Thread: mixture control
View Single Post
356-930 356-930 is offline
Acceleration Junkie
Join Date: Aug 2007
Location: Laguna Beach, CA
Posts: 263
Originally Posted by hipdoc View Post
. . .After I start the car, it will RPM high during warm up but then ossilate between 200-1000 RPMs for about 6 times before idling at 900. It idles fine and runs good but I was told that it's lean and that's why it ossilates.
What you describe is an initial rich condition, not lean. Too rich, which is what's needed when cold, produces the hunting/oscillation at idle. Until the WUR is truly warm, it will hold control pressure low which creates a rich fuel mixture. (AFR = Air Fuel Ratio).
Until you instrument (shove an O2 sensor up the exhaust pipe and read it) you can't adjust AFR's closely. And, if vehicle is equipped with a catalytic converter, this may throw off reading of AFR's, I don't know about the new world.
You can adjust AFR at idle to get it close without instrumentation.
Get the engine idling with air cleaner off/sensor plate exposed. Press down on an edge of the sensor plate just enough to Barely move it. If engine speed picks up, too rich. If it stumbles/slows, OK to lean. If no change, you're spot on or close to it.
Best get an AFR system, Innovate or Zeitronix or? Zeitronix about $700 with all the sensors. I installed the Zeitronix and related sensors on my 930 engine because it logs AFR, RPM, Boost, EGT and throttle position simultaneously. A seat of the pants - street dyno (if you know where you can safelly accelerate through at least 3rd gear without getting a cop's attention).
Old 11-17-2008, 02:22 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #18 (permalink)