While driving along, I noticed a sudden increase in engine rpm's between shifts: that is, when I depressed the clutch and let off on the gas, the engine actually sped up before falling slowly off.
At the next light, I noticed the idle rpm to be at about 2000, and won't come down.
At home, I noticed that the exhaust was sooty black, the engine runs rough and stays at about 2000 rpm.
No ignition problems, no apparent vacuum leaks, and the carb linkage is not stuck. I'm guessing that somehow the carb decided to run super rich for some reason.
Any ideas?
Thanks, Lynn Blasch
Carb runs rich?
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Marc
- Moderator
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Carb runs rich?
In general, it takes more air to have a higher engine speed - too much fuel without enough air for it will just cause rich running and plug fouling...if your idle was set `way lean to begin with, then extra fuel could make it gain RPM without any extra air. Is your electric choke getting warm as it should? Is the venturi softplug still in the carb body?
If you don't find a carb/vacuum leak kind of problem, make sure the distributor advance mechanism isn't stuck (it wouldn't explain the sooty t'pipes, but it could cause a high idle).
If you don't find a carb/vacuum leak kind of problem, make sure the distributor advance mechanism isn't stuck (it wouldn't explain the sooty t'pipes, but it could cause a high idle).
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Insaino Dwayno
- Posts: 144
- Joined: Fri Oct 25, 2002 1:01 am
Carb runs rich?
Check what Marc said. I also thought of
-throttle return spring, it it's unhooked, it could cause the cable to bind, and then it would just rev high.
-accelerator pump not working right or stuck maybe?
-Dwayne
-throttle return spring, it it's unhooked, it could cause the cable to bind, and then it would just rev high.
-accelerator pump not working right or stuck maybe?
-Dwayne
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clblasch
- Posts: 2
- Joined: Mon Dec 16, 2002 12:01 am
Carb runs rich?
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Marc:
<B>In general, it takes more air to have a higher engine speed - too much fuel without enough air for it will just cause rich running and plug fouling...if your idle was set `way lean to begin with, then extra fuel could make it gain RPM without any extra air. Is your electric choke getting warm as it should? Is the venturi softplug still in the carb body?
If you don't find a carb/vacuum leak kind of problem, make sure the distributor advance mechanism isn't stuck (it wouldn't explain the sooty t'pipes, but it could cause a high idle).</B><HR></BLOCKQUOTE>
Marc- Choke is O.K., I checked the float bowl and it seems normal. I got the rpm's down by backing the adjustment screw way out, but the engine still runs rough with sooty exhaust. As I rev up the engine, it goes "fl-fl-flop" out the exhaust pipe as the engine slows, which I think also points to a rich condition. The puzzle is that this problem occured instantly, and not over a period of time. Something has failed, but what?
Thanks for your rapid response.
<B>In general, it takes more air to have a higher engine speed - too much fuel without enough air for it will just cause rich running and plug fouling...if your idle was set `way lean to begin with, then extra fuel could make it gain RPM without any extra air. Is your electric choke getting warm as it should? Is the venturi softplug still in the carb body?
If you don't find a carb/vacuum leak kind of problem, make sure the distributor advance mechanism isn't stuck (it wouldn't explain the sooty t'pipes, but it could cause a high idle).</B><HR></BLOCKQUOTE>
Marc- Choke is O.K., I checked the float bowl and it seems normal. I got the rpm's down by backing the adjustment screw way out, but the engine still runs rough with sooty exhaust. As I rev up the engine, it goes "fl-fl-flop" out the exhaust pipe as the engine slows, which I think also points to a rich condition. The puzzle is that this problem occured instantly, and not over a period of time. Something has failed, but what?
Thanks for your rapid response.
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Bob Ingman
- Posts: 2869
- Joined: Mon Mar 19, 2001 12:01 am
Carb runs rich?
Lynn when you first posted this question this morning on topica I was going to ask if a loss of power was noticable as well. Since the idle has returned to normal by carb adjustment I am guessing that this is carb related and nothing very serious.
This is difficult to diagnose because there are seemingly conflicting symptoms. Fast idle is usually a result of a lean condition while black smoke is indicative of insufficient combustion( a rich condition).Jake suggested checking float condition. When doing that did you also check the float bowl inlet valve? It sometimes will stick allowing float chamber run over to occur.Keep us posted. Marc is very good at finding the sourses of these kinds of problems. Good luck. Bob Ingman
This is difficult to diagnose because there are seemingly conflicting symptoms. Fast idle is usually a result of a lean condition while black smoke is indicative of insufficient combustion( a rich condition).Jake suggested checking float condition. When doing that did you also check the float bowl inlet valve? It sometimes will stick allowing float chamber run over to occur.Keep us posted. Marc is very good at finding the sourses of these kinds of problems. Good luck. Bob Ingman