Frequent drip from main jet after lean drop complete

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Joined
Apr 29, 2010
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Arizona
Ok, can't find something close to my problem with the search...

77 FJ40, stock under the hood, runs great except...

I failed idle emissions (CO) and I'm sure it's due to fuel coming from the main jet instead of the idle circuit.

Sitting at home, vehicle well warmed up, (hood up), I did the lean drop method to adjust idle (per the FSM). It works GREAT! Zero drips from the main jet and idle is solid. O2 sensor reading is just where I want it.

Here's the problem:
On the way to DMV Emissions test, sitting at a stop light, the tach was going from over 700 back down to 650 or so. The O2 sensor that is installed also showed a rich-lean-rich-lean variation, it was sinusoidal if that helps...

Stopped in a parking lot and shined a flashlight down the carb and could see a drop from the main jet every 5-8 seconds.

I'm guessing that after shutting the hood and letting the heat build up real good, something changed.

Any ideas?

My plan today is to check all vacuum lines...

Thanks! Eric
 
If the float level is okay, the throttle plate is too far open at idle and you may need to back off the idle speed screw. If you can't get a good idle with the mixture and speed screws, look for a vacuum leak or a plugged idle circuit in the carb. . Be sure to double check your timing too.
 

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