Mke:

Check the voltage at your oxygen sensor.  With the wire disconnected, engine running, I think it was supposed to put out  .3-.5 volts aprox and when I checked mine it was reading .05 volts.  It was sending a message to the brain, begging it to enrichen  the mixture.  The brain was complying, my air/fuel ratio was 9-10 instead of 14.7, my gas milleage was down to 9 miles per gallon.  After replacing the oxygen sensor my gas milleage returned to it's usual miserable 14-15 miles per gallon.  It was an easy fix.

John
  nal Message ----- 
  From: Mike Vanderzanden 
  To: vanagon@GERRY.VANAGON.COM 
  Sent: Tuesday, May 08, 2001 7:58 PM
  Subject: Running rich

  My '84 GL is running very rich.  Mileage is 10 mpg at best.  Blows thick 
  black smoke when loaded (i.e. under acceleration).  Down on power in general. 
   Idle speed is eratic but does not stall (yet?).  Been driving her daily 
  under these conditions for months. 
  Things I've done: 
  Checked/adjusted ignition timing.  Was retarded.  Now correct (at least 
  close).  Made no difference. 
  Measured fuel pressure:  36 psi at idle with vacuum connected.  42 psi (at 
  any engine speed) with vacuum line disconnected.  If increase engine speed 
  (with vac. connected), fuel pressure decreases (yes, DECREASES) to about 32 
  psi. 
  Swapped out the air flow meter for another (used but serviceable) one.  No 
  significant change in behavior. 
  Examined the spark plugs.  All four were equally black and sooty. 
  I also cleaned (with electrical contact cleaner and, in case of ground 
  connections, emery cloth) and exercised all of the connections I could find 
  on the engine management wiring harness. 
  I plan to measure the Temp. II sensor resistance tomorrow. 
  An observation:  I noticed that the position of the AFM wiper is about 20 or 
  25% "open" with the engine idling.  This seemed surprisingly high to me, but 
  I have no reference.  Could be normal.  Anyone have any input?  I also 
  adjusted the CO adjustment screw (under the plug on the AFM housing) and this 
  had no real effect on the position of the AFM wiper.  Had a small effect on 
  the quality of the idle. 

  I did a mechanical rebuild on this engine two years ago (did not do anything 
  to the fuel injection/engine management system).  It ran fine and gave me 19+ 
  mpg overall fuel mileage until this problem cropped up a couple months ago. 

  Thanks for any suggestions. 

  Mike 

  I know that there's probably been several discussions in past on this 
  subject, but I am new to this list and I haven't figured out how to search 
  the archives by subject.  Maybe someone can help this non-savy computer user 
  in this respect. 

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