How would one check the Oxygen sensor to see if it works ??  I replaced it about 4 months ago but for some reason my MPG went to crap - like 12 MPG !!!!!  I thought it was the Carb so I replaced it with a Pony carb from north of the border. It seems to be running OK -- Lots of black soot at the tail pipe though.  I can't seem to get a handle on it. When I first got this rig I was getting 24 to 28 MPG -- now I can watch the guage go down !!!!
Any help would be great --- Mac0

my gf's got the same problem, we got the same question lol it sucks !! its sooo bad on gas

  I'm  just thinking -- If I replaced the carb with the pony carb -- is the oxygen sensor even doing anything ??  If not -- what the crap is casing this low MPG

you don't need an O2 sensor if your running carbs. if your getting black out the exhaust it sounds like your running too rich, which would explain you low mpg.

Really !!  This is a 87' that had the stock carb and everything on it and the sensor hooked up to a blug that is in the wiring harness. ?

  What would be a good way to adjust the mixture ?? I've been playing with that just to get it to idle down.

 What would be a good way to adjust the mixture ?? I've been playing with that just to get it to idle down.

If it's made for the vehicle, you really shouldn't have to mess with jets or anything else internal.  You should have an idle air/fuel mixture screw(s) on the carb.  Did you get an instruction manual with it?

Really !!  This is a 87' that had the stock carb and everything on it and the sensor hooked up to a blug that is in the wiring harness. ?

Yeah! If you have taken the stock carburator off and put on a phony carb then you don't need the O2 sensor. Actually, you can unplug and chuck your ECM under the dash if you wanted to.

To get the milage back. I'd suggest putting the stock carb back on the car and trouble shoot the problem. I mean, you had good mileage before something broke, right? Start with checking the O2 sensor as perscribed in the FSM and then move on to the Fuel Mixture Solenoid on the carb.

The FSM has you take the O2 sensor and put it into water. With it in water, you take an resistance measurement. Off hand, I don't remember the ohm range you're looking for. I'm sure someone has that info close at hand.

I hope this helps, Eric

Here's how I learned to adjust the mixture way back when there was lead in the gasoline:

1.  Start it up and let it warm up.
2.  Check to be sure the choke has opened up!!!
2a.  If not, clean the butterfly valve linkage (on the outside) with carb cleaner.
3.  Slap your hand over the exhaust (or close to it) for a second.  Smell it.
3a.  Does it smell like gas?  If so, you're running too rich.  Turn the screw in a half turn, and go back to step 3.
4.  Now that it DOESN't smell like gas, turn the screw out a half turn.

That should do it.

Why not just go EFI  

  Well I don't think putting the old carb back on is a option - Gone already !! All I have read about these pony carbs has been good so I hope I am just missing something. That mixture screw for the idle is what I have been messing with- when I turn it all the way in the rpms go up ?? Shouldn't they go down ??
No EFI for this kid ---- it's going to be a VW diesel -- but I was hoping not till this fall.

Thanks for the help here guy's --

That mixture screw for the idle is what I have been messing with- when I turn it all the way in the rpms go up ?? Shouldn't they go down ??

No.  It's running more efficiently, so the rpms WILL go up.  When it's too rich, you're choking it with unburned fuel.  So adjust the mixture, THEN turn the idle speed back down, by adjusting the THROTTLE, not the MIXTURE!

Well mine situation is a little different I HAVE an EFI and I get 15 MPG   FIX IT GUYS

  The edle screw on the linkage is all the way out -- not doing a thing .. ??

 The edle screw on the linkage is all the way out -- not doing a thing .. ??

Well, that's a drag.  Really though - properly adjusted, the mixture will give you the MAXIMUM RPM at any throottle setting.  While it's running, turn it in slowly, and listen to the RPMS increasing.  When they start dropping again, you'll be running lean - open it back up a quarter to a half turn.  Next, you need to slow the idle speed down.  Is there a separate adjustmant, other than the gas-pedal linkage, that also opens up the throttle?  Do you have a "fast-idle kickdown solenoid"?  That would keep the RPM's up, until the engine gets to a certain temp, then de-energizes to allow the RPM's to drop.