Dave1983birdy

No matter how many things I replace on this 1983 firebird of
Mine it still is eating up gas like no tomorrow. I got my 4 barrel Rochester quadrajet tuned up, replaced the O2 sensor and throttle position sensor (did that myself which was fun) replaced the purge valve, distributor cap and rotor still need to do wires and spark plugs but otherwise she idles great drives great it's just even being a v8 I drive 30 miles from having a full tank of gas and I'm already almost down to half a tank. Someone help I'd hate to get rid of this beautiful car cause I can't afford to put in 60 bucks or more for gas every week when I don't even drive very that far at all to begin with. But if I can't fix this problem it may come down to selling it sadly so help!!

Dave1983birdy

Also replaced air filter and recent oil change as well

ploegi

Is your gas gauge accurate?

Try calculating your MPG, and post up those numbers. Even on my carbed V-8, I was able to do close to 20 MPG just cruising easy to/from work.

Dave1983birdy

I'm not entirely sure how to do that. But I know I don't get like 20mpg it's so bad

naf

iTrader: (7)

Calculate your mileage by completely filling the tank, record the miles, drive until near empty, refill. Determine miles driven since last filled and divide by the number of gallons you just put in.

Most common cause of low mpg in an lg4 that otherwise seems to drive fine is lack of closed loop operation. Best to determine that the car is going into closed loop, and if not, why. Best tool is a scanner that can read the aldl info 'live'. Try to get hold of one, preferably after the plugs, wires, cap and rotor has been replaced.

Dave1983birdy

I'm getting my car looked at Thursday cause the check engine light came on for code 45. What is that code again is it for the O2 sensor? I got the carb tuned by these mechanics who I always go to and they said the O2 sensor may need to be replaced but I just put a brand new one in as well as the purge valve so I'm not sure what could be making it run rich still. I know the O2 sensors don't work a lot of the time so I guess it could be that but I'm not too sure. Also I'll know the results of how many miles per gallon I get by Wednesday I filled it up Friday and I'm almost out already so I'm anticipating it'll be empty by Wednesday and I'll have those results then

Dave1983birdy

Okay just found out I'm only getting 10 mpg I couldn't even drive 200 miles before I had to fill up so I know that's bad even for a firebird. Someone help! What can I do

Keoman

iTrader: (3)

Does the quadrajet have a power valve?
We put the wrong power valve in a buddies car once, ate up damn near a quarter tank of gas in no time on a short test drive.
How do your spark plugs look? Pictures?

naf

iTrader: (7)

Mixture control solenoid, no power valve on non exports.

Scan tool show closed loop?

Bob88GTA

iTrader: (2)

You meant CLOSED loop, right?

naf

iTrader: (7)

crap.

fixed.

Dave1983birdy

Well I'm getting about 10.25 mpg with my car I have no idea why I drove 123 miles before I had to fill up. Code 45 is coming up even though I replaced the tps, tuned the carb, put in a new O2 sensor, and purge valve, new rotor and distributor cap. Doing the spark plugs and wires Sunday but that's not gonna make the code go away so I have no idea what to do. It's at the shop now hopefully they'll find what's eating up my gas

novaderrik

how is it running, other than using all that gas?

where is the timing set? those smogger motors came with the timing set way retarded and wake up and run a lit better with more timing. shoot for 10btdc.

how much slop is in the timing chain? check it by bringing the mark on the balancer up to tdc on the pointer and seeing how far you can turn it by hand before it gets hard to turn- a couple of degrees is fine, more than that is a worn timing chain, which means retarded cam timing, which means a loss of low end power, which means less fuel economy.

it's also possible that the cam itself is going flat, which is pretty normal for 70's and 80's engines with modern oils.

is the catalytic converter plugged? it will get really, really hot if it is..

Dave1983birdy

I don't know how to check the timing and stuff like that so I guess I'll have to go to a mechanic since I doubt my father knows how to as well. And Okay well I replaced my plugs and wires and honestly I've driven like 69 miles and I've lost like a quarter of a tank already and the code 45 is still coming on. If I can't fix this problem soon I'm gonna have to sell my car and I really don't want it to come to that so any suggestions on what I should get checked now would be greatly appreciated!!

8t2 z-chev

check the hardline fitting at the fuel pump to make sure it is not leaking gas- many years ago,got my line on a little crooked and it was leaking a steady drip-drip-drip,car got pretty bad mileage until I noticed the leak and fixed it.Once my O2 sensor wire got knocked loose,and though the CEL was on,did not really affect mileage that much...I get ~20 MPG with my CFI 350,my '85 f150 351w gets ~15.

