ok everybody I'm fed up! I have an L98 motor in my transam and I get about 14mpg(mainly highway driving) and I've been reading on here that everybody gets about 19!! what oculd be wrong in my car that I get such crappy milage? the car runs fine(or seems to be) would a higher voltage coil or something give me better gas milage? thanks for the help

 

I get 17-18 and that's with a non lock up converter. Make sure your tires are inflated properly.

 

ya everything is in specs. the only thing that I can figure is that is has to be something with igniton maybe? is that possible that it would get that bad of gas milage because of that?

 

whats your a/f ratio doing while you drive? i get 18 mpg average every take with 50% freeway and 50% city driving. personally i feel i can find somemore mpgs yet to be had. i'm going to install my a/f guage and see why i keep popping lean codes when the O2 is new, seems like i may not be going closed loop.

i did the basic tune up when i got the car, t/b manifold cleaning, all fluids and filters, new O2, plugs/wires, new cap/rotor. mpg went up slightly but i still get a lean code cresting hills at times.

 

I'm currently averaging (city/highway) 14.5 MPG in my 92RS, with 300HP crate motor and TBI/5 speed,3.08 rear gear.
-Rich-

 

Thats one up on me. I get approx. 10 mpg. But then again, I drive trips of about 3-7 miles, and I refuse to drive with out letting my car warm up at least a little. That coupled with the fact I believe my ECM is only getting an inttermittent temp reading...

 

hey turtle - ya I've done everything that you have except wires, new cap/rotor. and I don't throw a lean code ever. and I o2 sensor is working fine, once I'm in closed loop its going between .48v to .5v which I've heard that is waht it should be. maybe new plug wires,cap, rotor and and afpr will help?

 

fuel system cleaner, check cap/rotor and test the coil, then make sure you dont have any extra drag from a bad wheel bearing or sticking pads. if i was getting 14 or less mpg i would be out going over my entire car on a daily basis until that mpg came up. i dont even consider 18 mpg to be decent even for a 350 auto. i've gotten as high as 30's+ from stick 302's on the freeway so 12 mpg loss is not acceptable.

 

ok I"ve done the fuel system cleaner(twice) and all the bearings are new same with the brakes and I don't think they are dragging because it is SUPER easy to push. I've cleaned the cap and distributor up. could the coil being bad or cap/rotor make THAT big of difference? also what about plug wires? thank you for your help

 

yup it can effect the performance of the car, test all your ignition components, check the plug gap and wires resistance. there has to be a reason you are flushing some mileage somewhere. i have had a intermitent plug wire before that kind the running ability of the motor but not mileage.

i've already replaced everything but the kitchen sink at this point as part of a new car tune up. if it even looks old i replace it, wether its still good or not.

oh have you checked the cat? as they start to plug you loose performance and mpg.

 

yes the cat. is fine. I have actually taken it off, before I did that I was getting about 12mpg so taking if off helped some. then plugs have about 2500miles on them and were all gapped at .35. I'm thinking about replacing the wires,cap,rotor and coil to see if that helps.

 

also how do I check the wires resistance? I've never had and igniton problem with any of my cars, so I've never learned how :-) thanks agian for you time turtle

 

you need a volt meter to test the resistance, if the wires are old just replace them anyway to be safe. a wire can look and performance great even passing a resistance test but bit the dust in 2 seconds, had that happen too.

 

I think that I'm going to replace the wires and coil here, see if that helps. hopefully it will