Realy Bad Fuel Milage

[jftaylor]

Ok folks im starting to regret buying this car 98' grand am se 2.4l twin cam 238566kilometers auto, first ? when replacing sensors with new ones if a bad sensor gives a trouble code and i replace it with a new one does the computer pick up the new sensor or do i have to erace the trouble code from the old sensor in order for the computer to realize that there is a new sensor installed. Does compter trouble codes to to be eraced after new sensors are installed?

Next ? really bad fuel milage

Items Replaced

Fuel filter
Air filter
TPS
Coolent Sensor
O2 Sensor
Oil and filter change
trans fulid and filter change
Cylinder Head servised New HG, Bolts, etc.
New rotors and pads

what could be causeing my bad fuel milage brakes do not drag all wheels are free and tire pressure is right on. Would it be bad injectors, pressure regulator, when driving she is perfect and i do not drive her hard. often she will stall after i start her give her gas and sometimes she will not take the gas and shut off, start her again and she will be fine, really at wits end i do all my own work with the car, do understand all the jargin just trying to get some direction, is there anyone out there in Grand Am world experiance this and figured it out, if so would love for you to repley back.

Thanks Guys

[Blackhawk]

How about spark plugs and making sure your coils and the spark plug springs aren't rusted? Try some name-brand FI cleaner.

[rixGAphx]

Do computer trouble codes need to be erased after new sensors are installed?
No.

The PCM will *eventually* recognize that things are working well, and cancel the respective codes.
For TPS, O2, and ECT, the PCM will recognize and canel immediately if things are Ok.
If the problem remains, then the code will continually be reset.

If the code had something to do with the Evaporative Emissions Control, the PCM will wait 3 or 4 complete warm-up/cool-down driving cycles, with no sensing of problems, before it decides the system is actually free of defects.Next: Really bad fuel milageHow many miles per gallon?

Do the math and tell us.
Then read one of the monthly threads in this forum about 'What should my milage be?"
The GA gets crappy milage for such a small car, even with the little 4-bangers.


Items Replaced:
Fuel filter
Air filter
TPS
Coolant Sensor
O2 Sensor
Oil and filter change
trans fulid and filter change
Cylinder Head servised New HG, Bolts, etc.
New rotors and padsThere are 2 coolant sensors, IIRC one for the gage and a separate one for the fan and the PCM (which uses the data to control the mixture richness); which did you replace?
If the PCM is reading the engine as colder than it actually is, then it will try to make the ilde rich.
Once you press on the throttle pedal, the TPS and O2 sensor take over and PCM adjusts the FI based on O2-detected richness.

If the SES light is 'on' and there are stored codes, the PCM has put itself into a very rich, fail-safe limp-home operating mode called 'open loop.'
It won't go into 'closed loop' (where it adjusts fuel injection based on exhaust richness, as sensed by the front O2 sensor) until the offending codes clear.

You can temporarily erase the codes by disconnecting the battery for 10 minutes, but they'll come right back as soon as the PCM senses something wrong. Might take 2 seconds, might take 2 minutes or 2 hours, might take 2 days.
Then have the PCM scanned for free at AutoZone/Checker/CrappyTire and report back here with the code number.

bad fuel milage - Would it be: bad injectors, pressure regulator.
Often she will stall after i start her give her gas and sometimes she will not take the gas and shut off, start her again and she will be fineCould well be the Fuel Pressure Regulator, especially if the diaphragm is broken and leaking fuel directly into the intake manifold.
Try the 'suck test'.

[jftaylor]

Thanks alot But The suck test what is that oh yeah the coolent sensor that I replaced was FAN and PCM well here in Newfoundland gas $1.18 a liter put $30.00 worth in and got around 200 Kilometers thats realy bad

[rixGAphx]

The suck test, what is that?Do a 'search' for that term in the past day on this forum.gas $1.18 a liter put $30.00 worth in and got around 200 Kilometers that's realy bad$30 @$1.18 = ~25.4 liters = ~6.5 gallons.
200 kms = ~120 miles
120/6.5 = 18.4 miles/gallon.

A GA 4-cyl automatic should be getting about 25 city/hiway, so something's not right.

[Blackhawk]

What's the weather like where you are and are they still using the winter mix gas? Those two factors affect gas mileage too.

[shadowlurker]

Try putting in something like seafoam when you gas up. It helped me get like an extra 20-30 mile on a tank and im in a 3400

[rixGAphx]

jftaylor:

Is the SES light 'on'?
If so, what code(s) are being displayed?

Your best bet is to solve the problem(s) indicated by the code.
If it's for one of the newly-replaced sensors, then the problem might be with the wiring or connector, not the sensor itself.
Until then, the engine will always run very rich as the PCM 'default' mode.

The FPR or something else may also be wrong; and an FPR problem as such never causes a specific code.

[arthurgoboom]

x2 for FPR suck test...