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kfred 10/26/2013

2005 Honda Civic LX 4 Cyl 1.70L


What do I need to diagnose or check for when I have problems with engine efficiency and performance?

Haven't been getting as good of gas mileage or performance as I'm use to. Engine seems to lag as we.

1 Answer


Jimm 10/26/2013

First step - have the stored fault codes or check engine light scanned - for free - at any local auto parts store; Advance Auto, Auto Zone, NAPA. Then, post a reply as 'add answer' with the specific code for more assistance. There may be a fault code stored in the OBD memory which may not be displayed as a check engine light.

Here are a few engine problems that hurt fuel economy:
- 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 (inside dsitributor)
- defective oxygen sensor (causes rich mixture)
- defective coolant temperature 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)
- dirty mass air flow sensor (causes rich mixture)
- dirty air filter (causes rich mixture at high power)
- clogged or defective PCV valve
- incorrect valve clearance (especially if too tight)
- 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
- 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)
- increased exhaust back pressure caused by clogged catalytic converter, muffler or crushed pipe
- stuck exhaust manifold valve for some engines. Intended for fast warm up.

Other than these list of engine problems; there are other possibilities -
fuel system leaking, low tire pressure, wheels mis-aligned, brakes dragging / not fully retracted

There are similar possibilites for the hesitaion issue - as the two symptoms are often related;
Dirty fuel injectors (cleaning the injectors often fixes this)
Dirty air filter (change filter)
Dirty / clogged fuel filter (change filter)
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)

Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include:

Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires


kfred 10/26/2013

Add answer

There's no lights on though?


CVO 10/26/2013

The check engine light doesn't have to be ON to store a fault code.

Check the vehicle for fault codes to see if there are any sensors were involved to the malfunction of the engine.

1.Local auto parts stores such as Autozone ( not in California) or Advance Auto parts will scan and retrieve any diagnostic trouble codes ( dtc ) stored in the powertrain control module for free of charge..

2.See this http://www.amazon.com/.../ref=pd_sim_auto_4


kfred 10/26/2013

Okay I'll have then look tomorrow thanks

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