Well, I am dumbfounded. I am getting about 11 mpg city driving, soft city driving that is (it was hard to do, but I did it for 2 weeks!). Now, I have the L03 in a 91 RS with 2.73 (right?) rear end. I am not positive it is still stock, but I am pretty sure it is. All new ignition components. The only thing I could think of is if it has non-stock gears (i cannot check, floor jack broke). Maybe the guy b4 bumped fuel pressure up? Also, I dunno, how could I tell if I got a clogged cat? Thanx fer any help - I cannot afford 11mpg!

 

Hey man, I know exactly how you feel, I can not help you with anything, but I have the exact same car, and I get about the same millage, all I can do is sympathise. if that's how you spell it. Talk to me if you ever find out how to help with the gas.

 

An easy way to check your gears. Do 70mph in D. Say your tach reads 2730 rpms that = 2:73 and so on. But still, 11mpg is horrible.

 

not a bad idea - wish I would thought of it today. I did about 50 freeway miles this afternoon (yes, I did let my self enjoy them! )

 

Someone, in another post, said O2 sensor. Maybe, but would it throw a code, or just give bad data? Also, would a stuck (or some other way closed) EGR do it?

 

A blocked EGR wouldn't do that I would think. When I had the 305 and emissions stuff, my brother took off the EGR and blocked it off. I was getting 14 mpg w/o OD.

 

Well, maybe next week (I got it off from school) I'll replace my O2 sensor, and do my ball joints (hopefully..).

 

I just figured out my MPG in the city. I was surprised to get 18 MPG in my well taken care of 1988 L98 GTA with 3.73 gearing. I don't want to figure out my highway driving, I know it is horrible.

I replaced last spring the spark plugs with Bosch Platinum +4's, the O2 sensor, general tune up stuff, and the car already has a Crane Fireball HI-6 ignition, which I believe contributes to a increase in MPG. The car also has a fuel pressure regulator which I suspect as tuned a little rich, I'm going to test it next month for fuel pressure.

 

Do they sell FP guages for TBI's? I think I am running rish also (but then again, maybe O2 sensor could cuasew that...)

 

11 mpg? Whoa, that is low. I have the same car and I get about 21.5 mpg with a combination of city and highway miles. I don't drive it soft either. I was getting 24 mpg when my car was younger.

 

oooohhhhh......this sux!

 

11 MPG sounds really low. My buddy had a RS like yours and he got almost 20MPG in town. O2 sensor probably needs replaced. When your car is sitting at idle, does the exhaust smell like gas. That's a good sign you are running rich. The O2 sensor can give false reading without throwing a code. You said it has all new ignition, was the mileage that bad before you replaced the ignition? When you say you replaced the ignition, what all did you replace? Have you checked your timing? If your timing is off, it will affect your mileage. Don't forget to unplug the single wire connector to set the timing. It won't work if you don't unplug it. What it does is bypass the computer timing control to set the base timing. I learned that one the hard way on my buddy's 89 Firebird.

Plugged exhaust could be a cause. Plugged cat, partially colapsed muffler. I don't think your car has one, but look for a vacuum modulator where the exhaust manifolds meet the Y-pipe. My 87 Monte Carlo SS has a carb and a preheat valve in the passenger side exhaust manifold. When the engine was cold the valve would shut, thus blocking exhaust flow on the passenger side of the engine. It was vacuum operated, and the only thing you see is the vacuum modulator/operator. Mine was sticking partially closed all the time. Now it is permanently open. Good luck.

 

wow Sparkee! As for my ignition - I repleced the wires (with Bosch what ever), plugs (bosch Platnuim (NOT +4)), cap/rotor, pick up coil, ignition coil. I do believe that mytiming is skewed somewhat though. I doubt I have a plugged up exhuast as it billows out real nice when its cold!
Also, I plan on replacing o2 sensor soon. Would Autozone/Murry's/NAPA carry em? Cheap?
One more thing - about timing - Chiltons says to use a inductive pick-up timing light. I have 'the other type'. Would that be a problem? Thanks for all the great responses so far!

 

I have an old "other type" that uses a spring between the plug and wire to connect the timing light. It should work fine as long as that spring doesn't touch the exhaust manifolds or any other ground. Like I mentioned before, don't forget to unplug the 1 wire connector. The wire is usually brown with black stripe. The only thing you haven't replaced in the ignition is the ignition module in the distributor, but that may not be the problem.

You should be able to get the 02 sensor at most car parts stores. I recommend either Bosch or AC delco for the best quality, but any one will work. I don't know about cost. I have seen sensors as cheap as $35 and as high as $90, depending on the car. Your's should be about $50-60.

As far as exhaust goes, you can have a partially plugged exhaust. It will let some exhaust out, but not all of it at high RPM's. The way I use to tell is use a fuel pressure gage with an adapter and connect it to the Air tube at the exhaust manifold. I forget the number, but I think it has to be less than 2-3psi at 3500 rpm. good luck.

 

what do you mean by ? Are you talking about putting it in 'field service mde' like chiltons says to do when setting base timing? Also, I replaced both the ignition coil (external) and the pickup coil (the ne INSIDE distributor). Wow, thats quite a bit for a sensor, is there anyway to test mine first?

 

You should be getting 17-20 city. I average 18.4 city, and 25 highway with my stock 305 TBI.

 

Field service mode, diagnostic mode, etc. that's all the same thing. So yes, do what the Chiltons manual tells you. With your car being a '91, you probably have over 90,000 miles, and if the 02 sensor has never been replaced then it is probably bad. It may seem like alot of money, but it is a necessary evil. Call some local parts stores, they might be able to find you a cheaper one. Look at it this way, when it's fixed, your gas mileage will about double, so you will be spending less money on gas. Good luck and let me know if it works or not. Later

Matt

 

***, I hope it works.
And, actaully - I got about 50k on motor. (130k on car...) I guess the dealer the guy b4 me bought it from dropped a new L03 in fer some reason...

 

I have the exact same car and got an 02 sensor for $25 at NAPA.

 

i have a 1988 LO3 with 103k miles on it and i get ~18 in town and 24ish on the highway. a full tank of gas lasts me 2 weeks if im easy on it and i drive to school and work everyday and then go mess around. i do have new plugs, wires, cap, rotor, coil and my car is pretty well kept so im sure that helps. also i hear removing the cat will give you alittle extra milage. im about to when i get around to it

 

Well, I rolled my ankle (I hope, feels different than a roll) last night. So I dunno what I can do over the next week (winter break). Yeah, this freaking sux - screwed all my plans (O2, Ball joints...). :nono: