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on my 1991 delta 88 oldsmobile ive lost half of my fuel economy over say the last 6 months its been slowly getting worse. Most of the time I owned it (3 years now) it got 11.76KM/L, right now its getting about 5.88KM/L my wife drives it hard and gets even less mileage I drive like a grandma nice and gentle on my car hehe. I was looking at this huge list to try and narrow it down.
ENGINE
- Compression: face your fears, it could be a bad engine
- Oil: maintenance item, part of basic tune up, dirty oil bad for fuel economy, can try lighter weight (0W-30) to minimally increase fuel economy (high mileage synthetic 5w-30, 3 months overdue for oil change)
- Throttle Position Sensor (TPS): influences fuel trim
- Knock Sensor: can retard timing if malfunctioning
- Coolant Temperature Sensor: influences fuel trim, on startup, cold engines need rich mixture, if malfunctioning you will always run rich, wasting fuel
- Thermostat: if stuck open, engine will remain too cool, failing to reach ideal operating temp; you can actually buy thermostats with a higher opening temp (stock is 170 for 5g, higher ones available at 180) to keep engine at higher temp, increasing efficiency (but possibly increasing wear to other components through increased heat exposure, eg, the cooling system)
ELECTRICAL
- Grounds: if corroded, weakened spark, incomplete burning, poor efficiency
- Ignition coil: if on its way out, won't ramp up voltage for spark plugs, get poor spark
- Ignition Timing: check it
- Distributor Cap and Rotor: wear item, part of basic tune up (points system)
- Distributor: check it (points system)
- Spark plugs: wear item, part of basic tune up (replaced within 15000km)
- Spark plug wires: wear item, part of basic tune up (replaced within 15000km)
AIR
- Filter: wear item, part of basic tube up, clean or replace it (replaced within 10000km, on a side note, new air filter causes engine to bog down in the rain.)
- MAP Sensor (Mass Airflow): influences fuel trim
- PCV valve
- EGR valve
- EGR intake ports
- Throttle body, IACV
- Catalytic Converter: check if blocked (not blocked)
- Primary Oxygen Sensor: influences fuel trim (replaced within 20000km)
FUEL
- Fuel Tank: can be dirty or contaminated
- Fuel Pump: on its way out equals low fuel pressure
- Fuel Filter (replaced within 20,000km)
- Fuel Pressure Regulator
- Fuel Injectors: dirty, clogged, stuck open
TIRES/BRAKES
- Tire Pressure: this is huge, just check them, you'll be surprised (keep my tires inflated at 40 psi)
- Alignment: check it (alignment is good but lower and upper ball joints need replacing)
- Brakes: check for drag (brakes newly installed within 20000km)
I would like your opinion as to where I should Start in this giant escapade of fuel economy I dont like to take my vehicles to mechanics and I think my car is in such shape they probably wouldnt let me leave the station with it either way hehe.
engine oil change is overdue by a few months and same for my tranny liquids.
this is my primary car atm but with its current condition will be my secondary car when I get my little blue festie on the road in a month or so (struts and tie rods and good to go!)
right now when driving it its fine for in town driving, but after about 45 mins of highway driving it starts to knock and misfire and surge, also has troubles keeping the cruise control on if we get to a hill or a gust of wind it will kick off cruise control. has a hard time going up hills lately.
thank you in advance
ENGINE
- Compression: face your fears, it could be a bad engine
- Oil: maintenance item, part of basic tune up, dirty oil bad for fuel economy, can try lighter weight (0W-30) to minimally increase fuel economy (high mileage synthetic 5w-30, 3 months overdue for oil change)
- Throttle Position Sensor (TPS): influences fuel trim
- Knock Sensor: can retard timing if malfunctioning
- Coolant Temperature Sensor: influences fuel trim, on startup, cold engines need rich mixture, if malfunctioning you will always run rich, wasting fuel
- Thermostat: if stuck open, engine will remain too cool, failing to reach ideal operating temp; you can actually buy thermostats with a higher opening temp (stock is 170 for 5g, higher ones available at 180) to keep engine at higher temp, increasing efficiency (but possibly increasing wear to other components through increased heat exposure, eg, the cooling system)
ELECTRICAL
- Grounds: if corroded, weakened spark, incomplete burning, poor efficiency
- Ignition coil: if on its way out, won't ramp up voltage for spark plugs, get poor spark
- Ignition Timing: check it
- Distributor Cap and Rotor: wear item, part of basic tune up (points system)
- Distributor: check it (points system)
- Spark plugs: wear item, part of basic tune up (replaced within 15000km)
- Spark plug wires: wear item, part of basic tune up (replaced within 15000km)
AIR
- Filter: wear item, part of basic tube up, clean or replace it (replaced within 10000km, on a side note, new air filter causes engine to bog down in the rain.)
- MAP Sensor (Mass Airflow): influences fuel trim
- PCV valve
- EGR valve
- EGR intake ports
- Throttle body, IACV
- Catalytic Converter: check if blocked (not blocked)
- Primary Oxygen Sensor: influences fuel trim (replaced within 20000km)
FUEL
- Fuel Tank: can be dirty or contaminated
- Fuel Pump: on its way out equals low fuel pressure
- Fuel Filter (replaced within 20,000km)
- Fuel Pressure Regulator
- Fuel Injectors: dirty, clogged, stuck open
TIRES/BRAKES
- Tire Pressure: this is huge, just check them, you'll be surprised (keep my tires inflated at 40 psi)
- Alignment: check it (alignment is good but lower and upper ball joints need replacing)
- Brakes: check for drag (brakes newly installed within 20000km)
I would like your opinion as to where I should Start in this giant escapade of fuel economy I dont like to take my vehicles to mechanics and I think my car is in such shape they probably wouldnt let me leave the station with it either way hehe.
engine oil change is overdue by a few months and same for my tranny liquids.
this is my primary car atm but with its current condition will be my secondary car when I get my little blue festie on the road in a month or so (struts and tie rods and good to go!)
right now when driving it its fine for in town driving, but after about 45 mins of highway driving it starts to knock and misfire and surge, also has troubles keeping the cruise control on if we get to a hill or a gust of wind it will kick off cruise control. has a hard time going up hills lately.
thank you in advance
)
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