Thread: Carb rough idle
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Old 10-03-2012, 04:08 PM   #6 (permalink)
christofoo
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Join Date: Mar 2012
Location: Salt Lake City
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00C - '00 Toyota Corolla
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Quote:
Originally Posted by ron View Post
1 has rich or oil , 2 looks normal, 3,4 normal or no spark,or lean condition at idle. sounds crazy but what do they smell like,oil,fuel. as I recall it runs ok at speed ,how is your charging system & battery may not be enough power output till its up in rpm's or fuel pressure is low at idle . Lots for you to check .
I remember sniffing plug 1 once and not detecting anything in particular, maybe a little fuel... but you know when I switch the key off the it's the ignition that dies, the manifold stays wet and the cylinders will end up with a little fuel sitting in them (right?). That's why this type of engine can diesel after killing the key if the plugs are too hot (timing over-advanced), similarly sometimes if I don't pump the pedal before starting it will start right away but then stall.

At speed it usually runs okay, a while back I was having a little shudder in gear at low-to-mid throttle that I thought might be misfiring.

I do have a volt meter in the accessory port and I cleaned up the battery with a desulfating charger, so I do know the battery / charging system is in good shape.

Last night tinkering with things I noticed that once in a few hours I will hear a tiny little bubbling sound (high frequency, like a buzz) for about 30 seconds. Next time I will have my stethoscope ready and be able to pinpoint it. I'm betting that air is getting drawn into a fuel line somewhere, and the fuel is backing down the line, and fixing it will eliminate the need to pump it before starting. I doubt that air in the lines is the explanation for rough idle though; it idles rough even after a 10 mile drive. (Unless the air entry is occurring much faster when the engine is turning.)

Last edited by christofoo; 10-03-2012 at 04:17 PM..
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