Discussion
Hi guys n girls
Within the first 1,000 miles of owning my Griff 500 my AFM gave up. I replaced it with a recon unit from Bell Hill.
10,000 miles later (2 years) this one gave up. I could unplug it and there was no change. Again I replaced it with a recon unit.
Now only 80 miles (2 weeks) later it's happened again.
My question is, have I just been unlucky or do you think something else is causing the AFM to break?
When it's working I can pull the plug and the car die's. Each time it's gone faulty unplugging makes no difference at all!
Within the first 1,000 miles of owning my Griff 500 my AFM gave up. I replaced it with a recon unit from Bell Hill.
10,000 miles later (2 years) this one gave up. I could unplug it and there was no change. Again I replaced it with a recon unit.
Now only 80 miles (2 weeks) later it's happened again.
My question is, have I just been unlucky or do you think something else is causing the AFM to break?
When it's working I can pull the plug and the car die's. Each time it's gone faulty unplugging makes no difference at all!
They are simple creatures these AFMS. You only have earth, 12 volts, afm output, and the trim resistor. I cant see how anything external could cause them to fail prematurely, unless the AFM output is shorted to ground termittently. This could blow up the internal electronics, but wont harm the ECU. Dirt (and oil) on the hot wire can also mess things up. Do a simple test, remove the AFM from the tubing, put a DC test meter between the red and black wire, and the blue green in the plug. Tthe connectors are deep in the plug- you may need a couple of sewing pins to get down the side of the wires. Power on the ignition and the voltage should settle at less than a volt withing a second or so. Then simply blow into the hotwire port (Small hole in the side of the AFM if you look into the air intake side) and the voltage will shoot up if its working. It will be quite obvious as the units are very sensitive to low airflow changes.
Heres Mark Adams take on the same subject:
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.
Heres Mark Adams take on the same subject:
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.
Another update: -
After taking readings from all areas that go to the AFM and anything on common wiring it now works.
Therefore, I think it is a broken wire somewhere or a connection wasn't made correctly. I don't know where as I did a lot of pulling and pushing of wires and connectors
Now I'm thinking the AFM that was replaced 2 weeks ago may not have been faulty after all!
Live and learn
After taking readings from all areas that go to the AFM and anything on common wiring it now works.
Therefore, I think it is a broken wire somewhere or a connection wasn't made correctly. I don't know where as I did a lot of pulling and pushing of wires and connectors
Now I'm thinking the AFM that was replaced 2 weeks ago may not have been faulty after all!
Live and learn
davetherave1970 said:
Therefore, I think it is a broken wire somewhere or a connection wasn't made correctly. I don't know where as I did a lot of pulling and pushing of wires and connectors
Vehicle wiring products
6 Pole female housing: 192173
Terminals: 192175
Seals : 192177
Or 4 of these
ETA: Big thanks to HRG for the suppliers addy & wrong part numbers he gave me
Edited by Seasider on Tuesday 21st April 23:21
zippy500 said:
Nice. I need to replace mine as it's got a broken moulding and No rubber cover any longer.
Can 192154 be used as the large sleeve to keep it all neat?
And I'm guessing you need 4 little seals?
I have 10 seals & spades + 2 boots sitting in front of me Can 192154 be used as the large sleeve to keep it all neat?
And I'm guessing you need 4 little seals?
ready for when i get round to replacing the temporary option B thats on my car atm 
The extra bits, for if i lost broke or f
ked up when i make the plug up 
The boots not a really tight fit as its for the 7 pin plug but it might pull down onto the lower part of the plug, if not, i reckon a small cable tie
Gassing Station | Griffith | Top of Page | What's New | My Stuff