You said the 02 sensor is new... Is it factory Toyota or aftermarket? I ran into a problem on an 85 Toyota 22re w/ a bad sensor, so I threw new one at it. Mileage was HORRIBLE after. Turns out the aftermarket sensor was 1/2" shorter than the factory sensor and didn't even get into the exhuast stream.. So the computer was all confused and dumping tons of fuel in to compensate.

Worth a check if it's aftermarket... if it's factory Toy... then I don't know what to tell ya.

I've heard the horror stores about aftermarket... It's OE identical. Same company, same size, same everything.

But thanks for the suggestion.

Have you verified that the vacuum and centrical
advance are working properly inside the distributer?
They can get gummed up. Mine did. When I corrected
that, my highway mileage went from 19 to 23 <img src="/forums/images/graemlins/smile.gif" alt="" />

Are there any exhaust leaks in the exhaust line?
My Carsound Cat blew one of it's welds and my gas milage went down to about 10-12mpg.
I rewelded the line and it went right back up to 19 mpg.

You know, the vacuum advance feels kind of gritty, like whatever that fiberglass looking thing is is disintegrating and gumming it up.

A) What is that thing?
B) Can it be replaced?

The distributor looks OK otherwise, no real play in the shaft, and the governor advance still feels fine.

*EDIT*

Heh, duh. Just an insulator. I pulled it off and repainted it, and shot about half a can of brake cleaner in there to try to clear everything out. We'll see.

I removed my distributer from the motor to clean
it. The vacuum breaker plate should move with no
resistance. That assembly has to be removed to get
further down to the little weight-spring thingies.
Make sure they move freely. I used brake cleaner
(I think) to free it all up, and then some silicon
lubricant. Adjusted the gap while I was in there.
Make sure you start at TDC before removeing the
distributer (I assume you know that)

Well, here's an update:

Before I made the trip home (360 miles, all freeway), I played with the idle & timing some, didn't really change it.

I pulled 21MPG on the trip home, so city driving was most of the problem, BUT...

I did take it to the dealer for lube/oil/filter and a general lookover, and here is what they found:

1 ruptured diaphragm in the vacuum advance (I asked them to check)
1 small vacuum leak between the intake manifold and the head in the vicinity of the #4 cyl (found when they set the timing and idle)
Leaking cat to exhaust flange, I knew about that, and had them throw a new gasket in

So I guess the moral of the story is a lot can be attributed to city driving, but if your mileage drops, it's still a good idea to look into it.

Now I'm wondering how much it will improve when I fix the diaphragm and vacuum leak... if I can pull 21MPG doing 75-80 on I5 with those problems and an exhaust leak, I can only wonder what it will do afterwards.

Thanks to everyone for all the helpful ideas and good suggestions. This board continues to be the greatest resource for shadetree mechanics I've ever found.

Cool; nice to know where to look for other trouble spots on these old ponies. Let us know what your gas mileage does once you're squared away.

Would a 92 truck has this vacuum advance on the distributor? Does anybody have a picture of it?

Thanks

The round gold colored thing directly under the hand in the picture is what you're looking for.