Really BAD gas mileage.

[Big Rectangular Car]

It's depressing.
I can't afford to drive my GM this way, it's getting somewhere between 5-7 mpg, right now, and I have been very light on the pedal, and at $3.36 a gallon??
I haven't gotten her tuned up yet, but I'm wondering if there's anything else that needs checking. Oxygen sensor? Fuel filter? (Usually that needs checking with cars like my VW, likely with the GM as well)

I really do need to get a repair manual...

[nitroracer]

Try the basic tune up first since you havent yet.

Spark plugs, wires if needed, air filter, oil filter, fuel filter (since its old), check for codes on the oxygen sensor(s).

[p71towny]

Dont forget cap and rotor along with pcv valve/screen. If you replace all of these things mentioned I guarantee your milage will increase double if not triple.

[pine box]

Since you have a blowby problem like I had on my '85, the FIRST thing you should do (if you haven't already) is replace the air filter, and clean the housing. I know you have already cleaned the PCV diaper. Always keep an eye on that.The oil will clog the filter, resulting in a too ritch mixture, which is hard on catylitic converters, o2 sensors, and your wallet. You may want to buy a K&N type oiled fabric filter, they don't clog like the paper ones do.
Then do the cap, rotor, etc.

[mrltd]

Do a complete tune up and get the timing checked. Make SURE THAT THE TIMING IS SET CORRECTLY! This means the timing is set at 10* BTDC with the spout connector removed. Also more than likely your converters are clogged from the engine running poorly.

[Big Rectangular Car]

Oh, yes, the converters. Forgot about those. Gah. I hope I don't have to get new ones...

Okay, I have it down, now, thanks to you all. I certainly hope the mpg triples!

[85crownHPP]

our O2 sensor is cheap - go ahead and replace it too.

[87mefull]

If you want to get good gas mileage, start cheap. 5 to 7 mpg sounds like a big problem, such as a vacumm leak, bad injectors, a fuel leak, or incorrect timing. I would check those first incase it ends up being a costly problem and sometimes its something simple. The plugs will also tell if your having some problems and how the mixture is also (lean/rich) and they are cheap to replace (motorcraft plugs were $1.50).

Buy a cheap code scanner and replace the correct sensor(s) first, some even diagonose timing problems also. I wouldn't replace the 02 sensor right away unless its original or shows it age, save it for last since its still $35 for one. You will still get codes for 02 sensors if the fuel/air mixture isn't right, which will be indicated by the plugs.

Also, don't waste your money on a haynes manual, heck I'll sell you mine for cheap since it has nothing for EEC-IV cars . You can also buy a chilton's manual on ebay for dirt cheap, I bought mine for 5 bucks and it wasn't a library reference copy (people rip the pages out of them). It has a ton of info on CFI panthers, more than you probably need. Another good manual to buy is the Ford EFI handbook (I don't know the name of it), but it may apply more to my car (EEC-IV) than yours.

[85crownHPP]

a CFI o2 sensor is much cheaper than a MPFI sensor, mine cost 18 bucks.

A bad vacuum leak is a good guess too, i forgot to mention that. Also make sure your tires arent low.

[gadget73]

I'll second, or third, or whatever, the vacuum leak thing. Make sure the hose to the MAP sensor is connected and in good shape. The whole thing will run totally whacked out if it isn't. Low vacuum = high load to the ECM, so it pumps out more fuel.

[Big Rectangular Car]

Hey again,

Yesterday I replaced 6 of the 8 plugs so far, (difficult for a couple areas to reach, and I'm not as young as I used to be, ha) I'll finish up this morning with my son helping out.
All the plugs showed a lot of wear, but 5 so far were the normal ashen color. One of the plugs was black, sooty but not oily, from the foremost driver's side cylinder. THey have at least 30K miles on them.
Also replaced nearly all the wires, have two left to go, and will replace the cap and rotor.
This car has so many wires and hoses on it, it looks like a prop for Star Trek, sheesh...
I found out yesterday what CFI really meant, central fuel injection. I was confused by the carburetor, and the fellow at the FLAPS said it was a combination of injection and carburetor, something like that. I had been wondering what those things were.
Bear with me, I'm used to either mid-70's Mopar products, or 80s VW products...
You learn something every day.

Update:
Finished up changing the plugs, wire, etc. and the plugs all looked ash grey, which I think is normal... all worn quite a lot. Just one plug was sootier than the rest.
Also replaced the PCV filter, they finally got those in. I looked at the PCV valve, and it looked like it had been recently replaced.
Started the car, and it was smooth, but it was smooth running before, so... *shrug*
Checked the vacuum hoses, they looked good, were firm but not brittle, and tight. There are a lot of them, so I may have missed some, but it doesn't seem to behave like there's any vacuum leaks.
When I drive the car on Sunday, I'll see how it goes. If the fuel gage needle doesn't move as fast as before, the I'll know I'm on the right track.

Oh yes, bought a Haynes manual, (better than nothing!) for a whopping $1.18 on Amazon, it's from a used bookseller. With shipping it will cost me less than $5. So, I think that's a good deal. :roll:
I'll be able to acquaint myself better with the car, and not ask quite so many dumb questions. LOL!

[gadget73]

Sounds good. New plugs and stuff can't hurt any. Hopefully it helps you out.

[N A]

Pick up any mileage?

[turbo2256b]

Plugs should be brown, tan, white combination. Grey is usualy rich. Check for slop in your timing chain too.

[88grandmarq]

Have you checked for trouble codes yet? doing so will point you in the right direction if there are any sensors being screwy.