I have a 88 SC TBI 305.....
im averaging 10 Miles per gallon......
its stock w/ just an open elment air
cleaner..... i bought an 02 censor for
it a month ago...should i relocate my
air temp censor to lean it out or something......i want to get 18-20 MPG
at least, 10 isnt cutting it it has 74k miles on it....what do i need to do?????
-----------------------------------
Speed
"speed kills but 55 can take an eternity"

 

I would double check the O2 install. Are you getting a Check Engine light?

If the O2 is fine, and no check engine light, then a basic tune up is all I know to do. Plugs, cap, rotor, wires, fuel filter, and an air filter.

I would start with those, and if still you are getting 10mpg, then maybe you have a faulty injector?

Good luck,

Thomas.

------------------
1992 RS Camaro - Red
305-TBI/5 Speed Manual- 3.08 geared rear
1.6 Roller Rockers / Open Air K&N Filter / TBI Spacer / ADS Super Chip & custom burned Off-Road Only chip /
Headers - 3" Cat'Back - Flow Master - Adjustable Coni shocks & struts / 16" factory wheels

 

Any fuel leaks/smells? Running rich (black smoke)? Transmission okay? No slipping, TCC locking up okay? Tire pressure good? Seized brakes/parking brakes (check if they're hot after a drive)? Check the plugs, too.

 

I have an 89 RS with the L03 305 TBI, 5-speed, blah blah blah... and I'm getting about 10 miles a gallon too, and i've replaced my distributor/cap/rotor, spark plugs/wires, fuel pump, fuel filter, fuel pressure regulator, cleaned out the TBI (rebuilt?), a new map sensor, new tps, new O2 sensor, new base gasket(with tbi rebuild), new clutch, and it still is getting 10 miles a gallon! The only thing I can think of is the injectors, which i probably should have replaced anyways, anyone else have any ideas? please help...

 

No check engine light i just relocated my IAT to a cooler place, O2 sensor is ok....how would i check the injector on TBI?? How much would 2 new ones cost?? My timing is set at 10* too...should i set it back a couple to 4-6*??



[This message has been edited by speedtendancy (edited December 13, 2001).]

 

Maybe try to replace the coolant sensor, that sometimes can cause real problems like bad gas mileage.

 

In addition to what has already been suggested make sure your EGR is working right and your CAT isn't plugged.

You can pick up flow matched injectors from TurboCity.com for a helfty price.

 

There are so many things that could cause bad gas mileage. Are you sure it only has 70k miles on it? I would definately go with a tuneup, like previously suggested.. The fuel filter can do so much for performance/economy.

I've got an 89 IROC with a 305TBI and I'm getting about 20mpg, but it's running so rich right now (bad fuel pressure regulator) that I'm blowing 10 times the legal amount of emissions out my exhaust. Anyways...

If the timing's too retarded, that can waste gas. If your engine never warms up properly, it'll waste gas pretty bad as well. Your thermostat might not be closing properly, and your engine overcooling. I prefer 180*, but it's personal preference I suppose. Certainly, don't go any lower than 160, and if you go that low you'd want to think about working on the chip some as well.

A slipping tranny will definatly reduce mileage, as suggested.

About the IAT sensor, I'd put it inside the air filter where it belongs. It's not going to make TOO big of a difference, no matter where you put it in the engine (unless you tape it to the block or something), but it's still just another thing for the computer to work with, and I'd want it getting accurate data.

Your injectors could be clogged/dirty.. There's places you can send them off to to have them cleaned/flow matched.. They're not THAT expensive, but you have to go without a car for a while, which always sucks.

 

I didn't think TBI's had MAP's..

 

Yeah, TBI cars have MAP sensors. That's how the computer measures the vacuum the engine pulls. That value is then used to meter fuel and control spark advance.

 

Yeah all GM TBI engines are speed density....

 

my 305 TBI was getting HORRIBLE milage probably less than 10mpg and i didnt know why...finally my fuel pump went completely out and i replaced it and after that i started getting twice the gas milage at least id say i get 18 in town right now and maybe 26 on the interstate...