i've been getting like 12 miles to the gallon in my stock 94 trans am a4 in city driving. I didn't have a heavy foot with this tank and the gas mileage was still around 12. What could be causing this?

 

Damn thats worse them my 900hp camaro
Start from the basic's plugs wires air filter. Then move on to more technical, like 02 sensors, coolant temp sensor.

 

A coolant temp sensor could really cause that?

 

Don't forget the fuel filter.

 

My TA had the same problem, driving like an old lady and no better than 13. I changed just about everything, plugs, wires, opti, fuel pressure regulator, fuel filter(all those needed it, needed a tune-up when I bought it), I put headers on, and I still could only manage maybe 14. Then I ditched my Flowmaster(the name is fitting ) and put on a SLP dual/dual muffler on a couple weeks ago and my gas mileage is now about 16 driving it like it was meant to be driven. So who knows, you may have a problem like mine, just a crappy clogged muffler. Good luck, hope you can figure that one out.

Tom

 

houston i think we found the prob. might have to change this flowless muffler i got.

 

I don't think that your flowmaster is the problem. I don't know why everyone hates flowmaster so much I love mine. Ofcourse I don't have any cats so it sounds a lot better than someone with cats. Do you have cats? If so, than that might be your problem. They could be clogged up. Do what sleeperz28 said and start with your plugs, wires, etc.. and then go from there. I just did my plugs and wires and now I am averaging a little over 20mpg city/highway.

 

yeah I been battling a bad gas mileage prob myself....used to have decent mileage, but it dropped to about 12-13 mpg city now. did all the tune-up related things, cleaned maf, added slp cai, fuel filter, plugs, wires, tested fuel pressure, hooked my autotap up and nothing I can see out of the ordinary, no misfires, no knock, o2 voltage is what it should be....I've been leaning towards my cats or some restriction in my exhaust, but I havent had the time/money to test it, let me know how urs turns out thanks!

 

yea i got some gas mileage problems i get from 11-14 14 being highway and 11 being stop and go real fast

but ive changed fuel filter, and air filter 3 of my 8 sparks... cant reallly get to the rest

but other then that im stumped... besides my car suxs after its warm 1000-2000 rpms suck and 5000-redline is kind of powerless

 

MAP sensor....

 

If you coolant temp sensor is bad it will show a reading of -6 degrees not allowing for closed loop. I have a big problem with the connection on mine, the connecter has to be placed on half way to read correctly.(make propar contact) if your car is in open loop your constantly running warm up enrichment=bad gas milage. The only way to find a problem is with a scan tool that provideds feed back. I had the LT1 scanmaster some years ago and that worked great for me.