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[TD="class: bgNone, width: 80%"]Runs rough | Erratic idle | - | negative adaptives | => Explanation of possible causes for a HIGH NEGATIVE ADAPTIVE CONDITION.;Prior to replacing parts, please review the explanation below in the recommendation field.[/TD]
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[TD="class: bgNone, width: 20%"]System or Component[/TD]
[TD="class: bgNone, width: 80%"]Engine Performance,Idle Concern,Rough / Unstable / Erratic Idle,Noise,Vibration,Odor Issues;Customer Concern (No DTCs);Group 18 - Vehicle Performance / Driveability[/TD]
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[TD="class: bgNone, width: 20%"]Recommendation[/TD]
[TD="class: bgNone, width: 80%"]Explanation of possible cause for a HIGH NEGATIVE ADAPTIVE CONDITION The adaptives become negative when the PCM decreases the injector pulse width in an attempt to make the oxygen sensor switch uniformly about the PCM's oxygen sensor goal voltage. This means that the oxygen sensor is producing a voltage that is close to one volt ( 1.0v ) consistently indicating a low oxygen (rich) state in the exhaust. The causes of the oxygen sensor reading a higher voltage usually falls into three main categories: 1) Excessive amount of fuel, 2) Not enough air, and 3) The PCM is being provided with the improper information. THE FOLLOWING IS A GENERIC LIST OF POSSIBLE CAUSES. THE LIST IS PROVIDED AS AN EXAMPLE OF POSSIBILITIES. SOME OF THESE MAY NOT APPLY TO YOUR SPECIFIC VEHICLE. IT IS YOUR RESPONSIBILITY TO DECIDE WHICH COULD APPLY. THIS IS NOT A COMPREHENSIVE LIST: MERELY THE MORE COMMON CAUSES. 1) EXCESSIVE AMOUNT OF FUEL -- there is such an abundance of fuel that there is no left over oxygen in the exhaust after combustion. -- This additional fuel could be caused by any of the following: TOO HIGH OF FUEL PRESSURE WRONG FUEL INJECTOR LEAKING OR WORN INJECTORS LEAKING INJECTOR O-RINGS CONTAMINATED CHARCOAL CANNISTER (liquid fuel) DEFECTIVE PURGE SYSTEM PRESSURE REGULATOR WITH A HOLE IN THE DIAPHRAM (vacuum compensated type ) CRANKCASE CONTAMINATED WITH FUEL (fuel contaminated with fuel other than gasoline such as diesel will wash past the piston rings and end up in the crankcase,) 2) NOT ENOUGH AIR- For some reason the cylinders are not filling with the proper amount of air. The amount of oxygen in the combustion chamber is low . This condition could be cause by any of the following: CAM TIMING-(including loose timing chain, sheared cam dowel pins, keyways, or skipped teeth) WORN CAM LOBES OTHER VALVETRAIN PROBLEMS RESTRICTED EXHAUST EXCESSIVE EGR FLOW FOR CONDITION- (Be sure to verify that the vacuum hoses to the EGR vacuum transducer are routed correctly. If the vacuum lines are reversed the EGR valve will open and stay open until the engine is shut off.) 3) PCM IS BEING PROVIDED IMPROPER INFORMATION- If the PCM does not receive proper sensor readings it will not deliver the proper injector pulse width for conditions. The following is a list of sensor problems that could cause short and long term adaptives to be highly negative: COOLANT SENSOR CALIBRATION (sensor is reading much colder than the actual engine temperature). OXYGEN SENSOR CIRCUIT PROBLEM- (this includes O2 sensor heater, grounds, signal wire problems, heater operation. Once the O2 sensor reaches operating temperature the voltage should never exceed 1.02v) MAP SENSOR CALIBRATION--One of the most important readings for testing a MAP sensor is the voltage reading obtained with the DRBIII with the ignition on and the engine off. This voltage reading is important because the PCM uses this for calculating barometric pressure. If the PCM does not "know" the correct air density from the MAP sensor (baro. reading) it will have to drastically change the fuel curve through the adaptives to get the proper response from the oxygen sensor. Below is a chart of key on MAP sensor readings for a given elevation. You should get to know what is normal for your area. Elevation (feet) Baro Reading (in.-hg.) MAP voltage 0 (sea level) 29.92 4.6v 29.67 500 29.42 29.17 1000 28.92 28.67 4.4v 1500 28.42 28.17 2000 27.92 27.67 2500 27.42 4.2v 27.17 3000 26.92 26.67 3500 26.42 26.17 4.0v 4000 25.92 25.67 4500 25.42 25.17 5000 24.92 3.8v VOLTAGE SENSE-- The PCM compensates the injector pulsewidth based upon charging system voltage. The higher the voltage => the stronger the magnetic field opening the pintle valve in the injector. The PCM compensates for this condition. If the PCM sense a lower voltage than is applied to the injectors the Adaptives will become negative.
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