would replace your condensor as well.0 -
I agree with Sean, I had a problem that I thought was the carb. Messed with it for months. Finally I put a new condensor on and the car has never run and idled better.0
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old time mechanic told me a long time ago...." 90% of carburetor problems are in the ignition...""in other words these old carbs are pretty reliable compared to the old point/condenser/coil ignition systems. good luck. regards, tom0
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Sounds like a vacuum leak to me, if closing the choke helps then that means it needs a richer mixture, needs a richer mixture because it is drawing in extra air from the vacuum leak--Have you checked the carb to make sure it is down tight?0
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What model car and carb are we talking about?0
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Its a 38 Terraplane with the W1 397-S carb with manual choke.
The carb is tight to the manifold. Going to try to plug the vacuum port to make sure there is no leaks there.0 -
I'd clean out the idle jet first. In spite of inline filters, the micorscopic dust particles can get through and eventually block things up.
Geoff.0 -
Pulled the idle screw out and shot carb cleaner down it. It did not help the situation.0
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YOu will have to remove the actual Idle jet,. and clean it out. The idle screw only regulates the amount of fuel that goes through. If the jet is blocked, it will have no effect.
Geoff.0 -
But if I shot carb cleaner into the idle screw hole, would it not clean out the idle jet?0
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Not necessarily, as the idle screw points downwards into the venturi and will most likely only blow through the discharge hole. you will probably hae to remove the idle jet itself and blow it out with compressed air.
Geoff0 -
Can the idle jet be removed without disassembling the carb?0
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No. I can email you the relevant pages from the workshop manual if you want, but it is not that difficult to strip down. contact me if you like on geoffclark@xtra.co.nz
Geoff.0 -
If you could send that I would appreciate it.0
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