Bowl_of_Rice

If you still see the thread i still have this problem

ok so i been getting pretty bad gas milage maybe like 16-17mpg

things ive changed
Spark plugs ngk g power
Wires ngk
NTK o2 sensor
Cap
Rotor
fuel filter
Ect sensor
timing belt
water pump
new thermostat
swapped in new injectors just to see if there was a difference no difference
2 bottles of sea foam
Cleaned iacv
Bleed coolant until no more air was left
ive done more just trying to remember i did a lot

when i drive the car the gas needle stays still but when i park the car then itll drop when im going around a turn fast or you know just turning the needle will drop then go back up and also my idle has been pretty weird too, when im coming from a stop sometimes itll start idling so low that itll want to stall until i come to a complete stop, when it doesnt do that itll just fluctuate every once in a while, ive noticed that im getting black soot on my bumper so i guess im still running rich? but what else would cause me to run rich, i can smell my cat sometimes but not all the time, i can smell gas in my car when i have the heat on or sometimes when i have the windows down, help me out honda-tech with these gas prices going up i need my car to start getting the gas milage it should be getting

el crapitan

it's normal to get poor mileage in the winter. as for your temp readings, maybe the t stat is stuck open

Bowl_of_Rice

thats what i was thinking but idk its cheap so ill just replace it and see whats going on, my heat is great so idk my car is weird lol

Targa250R

If the engine is constantly running below the normal operating temperature, it will wreak havoc on your fuel economy. The fuel maps are based on coolant temperature since the engine requires a rich mixture to run properly when cold. If the ECT sensor is telling the ECM that the car hasn't reached operating temperature yet, it will just continue to dump too much fuel and never leave open loop.

I'd suggest starting by replacing the thermostat with a Honda OE two-stage replacement thermostat. Do not buy one of those single-stage Stant thermostats from a chain parts store; they rarely work properly and often cause more cooling problems than they solve.

Bowl_of_Rice

thanks for the info bro. as soon as the weather gets a little warmer ill drain my coolant and get an oem t-stat and 50/50 coolant and see whats up

PatrickGSR94

iTrader: (1)

It's not normal for it to be THAT bad. I regularly get 26-28 mpg in the city on my daily commute, in my 300K mile GS-R. I agree that the thermostat is most certainly the cause of the problem.

Bowl_of_Rice

i thought the thermostat is what gives you heat and tells the ecu that the car is cold or warm but i know now that theres an electronic coolant temperature sensor and another sensor that goes to the cluster that tells the temperature i guess i was wrong

Targa250R

The thermostat is a mechanical valve that prevents the coolant from circulating through the system when cold, then allows the coolant to circulate when hot. It does not have a connection to the ECM at all.

If the coolant is cold, the thermostat is closed and the coolant will not move from the engine to the radiator and then back to the water pump. Once the coolant heats up to a certain temperature, the thermostat opens itself up and the coolant gets pumped through the system (including through the heater core if the heater valve is open). If the coolant temperature drops back down below the the threshold temperature, the thermostat will close itself back up to allow the coolant to absorb more heat from the engine.

If the thermostat is faulty and sticking open, the coolant will be flowing through the radiator constantly and cooling too much, so it won't heat up to proper operating temp or it will take a very long time to reach operating temp.

You are correct that there are two coolant temp sensors - the smaller single pin sensor sends a reading to the temperature gauge only. The larger two-pin "ECT" or "TW" sensor sends a reading to the ECM.

wezzel19

dont forget tire pressure! just for good measure 35psi front 33psi rear stock recomendation...it helps me out a lot

IN VTEC

iTrader: (3)

My suggestion is to check the ignition timing. Retarded timing can cause low idle and poor gas mileage.

You can usually tell if the thermostat is constantly open by looking at the coolant temp gauge. If it's not getting anywhere near the quarter to half then it's either the thermostat or the gauge cluster sensor.

