General maintenance
Introduction
OK, so technically this isn't a mod.
But it must be said that the starting point for an efficient vehicle is one that's maintained in good condition. There's little point in building on a weak foundation.
Particularly if you're driving an older vehicle, there are a number of maintenance items that should be checked to ensure you're starting from the best possible position.
Contents
Instructions for mod
Check for any of the following
- missing or defective thermostat, causing low operating temperature
- clogged intake manifold exhaust crossover passage (for heating intake manifold)
- engine misfire caused by bad spark plug, ignition wire, coil, dist. cap or rotor
- late ignition timing
- bad vacuum advance unit (common in old cars)
- stuck centrifugal advance mechanism in distributor (needs oil occasionally)
- bad tension adjustment of centrifugal advance springs
- defective oxygen sensor (causes rich mixture)
- defective coolant temp. sensor for engine computer (causes rich mixture)
- worn timing belt (may cause rich fuel mixture in fuel injected cars with a MAP sensor)
- incorrect timing belt installation (timing marks should line up)
- sticking or poorly adjusted carburetor choke (causes rich mixture)
- dirty air filter on an engine with a carburetor (causes rich mixture at high power)
- clogged or defective PCV valve
- incorrect valve clearance (especially if too tight)
- high performance camshaft installed (not efficient at low power)
- worn valve guides (makes fuel mixture too lean at low power)
- vacuum leak from bad vacuum hoses or intake system gaskets (causes lean mixture)
- dirty fuel injectors
- bad fuel pressure regulator
- bad MAP sensor for fuel injection
- leaking intake duct between air flow sensor and throttle body
- too much alcohol in gasoline with old car (requires carb. modification for correct mixture)
- rusted or missing exhaust heat stove or pipe for heated air intake
- loss of compression pressure due to worn rings or leaking valves
- sticking EGR valve (causes rough idling and rich mixture on some engines)
- exhaust backpressure caused by clogged catalytic converter, muffler or crushed pipe
- stuck exhaust manifold valve for some V type engines. Intended for fast warm up.
More engine problems:
- high idle speed
- high fast idle speed when cold
- incorrect idle mixture adjustment (carburetor or fuel injection)
- leaking fuel line or carburetor (dangerous too)
- clogged jets (calibrated holes) inside carburetor
- defective power valve in carburetor
- worn camshaft lobes
- high alternator voltage (should be about 14 volts when warm)
- high oil level (interferes with crankshaft movement)
- high oil pressure (relief valve stuck or has wrong spring)
- stuck cooling fan clutch (runs fan when not needed)
Problems that increase rolling resistance:
- sticking disk brake calipers
- tight drum brake adjustment
- warped brake rotor or drum
- sticking parking brake cable
- incorrect wheel alignment, front or rear (check tire wear)
- worn suspension joints (ball joints, steering joints)
- worn control arm bushings (changes wheel alignment)
- worn or incorrectly adjusted wheel bearings
- leaking grease seals for wheel bearings
- use of snow tires when not needed
- leaking tires, causing loss of pressure
- warped tires
- bent rims, causing car to shake
- poor wheel balance, causing shaking at high speeds
- worn shocks or springs (forces driver to brake more)
Automatic transmission problems:
- wrong fluid level
- incorrect throttle valve cable adjustment
- bad vacuum modulator or vacuum hose to modulator
- sticking valves in valve body, causing delayed shifts; changing transmission fluid may help
- failure of torque converter to lock up (if equipped with lock-up torque converter); it should engage at 30-55 MPH, reducing engine speed about 10%
- stuck stator clutch in torque converter
Manual transmission problems:
- wrong fluid level
- excessive oil viscosity
- bad bearings
- failure to engage one or more gears
Differential problems:
- wrong fluid level
- excessive oil viscosity
- bad bearings
- high ratio ring and pinion gear set installed for racing
User experiences
Please enter your user name and any relevant data in the table
| User Name | Car Make, Model, Year | Cost of Mod | Time to Perform Mod | MPG Before Mod | MPG After Mod | MPG improvement guess | Instruction Link |
|---|---|---|---|---|---|---|---|
| Example Data Saand | Example Data Mazda, 626, 1991 | Example Data $5 USD | Example Data 1 Hour | Example Data 27.2 | Example Data 29.8 | User mod detail or measurement detailed data |
Problems / Consequences of mod
Information required: What are the consequences of the mod, Eg: drivability issue, stalling, engine wear,
References
Forum thread links
List of common mechanical problems that hurt fuel economy
