Quote:
Originally Posted by Mikes66
It is for part throttle driving, and low speed cruising. When driving at a constant RPM, and speed ( near 15 - 25 MPH), some folks will get a constant lean stumble, where mis-fires and bumbling along is always present.
This happens when your not quite at idle, and not quite usinig the main Booster Circuits. It is when your engine is running solely on the transistion slot circuits. The transition slot circuit also runs off of the IFR circuit. When this condition occurs, it is a great fix to increase the diameter of the IFR but 2 - 3 sizes (example .030 IFR to .033 IFR) to cure this part throttle lean.
But this does effect the idle circuit as well, and that means you need to re-turn your idling for less idle mixture.
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i've had to deal with an engine like that.
you could watch it on the AFR gauge we use. very slighty throttle opening and the gauge would climb to to 16.5:1 and POP and the engine would stall.
2 thou on the IFR and the problem was solved. though it did mean taking half a turn from each idle mixture screw. (two corner idle, 1850)
though this was a last resort. as we'd had similar problems with the same modle of car caused by the ignition system so we went down that path first