1998GsRIntegra

Have you checked to make sure the O2 sensors are still good?

el crapitan

ye, i guess i should have done the conversion before making that statement. i'm in canada, so km/l.
ditto though on the engine running below normal operating temp being a possible cause of poor mileage

Targa250R

An oxygen sensor will throw a Check Engine light long before the fuel consumption is affected that much.

Bowl_of_Rice

i forgot to say i have a brand new o2 ntk sensor

PatrickGSR94

iTrader: (1)

No it won't. I have NEVER had a trouble code related to the O2 sensor. Yet when I replaced my original one with 250K on it, my highway fuel economy jumped a good 3-4 mpg. My brother's old del Sol was the same way when he put in a new one. I need to put a new one in our Corolla with 220K on it because I know it will make a noticeable difference in that car's fuel economy.

Bowl_of_Rice

i think my iacv is bad when i unplug it while the car is running itll shut off

PatrickGSR94

iTrader: (1)

Isn't it supposed to do that if you unplug it? I would think that if you unplugged it with engine running, and there was no change in engine idle, then it would be bad.

Laserjock

Additionally, if the ECU is fooled into open loop mode so it will inject fuel at a pre-determined rich condition (like on cold engine)

It will switch to closed mode (the ECU will adjust fuel flow for best performance/ economy) when it determines by the coolant temp (and other inputs) that the engine is up to working temperature.

Replace your O2 sensor(s) if you are not sure of age

Check and adjust tire pressures

Have an alignment done

Your idle indicates a leak in the intake manifold area or a bad IACV if you've cleaned it already

95 GSR = 33MPG on my 1st tank this week!

Targa250R

Key words: "that much."

A narrow-band heated oxygen sensor doesn't have the range to affect the fuel economy by 10+mpg. The sensor is just a source of feedback for the PGM-FI control system and is not absolutely necessary to run the engine, so it has a limited effect on the fuel maps when in closed loop (and obviously none in open loop). If the voltage is going off the charts, the computer will suspect a problem and throw a code rather than adjust the fuel maps based on the erratic signal.

Restoring 3-4 mpg to bring the car back up to an average of around 28-30 mpg (a 10-14% improvement) would be within the normal realm of replacing an old oxygen sensor. A 10-12 mpg difference (33-43%) would not. Of course, an O2 sensor can be just one out of several factors that are adding up to cause a bigger problem, but it won't be the lone culprit.

PatrickGSR94

iTrader: (1)

ah, well, when I replaced mine I immediately broke my highway MPG record by getting 36.x mpg on a highway trip, just a few days after replacing it. It was probably around a 10-12% improvement, but to me that is huge.

1998GsRIntegra

The car should still run with it unplugged. It will just idle at like 200rpm.

vtecdc4

check fuel injectors for gas mileage?

Laserjock

didn't know injectors came with odometers :p

Targa250R

That doesn't necessarily mean that the IAC valve is bad.

The idle speed should drop - or, if the base idle is set too low, the engine will stall - if the IAC valve is unplugged. If there is no change in idle speed, then the valve is bad and should be replaced as Patrick stated.

Your idle fluctuation may be related to the temperature gauge fluctuations, which I suspect are being caused by a stuck thermostat. If the IAC and/or FIT valves have alternating currents of hot and cold coolant running through them, they are going to adjust the idle erratically.

I also suspect that your base idle may be set improperly if the idle drops low when coming to a stop and the engine stalls when disconnecting the IAC valve. Proper idle speed is 750 RPM plus or minus 50 RPM. If your car isn't idling between 700 and 800 RPM at operating temperature (between 176-212 F), then it needs to be adjusted. If it is never reaching operating temperature, well then you can't check or set the idle speed correctly

Bowl_of_Rice

Thank you everyone for giving me helpful information. Im going to get a new thermostat this weekend and some new 50/50 coolant and let everyone know whats up hopefully everything will be fine.

Is there a diy for it anywhere? on honda-tech or teamintegra