Hello! I'm glad to announce that I finally got my Bonny up and running. It'* a charm! But... It ate 15 gallons of premium gas in 147 miles. Ouch! Now then, I haven't raced it, or floored it or driven fast at all. Quiet the opposite since I'm checking it out (remember it was a salvage and I fixed it) I have checked for gas leaks both running and stopped with no results either outside or in the engine compartment. No gas smell either. No "rich" smell coming from the exhaust either.
There'* no pinging either.
I figure I must have a really bad O2 sensor and a really good catalytic converter since I can't detect the fumes.
Short of replacing: wires, O2 sensor, spark plugs...What else could be wrong?
Thanks in advance for your help.
I love my cars and I like working on them and I hate the fact that I can't find such an obvious thing! Guess I'm not such a good mechanic.

Wires, O2 sensor and plugs.

But at the same time, you may be getting too much TC slip. Or perhaps no TC lockup in OD?

Any lights on the dash? What rpm'* are you running at 55mph, cruise control set?

I'm at around 1600 rpm'* at 55 mph. Tried the cruise just to check. but don't use it
What'* TC Torque converter? I can feel the overdrive kick in and drop the rpm'* when I'm not pushing it.

A bad fuel pressure regulator can make you use too much fuel, also. With the engone off, take the cap off the fuel pressure test port on the fuel rail, and push in the needle. Do this after you've had the engine off for a while, and then turn the key but not so the engine starts, so the fuel pump runs for a second, then try again. If fuel sprays out, insetad of dribbles the first time, your regulator is probably bad. If it doesn't spray immediately after turning off the key, the pump could be bad. It helps to have some paper towels handy.

That said, my first guess would be the O2 sensor.

1600 seems a WEE bit too high for 55 mph with our gear ratio. I suspect you are getting some slip in TC lockup, which could contribute to low mileage. What does your trans fluid look, smell, and taste like? (forget the taste part.....look and smell will do).

Where is Calexico? WAY down south like it sounds, or up North? I'm asking because I have a scantool that can determine TC slip......when I get it back from DrJay in WA, we might be able to hook up and run through it all.

Ok, let'* see here. Suppose the car has been off for some hours. I take the cap off and press the needle (I assume this is to relieve any existing fuel pressure), Then turn the key to actuate the pump and try it again.If fuel sprays out then fuel regulator is bad, if it dribbles then the pump is bad. What is an OK condition? Sorry I got a bit confused.

Calexico, California (92231) 120 miles southeast from San Diego. Our office is located 1.2 miles from the border with Mexicali, Baja California< Mexico. We can go to Mexico for lunch and be back with a smile

My boss has a OBDII tester. Will that work with my car?
You're right. it'* 1500 (smack on the line) not 1600. Transmmission fluid seems fine. no smell or thinnes I can detect. But I'm sure it wouldn't hurt to change it.
Where'* the connection to put the OBD tester?

Thanks

OBD2 uses a 16-pin ALDL connector. Yours is 12.

You can retrieve codes using the procedure in Techinfo with nothing other than a paperclip, but you can't watch things happen realtime that way.

The scantool you're talking about MIGHT be able to work on your car if there'* a 12-pin GM cable available for it.

If it just dribbles the first time, regulator. If it just dribbles with the key turned, pump (not just kinda bad, but really bad, which I doubt if it runs at all).

The regulator isn't too bad if it sprays a few minutes after turning the car off, but not perfect. My old regulator would hold pressure for maybe five minutes then would just give a dribble. I replaced it, my MPG went up a few, and it will still spray hours later.

Checking the FPR by pressing the pressure valve on the fuel rail can be a bit misleading. GM fuel pumps are known to sometimes not hold pressure after shut down and leak down into the tank. This would give a false indication. The best way to check the FPR is to pull the vacuum hose off of it while the engine is running. If any fuel leaks out of the nipple, the FPR is bad.