Pontiac Firebird 3.1 V6 needs high consumption

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valente

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Pontiac Firebird 3.1 V6 high consumption

Hi,

i own a pontiac firebird 3.v v6 built in 1991 3rd generation. It needs more than the double amount of fuel, that it should need, and i changed, checked a lot of parts, and still don't know where the problem is.
So i changed the air filter, changed the ingnition plugs, oil change, new oil filter, new cooling liquid, new thermostate.
When the car stands, but the engine is on, it will reach a temperature about 210 F (100 C) and when i start to drive, it goes back to about 194 F (90 C).
I don't know if that is norma or not, i can't find information about what temperature it should run on, but people told me that US-Cars run on higher temp. than european cars.
I never turned the AC on, so that can't be the reason for the high consumption.
Does anyone of you have an idea what i have to do/repair to have a normal fuel consumption? My car needs about 22-25 L / 100 Km (11-12 mpg), and should need about 12 (19 mpg)

Also the carbon monoxide level of the exhaust fumes reaches sometimes about 3% and sometimes its normal. So from my point of view the problem cant be the lambda, because the lambda values in the fumes are normal, and it cant be the catalytic converter, because if it would be damaged, the carbon monoxide should be high all times.
please tell me if you have any idea what could be the problem.

thank you very much
 
Last edited:
thanks for the answer

i will check these things out and will let you know when i found out what is wrong with the car.

can you recommend a computer to read out my errors that works fine for a firebird?
 
1991 Pontiac Firebird/Trans Am 6 cyl, 3.1 L, Automatic 4-spd,
Fuel Mileage
Unleaded Regular Gasoline:
City 16 MPG
Combined 19 MPG ( Average City / Highway)
Highway 25 MPG

1991 Pontiac Firebird/Trans Am 6 cyl, 3.1 L, Manual 5-spd,
Fuel Mileage
Unleaded Regular Gasoline:
City 15 MPG
Combined 18 MPG (Average City / Highway)
Highway 25 MPG

Doug in P.R.:cool:
 
I have the same problem, I've changed spark plugs, filters, oil probe CO, I've cleaned the whole intake system, and can not find the fault, someone knows what it might be.
Discussion of third generation have told me that it may be the fuel pressure valve, but this works well.
 
What is your miles per gallon and what year and what engine are your referring to? Did you check the computer for codes? Did you do a compression test? Did you remove the vacuum line going to the fuel pressure regulator and check for gasoline?
______________________________
 
neverending story

Hi all,

first of all: thank you for your input. it helped me a lot. so i continued to replace parts of the car. I changed the distributor itself, the spark cables, the distributor finger and the cap, as well as the dmc temperature sensor. So now it looks like the car has normal consumption, and the whole sound and driving experience is much smoother, because the distributor was really bad. but now i have a neew problem. whenever i hit the brakes the revolutions go down from nearly 1000 to about 500. sometimes even the engine goes of. that problem only exists when im not on the gas, as soon as i give a little bit gas, the car drives really smooth, but as soon as i leave the gas pedal the revolution goes up and down and it gets worse when i hit the brake. do you guys have any idea what the problem could be?

thank you in advance

Valente
 
check for a bad vacuum hose going to the brake booster.
 
Check the power brake booster and vacumn hoses for leaks.

Doug in P.R.:cool:
______________________________
 
Thanks guys,

so i chekced the vacuum hose for a leak but couldn't find any, and when the engine gets warm, it starts to go up and down with the rpm at idle state, also if i dont hit the brake.
im going to get it repaired at a garage because i dont have any clue where that problem comes from. i will inform you as soon as i know where and what the problem is.

thx
 
And by the way. Does anyone of you guys know if theres a possibility to download an owners manual for that car. Mine is not usable anymore and i am from austria its hard to get one here...
 
i cannt find any site that has a download for that manual
 
Shit

So now, after months of spending money and work into that car, he got a new setting for the whole ignition system i installed. and the fuel filter is new too.
So know the car works fine, the engine doesnt stop to work when i break and the engine runs fine.
but still the high consumption is there !!!!!!
Im really depressed, because i changed so much parts of that car, as i wrote before in all the posts, and still the car needs more than the double amount of fuel it should need.

does anyone of you has an ideo where the problem could be hidden?

thank you in advance

valente
______________________________
 
What type of driving are you doing mostly city or highway? On the highway what speed are you doing?
 
im driving mostly in the city. i drive really carefully and try to keap the consumption low. i dont have the air condition on, to save even more.

but i dont drive highway at all....
 
so have you actually measured the miles per gallon after all the work was done? The rating for the car in city driving was 16 mpg.
 
So i checked everything, and no garage could find anything bad at the car, every part works just fine.

but now, it still has a consumption by 13 miles per gallon.

i dont care anymore, it took me a lot of money to find out that there is "nothing" wrong with the car, so i just go on driving it with this high consumption.

thanks for all your help.

By the way i got some more questions:

1. There is this part made out of plastic an the inner side of the door with a cupholder integrated. Mine is broken, and its impossible to buy that part in austria. do you know where i can get it?

2. the same thing for the electrical antenna, mine is broken

3. Does anyone know why there are two different drive emblems at the automatic gearshift? there is one with a frame and one without. i dont have a manual and i couldnt find anything online.....

thanks
 
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