12.44 - Code 44 ( ,
The code 44 and 26 have some overlap. Code 44 means that the oxygen sensor is signaling the computer that the fuel mixture is bad - too rich or too lean. The car can then not run in closed loop mode, and the VCM after a while ignores the oxygen sensor and goes to a default mode. If the sensor itself was bad, the car would probably run just fine, but use more gas, although in some cases will run irregularly. More likely you have a true, too lean or too rich problem.
The first step in diagnosis is to idle the car until the car runs rough or the error light is activated. Then, using a DIGITAL multimeter, measure the output of the oxygen sensor by back probing it while still connected - do this at the junction of the wire from the sensor on the right (US) fender well. It will oscillate rapidly under normal conditions from .9 to 2v. If mixture is too lean it will read very low all the time. Check with a manual for the actual voltages, these may be incorrect, or vary between models.
TOO LEAN: If you determine that the mixture is too lean, then you have either fuel starvation or an intake air leak. If the car idles OK but has loss of power at speed, then you likely have fuel starvation. An intake air leak will cause bad idle but will be less noticeable at speed.
TOO RICH OR AMBIGUOUS: This could be a sensor problem (air mass sensor, throttle pot or others), but most likely an ignition problem. This may well be the most common cause for code 44. Before you do anything you check the ignition, try just replacing distributor cap and rotor , spark plug wires, and spark plugs. - Its cheap and easy and maintenance anyway. It might be possible that a misfire resulted in fouling of the oxygen sensor (code 26), then when replaced with a new one you got code 44.
Conditions for flagging...
- Engine coolant temp above 167F,
- Throttle position under 3 volts,
- 450 engine revolutions in a row no oxy sensor switching.
- Fuel pressure fault,
- Stuck open purge valve,
- Poor ground connections,
- Poor oxy sensor ground connection,
- Open or short in oxy sensor heater and/or output circuit,
- Defective air injection pump or circuit,
- Intake air leak,
- Plugged fuel injector (or bad electrical connection)
- Defective maf sensor.
Do a hot engine vacuum reading. At about sea level, you should get roughly 20 inches of vacuum at hot idle.
You can have a vacuum leak in many impossible to see places....
- The egr system/pipes/valve,
- The vapor recovery system...at the vacuum port under the throttle (nipple falls out of manifold), at the charcoal canister hoses in the front air dam, intake manifold,
- Crankcase vent system, etc.
After that, check the fuel pressure and the injectors. You can unbolt the rail from the intake manifold and remove it, then remove each injector and check the intake screens. At that time, you can also remove the fuel pressure regulator and using air pressure, test the pressure set point. Should be 44 psi without any vacuum on the vacuum port. Fuel pressure typically runs between 32 to 44 psi, 44 psi full throttle (no vacuum), 32 psi with 20 inches of vacuum...
Ignition problems typically set a ff26. During a severe miss, fuel and air is dumped into the exhaust, setting the FF26. For FF44, the engine seems to not be able to get enough gas into the mixture. This means a shortage of fuel, or an abundance of air.
When heated with a torch till its hot and slightly glowing, the oxy sensor should put out about .9 volts. Voltage reading will vary around as you move the torch, but if it gets up to .9 volts, its ok.
I doubt they fail often, typically when the heater gets erratic. They have to be hot to work, so if they don't get hot, they don't work. The relay that powers the heater also runs the fuel pump.
You could have a big vacuum leak when the ecu operates the canister purge. The ecu will open the solenoid to purge the fuel vapors in the canister after the engine is up to at least 93F and above idle.