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Buick regal 92 limited 3.8L 104000KM ,Major poor fuel economy, NO engine lights, light gas scent sometimes . What parts can cause such horrible fuel mileage???! Please help currently get 10 MPG , already changed spark plugs, ignition wires , fuel filter , air filter, regular oil changes, car starts everytime, fuel pump sound like its working
Sounds like you might have an oxygen sensor problem. Your catalytic converter(s) maybe defective or dirty. That in turn can dirty up the oxygen sensor. A defective oxygen sensor will send faulty info to the computer, interpreting the fumes as cold (even when the engine warms up). That causes the computer to adjust the fuel mixture to very rich, giving you poor gas mileage and the fuel smell. Hope it helps.
The Oxygen sensor is a good possibility but should be showing a trouble code, but the gas smell bothers me. Unless you are at the back end at the exhaust pipe, you should not smell gas. This usually means a leak which sure can affect mileage. Jack the car up and support it safely. Crank the car up and look for wet spots and or drips. The ECM on the car can be bad which would explain poor mileage and no trouble codes. I've had many 3.8 engines and always got 30 mpg or better on trips.
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Okay- thanks for the public announcement;...just kidding!
Mike it sounds like you have a heavy foot on the gas pedal- speeding around town- Ohhh, I gotcha' again! Or someone is pilfering your gas by siphoning it out; LOL
Okay, all kidding aside, the following issues can cause poor fuel economy:
Incorrect tire pressure
a bad or malfunctioning oxygen sensor
dirty or plugged air filter
dirty or malfunctioning fuel injectors
improperly working spark plug(s) e,g. misfires or improper gap
poor driving habits, like sudden accelerations
engine idling for inordinate or extensive amounts of time
and as silly or unbelievable as it might sound, the type of motor oil...the viscosity that is used can affect gas mileage by up to 10-12%; regular oil changes using synthetic or manufacturer recommended oil that reduces friction should be employed.
Defective coolant sensor
Defective thermostat
a leak in the intake manifold or EGR
Poor compression- If you are driving a car that has high mileage, over 100,000 miles, affects fuel economy
clogged catalytic converter or some other restriction in the exhaust system
Dragging brakes
slipping clutch or transmission
Lugging around excess weight in the car
Any single one of...or combination of the above, could greatly reduce engine performance and affect gas mileage.
First and most important, check the fuel rail,injectors and fuel lines to the engine and make sure you have no leaks. If you can't see the injectors on the back side, get a mirror and good light. This needs checked. Next check the fuel pressure regulator. pull the vacuum hose off of it and smell for gas in/at the hose. If you smell gas, replace the regulator. Next check all the vacuum lines broken ones cause a lean mixture and the computer will throw more gas to the engine. You must have the check engine light on, Check for codes. If it isn't check for codes anyway.
P0139 - Oxygen Sensor Circuit Slow Response (Bank1, Sensor2)
- Faulty Rear Heated Oxygen Sensor Bank 1
- Rear Heated Oxygen Sensor Bank 1 harness is open or shorted
- Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection
- Inappropriate fuel pressure
- Faulty fuel injectors
- Intake air leaks may be faulty
- Exhaust gas leaks
Best advice check it out first!
DO NOT Shotgun it as in replace things until it works. You are blowing money at that point.
Good gas mileage on this car should be 19City 27Hwy. Gas mileage can be affected by many things. Assuming that the car has been recently tuned as you have indicated, I would:
Check tire pressure first<-you'd be surprised what low tire pressure can do.
Check for low oil level <-engine friction
Cheap spark plugs.
Let me know.
Try having your fuel injector cleaned, you can start with running fuel injector cleaner though your gas tank and if that does not help then you have to get it cleaned out professionally or even worst have the injector's replaced if they are bad.
The other thing that will give it bad fuel would be a bad air intake temperature sensor go bad, as for the ruff idle that is common to a dirty or stuck EGR valve.
Good luck and keep me posted, by the way, what kind of Garage did you take it too? And are there and DTC codes from the ECM?
You will see shorter service life of those O2 sensors with that kind of mileage. I would also suspect that the injectors are seriously worn if original. a few things to also look at that tend to throw 02 codes:
1: MAP OR MAS sensors,
2. worn timing chain
3: Restricted air intake (filter, or leak between MAS sensor and Intake)
4: Engine coolant thermostat (if the engine never warms fully, the mixture will be overly rich)
The O2 sensors tend to get wiped out by too much or too little fuel, too much in your case. you have to find the problem of fuel delivery or it will kill any O2 sensors you replace.
Have you performed a compression check? in some cases the piston, or rings have failed and allowed a large amount of fuel to enter the crankcase oil.
Sounds like you've got a defective fuel level sending unit. It's in your tank, probably attached to the boost pump assembly. Normally the top of the tank can be accessed via the trunk where you should be able to remove the assembly for replacement. While you're in there, look around in the tank with a very bright flashlight for any debris or pieces from the assembly laying on the bottom.
Horrible gas mileage can be caused by very many things. Try to buy an OBDII diagnostic scanner to figure out what's malfunctioning. Sensors don't last very long, and can wreak havoc on performance and economy.
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