Half tank 70 miles

[shsaint]

I have replaced
Spark plugs(ngk, iradium) + wires + cap
air filter
fuel filter
used choke/ carb cleaning of trottle body, little bit of intake manifold
changed my oil(silly but did so anyway)
checked all exhaust for leaks

let's see uhm....well my warms idle goes at 900 rpm
i just couldn't find my reason why my mpg goes down that bad
and so sudden. let's see,
i check my spark plug and found carbons around the rings and inside
which means that
my engine is running rich on gas.....

2 things that i think might be wrong uhm...
timing probably needs to be adjusted
coolant sensor need to be replaced
(the sensor that goes on top of the wateroutlet that flows from the radiator to the engine, and the has 2 long easy breakable green/blue tube on top)

anybody know what eles can be wrong?
my mpg is killing me 80-70 for half tank(city)

[nialusa]

Have you changed petrol stations? I find my Celica does better on some brands of petrol than others.

Try resetting the ECU, I had similar bad fueling till someone suggested reseting the ECU. I got a 200% increase in fuel economy after doing that.

You could try bridging the coolant sensor with a bit of wire. Also newer Celicas retard the timing to protect the engine when something is wrong, not sure if the older ones do that.

[SigmaProjects]

my guess would either the O2 sensors or valves, but your valves can't be that badly out of adjustment. Myabe a combo of both. You're probably going to need your O2 sensores to be checked out.

[shsaint]

getting new o2 sesnors(1 wire)...
i hope that helps.....
what's funny is that my car has the California
sensor(2 wire one) located below the main o2 sensor, i hope i don't have to replace that too.
valve adjustment is expensive i'll see if the new o2 sensor improve + the overnight reset of ecu

[SigmaProjects]

is your engine DOHC or SOHC? If it's SOHC it's fairly easy since your cams should be pointing right at you. Just find a buddy to help you with the process, it's pretty easy actually, just need large wrench for the crank, smaller wrenches for the valves and a feeler gage. Of course you'll need to find out what is suitable gaping for your engine. But it's nothing that hard.

[shsaint]

my o2 sensor arrived yesterday.
What a fix, and it only cost me 13 bucks
for that new o2 sensor (ebay)
I reset my ecu(overnight) and put on that new o2 sensor
Guess what guys...now my get 190 miles at half the tank
instead of 70 miles... WOW
i'm cured!!!!!!! thanks to everybody who helped me get thru this.

[Genesisfactor]

O2 senser huh...i got my celica thursday and i already put in 15 in gas to go about MAYBE 70 miles...good calll everyone. Thanks!

[barkroc2]

how to reset the ecu??????

[nialusa]

Originally Posted by barkroc2

how to reset the ecu??????

pull out the ECU fuse and leave it for an 30 mins/hour, put it back in.

[Genesisfactor]

Celica newbie-> how many miles are you supposed to get for a full tank? I have a 89 GT auto.

[nialusa]

I get about 260 miles to a full tank, you should get maybe 400 miles in a non-turbo car, mixed driving.

[Genesisfactor]

Originally Posted by nialusa

I get about 260 miles to a full tank, you should get maybe 400 miles in a non-turbo car, mixed driving.

Hmm...i hope so. I'm low on cash and it says that its 5/8ths full at 130 something miles. I hope i can squeeze out another 70 from that little bit, but it doesn't seem likely. It would be great to have a 400 mile car :-D. Esp since i don't have my job yet.

[skaterblader23]

woh wtf...im getting only 200 miles to a full tank of gas..,

oh this is bad. If im suppose to get around 400 then wtf is wrong. I reset my ecu and got a small increase *(about 40miles) but what else is there...the spark plugs are new, new distributor cap, new intake filter (sqaure).

I need to check the air filter but what else should i check?

I have a 1990 Toyota Celica ST so i know i should be getting around 350 miles.

[skaterblader23]

Air sensor***

[nialusa]

Celica`s are covered in sensors, when any one of them goes wrong or detects a problem it retards the timing and puts the engine into kind of a "safe" running mode. check your error codes if its possible to do that on a 1990ST? Not sure if you have a Knock sensor on the ST model (its behind cylinder 3) but they are prone to going wrong and will f-up your fueling.