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Getting poor fuel economy? Check this comprehensive troubleshooting guide.
Yes, there have been many threads on this--but all basically repeat the same old mantra of "do your basic maintenance/tune up." In trying to research my own low power/fuel economy, I came across many more subtle causes which I've never seen mentioned here before, but which can have significant impact.
So if you have poor performance and fuel economy, have done your basic maintenance and are still stumped, then check the following list. For the sake of completeness, it includes both common causes and zebras.
By no means am I an expert in any of this, so if anything's wrong or missing, please feel free to comment, and I'll update the list.
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
- 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
- Distributor: check it
- Spark plugs: wear item, part of basic tune up
- Spark plug wires: wear item, part of basic tune up
AIR
- Filter: wear item, part of basic tube up, clean or replace it
- MAP Sensor (Mass Airflow): influences fuel trim
- PCV valve
- EGR valve
- EGR intake ports
- Throttle body, IACV
- Catalytic Converter: check if blocked
- Primary Oxygen Sensor: influences fuel trim
FUEL
- Fuel Tank: can be dirty or contaminated
- Fuel Pump: on its way out equals low fuel pressure
- Fuel Filter
- Fuel Pressure Regulator
- Fuel Injectors: dirty, clogged, stuck open
TIRES/BRAKES
- Tire Pressure: this is huge, just check them, you'll be surprised
- Alignment: check it
- Brakes: check for drag
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Last edited by devtec; 04-27-2009 at 11:47 AM.
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