Dave1983birdy

I had my car up in the air to look to see if anything was leaking yesterday. It's leaking a little bit of coolant I just need to replace the thermostat housing which is no biggy and a little bit of oil leaks but it's an easy fix as well. It's not leaking anything else though the mechanic said it all looks good so I don't think that is the problem

Dave1983birdy

O2 sensor is fine as well I replaced it like a month ago

cosmick

Probably need to pull the carb, check for leaks. When you remove the baseplate off the bottom of many Q-Jets, you'll see 2 epoxied plugs in the bottom of the mid section, those usually leak.

Dave1983birdy

When I got my carb tuned last month I told them to look for leaks and they pulled it up and didn't find any leaks anywhere from the carb. And when I did the tps and changed the gasket for the carb it was very clean looked like it was redone recently so nothing is leaking there

oil pan 4

iTrader: (1)

With an LG4, stock 1405 edelbrock 600, TH700 with no lockup and 3.08 gears I was getting over 20mpg on the highway as long as I kept it under 80.
Toss the Q-jet.

Dave1983birdy

I can't just toss it and buy a new one I'm low on funds haha I'm a college student. I need to figure out what the problem is and fix it asap and then once I graduate and work full time that carb will be tossed. I just don't know why it's so bad in gas. Just got the spark plugs and wires put in. And calculated how much gas it ate from when I filled it up to when I ran out and it was exactly the same with 123 miles from full till empty. ****en ridiculous

oil pan 4

iTrader: (1)

That's really bad.
I have seen used edelbrock performer carbs go for as little as $100.
New they are over $300.
Problem is these days no one really works on carbs any more and finding someone to do work on them is pretty difficult.

Dave1983birdy

Well I've just been told they're that much maybe you're right though. Where do I even look to buy one I have no idea. If it's my carb that's the problem with eating up my gas and giving me 10 miles to the gallon then maybe I should buy a used one that's better then mine. And maybe a double barrel instead of a 4 barrel like the one I have on it now.

Night rider327

iTrader: (13)

I got a used stock CCC (E4MC) Q jet from a running 1984 Z28 305 parts car I'll sell and I got 2 edelbrock 600cfm carbs that I'm rebuilding right now. I got a vid of the '84 z28 running. PM me if your interested

Dave1983birdy

Well I wouldn't want another quadrajet really everyone just tells me they suck I'd want a Rochester or something like that.

Dave1983birdy

How much for the edelbrock when you're done

Night rider327

iTrader: (13)

Rochester is the maker of the quadrajet.

I'll take $125 plus shipping on the Edelbrock when I'm finished with it. Both of the edelbrocks I have are 600 cfm man. choke carbs

a62belair

My Q-Jet was bad when I bought my 87. I was getting around that mileage, too. I replaced the carb and distributor with Edlelbrock 600 and aftermarket HEI, along with the manifold (I had to do the manifold, unfortunately, many broken/seized studs-bolts).
I also bypassed the converter lockup with a switch on the console (another necessity!). Now I'm around 24 hwy...
Then I changed to 3:45 rear gears- but still averaging 20 or (slightly)better...

Dave1983birdy

Well Ima take my car to the mechanic Thursday and see if my carb is the reason it's eating up gas and if it is then I may just buy an edlebrock. Like
I said I'm a student working part time so I don't wanna put a ton of work into this I already need new tires and I don't have much as it is but I need this car to be atleast decent on gas so I can use it as my daily driver otherwise I'm gonna have to sell it

naf

iTrader: (7)

converting to another carb will also require swapping the computer controlled dist for a mechanical/vacuum dist. Not a huge deal by itself, but will add ~$100 to the cost.

before going further examine the two wire connector to the coolant temperature sensor that goes into the thermostat housing on the front of the intake manifold. loss of connectivity here will keep the ecm from ever knowing the motor is at operating temp and it will stay in warm-up mode. these connectors take a beating over time on lg4's.

Dave1983birdy

Okay so actually I had to replace the thermostat, the thermostat housing, and that sensor you mentioned they were all bad. And when I replaced it all the code 45 went away and no other codes are coming up. So now I have to track my gas mileage again but do you guys actually think it's gonna be better now that the code is gone and I replaced that sensor and thermostat and housing?

naf

iTrader: (7)

Better yes. Fixed idk...

Dave1983birdy

Well I mean there's no other codes coming up now, and there has been since I bought it and have been having gas problems over three months ago so I think that was why it was eating gas like crazy. Atleast I hope it was the reason why and I don't have to do anything else to it.

cosmick

Is there a steam hole in the new thermostat? If not, I'd pull it and drill one.

GTA88

Dave1983birdy,

Did the new CTS and thermostat improve your gas mileage? Curious minds want to know!