when at about 2400 rpm my car jerks a little im getting a code 45 which is"system adaptive fuel too rich/lean" what should i check first??

 

Replace your 02 sensor.

If you keep your eye on fuel gauge, you will notice that your are gettingth worst fuel mileage possible.

Also make sure your gasp is secure. Always, turn the gas cap three clicks.

 

For real, call me crazy but keeping track of your gas mileage is the best way to find if something is wrong...before it gets bad enough to flip a code.

 

whould'nt a specific code pop if it was the o2 sensor>

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by zollirum &raquo;</TD></TR><TR><TD CLASS="quote">whould'nt a specific code pop if it was the o2 sensor&gt;</TD></TR></TABLE>

Not initially, only if it gets really bad and the ECU knows it to be obviously wrong. O2 sensors create voltage (don't ask me to explain how), but we're talking really low voltage and amps so its a low spectrum to begin with. As it goes bad that spectrum changes but it never cuts out all together, hence you get an innacurate reading but the ECU still reads the sensor and no code.

You can check it with a voltmeter by the way. That's how I confirmed it was bad on my old eclipse.

 

Don't really mean you have an 02 sensor problem.

When the car starts (cold), you should see approximately .450 Volt (450mv) on the O2 output wire. This reading often varies slightly. The system is now in open loop.

After a few minutes (less if the engine is warm or the O2 Sensor is heated), this reading should begin to fluctuate. You will see changing numbers ranging from near 0 volt to near 1 Volt. If these readings occur, everything is ok. The O2 sensor's output should vary relatively quickly. A lazy sensor, would show up here and the readings will vary slowly. If the readings don't start to vary (stay in open loop), you now are aware of it and can begin to look for the reason.

Remember, a lean reading is under 350 mv, a rich condition is over 600 mv.

Now here are some things to look at:

For lean O2 sensor readings:

1. Check sensor output wire for possible grounding. A ground will cause a false lean signal.

2. Check the MAP sensor for proper vacuum to voltage output. A high vacuum signal will cause a lean ecu reaction.

3. Clogged injectors can cause a false lean condition. A cleaning may solve the problem.

4. Water contamination will cause a lean condition.

5. Low fuel pressure will cause lean conditions at any rpm or load range. Be sure to check pressure at all driving modes.

6. Exhaust leaks, especially near the sensor can pull in air and cause a false lean reading.

7. Check for proper air injection system operation. The air pump should not direct air to the exhaust ports during closed loop operation.

For rich O2 sensor readings:

1. Check the fuel pressure. High readings will cause rich conditions.

2. Leaking injector(s) will cause rich exhaust.

A leak down test and/or a power balance test can usually reveal the leaker.

3. A contaminated or malfunctioning canister purge system can very easily put uncontrollable amounts of fuel into the intake manifold. Simply disconnecting the vapor hose can reveal this as your problem system.

4. Check vacuum to voltage readings at the MAP sensor. A low MAP output will cause a rich ecu reaction. (Don't forget vacuum readings again!)

5. A false tps signal can cause the system to go rich if the Ecu sees a high tps output. Check tps readings at idle and for a smooth rise to wide open throttle.

fs