Discussion
Have just replaced my AFM to stop over fueling and odd running at low revs.
do i need to reset anything now or is it meant to do that automatically ?
i ask this because it now seems to be running very uneven at low speeds, almost cutting out then reving to 1000rpm then down etc..
is there a reset someplace or is it not that simple.
before anyone says anything im not even slightly mechanically minded..thanks in advance
do i need to reset anything now or is it meant to do that automatically ?
i ask this because it now seems to be running very uneven at low speeds, almost cutting out then reving to 1000rpm then down etc..
is there a reset someplace or is it not that simple.
before anyone says anything im not even slightly mechanically minded..thanks in advance
wargriff said:
well I have disconnected the ECU, but i still have the surging at low revs..when cold engine is stalling. Is there another obvious thing im missing, or is it beyond my skill level now and I need a garage ?
Worth checking the connector onto the coolant temperature sensor just to make sure there is no corrosion giving a false resistance (the sensors themselves don't last for ever either). You'll find that facing upright behind the distributor ish, in the inlet manifold (taps into a water gallery); will have a 2 pin mini-timer plug on it (squareish plastic affair with a steel clip)If no joy there, just try driving it for a few miles and getting it up to temperature, give the ECU chance to apply some trims.
Just wondered if you know the history of the replacement AFM? It is possible that it could be duff too. If you know it is a good one then it may be just a simple matter of adjusting the CO trimmer.
Here's a quick fault finding guide.
Note that you can drive without an airflow meter in case of emergency (i.e. airflow meter disconnected), because the system will drop into a default (limp-home) mode based on throttle opening.
Most airflow meter faults will cause the engine to run excessively rich. However if the airflow meter remains connected whilst defective then the vehicle will probably not run. In most cases the output from a defective airflow meter will be in the range 2.0-2.5 Volts, which is a viable value. This represents a moderate load and will cause heavy over-fuelling without setting a fault code.
Testing is performed in the following manner. Peel back the rubber boot on the airflow meter connector and leave it plugged in to the airflow meter. Set up the digital multimeter to read voltage. Insert the negative probe into the Red/Black wire (sensor ground), and the positive into the Blue/Green wire (Airflow signal).
Turn on the ignition, but do not start the engine. The meter should immediately indicate a reading of approximately 0.3-0.34 Volts. Most defective airflow meters will overshoot to 0.8 Volts or higher, and take at least 2 seconds to come down to the correct voltage.
Now start the engine, and the reading should rise to 1.6 Volts (3.5 Litre engine) to 1.75 Volts (5.0 Litre engine).
The next test is full load, and as with the fuel pressure test it will require use of a rolling road or a steep hill in the same manner. Under full load the voltage should rise to 4.45 Volts (3.5 Litre engine) to 4.95 Volts (5.0 Litre engine).
On this injection system, the idle CO mixture adjuster is provided on the airflow meter. It is located in a boss on the top of the airflow meter, pointing towards the engine. Leaving the multimeter negative probe in the Red/Black wire, move the positive probe to the Blue/Red wire.
Now turn on the ignition but do not start the engine. Observe the voltage. The normal adjustment range is between 0.0 and 3.6 Volts, with the higher Voltages producing higher idle CO values. There are approximately 20 turns of the adjuster screw to cover the entire range.
Annoyingly, the adjustment may be clockwise or anticlockwise to increase the value, and this varies from meter to meter! For this reason it is always preferable to have the multimeter connected in this manner when adjusting idle CO, so that you see can something is actually happening.
Typical Voltages that would be found at this point are between 0.9 to 1.4 Volts for non-catalyst cars. This Voltage is always factory pre-set to 1.8 Volts for catalyst vehicles. A value near to 3.5 Volts will generally produce an idle CO value of 9-10%. These Voltages may be used as safe initial values particularly if no CO measuring equipment is available.
If you want any more info then PM me. Good Luck!
Here's a quick fault finding guide.
Note that you can drive without an airflow meter in case of emergency (i.e. airflow meter disconnected), because the system will drop into a default (limp-home) mode based on throttle opening.
Most airflow meter faults will cause the engine to run excessively rich. However if the airflow meter remains connected whilst defective then the vehicle will probably not run. In most cases the output from a defective airflow meter will be in the range 2.0-2.5 Volts, which is a viable value. This represents a moderate load and will cause heavy over-fuelling without setting a fault code.
Testing is performed in the following manner. Peel back the rubber boot on the airflow meter connector and leave it plugged in to the airflow meter. Set up the digital multimeter to read voltage. Insert the negative probe into the Red/Black wire (sensor ground), and the positive into the Blue/Green wire (Airflow signal).
Turn on the ignition, but do not start the engine. The meter should immediately indicate a reading of approximately 0.3-0.34 Volts. Most defective airflow meters will overshoot to 0.8 Volts or higher, and take at least 2 seconds to come down to the correct voltage.
Now start the engine, and the reading should rise to 1.6 Volts (3.5 Litre engine) to 1.75 Volts (5.0 Litre engine).
The next test is full load, and as with the fuel pressure test it will require use of a rolling road or a steep hill in the same manner. Under full load the voltage should rise to 4.45 Volts (3.5 Litre engine) to 4.95 Volts (5.0 Litre engine).
On this injection system, the idle CO mixture adjuster is provided on the airflow meter. It is located in a boss on the top of the airflow meter, pointing towards the engine. Leaving the multimeter negative probe in the Red/Black wire, move the positive probe to the Blue/Red wire.
Now turn on the ignition but do not start the engine. Observe the voltage. The normal adjustment range is between 0.0 and 3.6 Volts, with the higher Voltages producing higher idle CO values. There are approximately 20 turns of the adjuster screw to cover the entire range.
Annoyingly, the adjustment may be clockwise or anticlockwise to increase the value, and this varies from meter to meter! For this reason it is always preferable to have the multimeter connected in this manner when adjusting idle CO, so that you see can something is actually happening.
Typical Voltages that would be found at this point are between 0.9 to 1.4 Volts for non-catalyst cars. This Voltage is always factory pre-set to 1.8 Volts for catalyst vehicles. A value near to 3.5 Volts will generally produce an idle CO value of 9-10%. These Voltages may be used as safe initial values particularly if no CO measuring equipment is available.
If you want any more info then PM me. Good Luck!
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