Air Flow Meter Gone?
Discussion
Hi Everyone. Was leafing through the 'Powertuning Rover V8's' book and it describes how to test the 5AM to make sure it's serviceable.
Carried out the tests today and looks like mine is on the way out:
The voltage on my DVM jumped to 0.9 V and then took about 4 seconds to come back down - just like the test says indicates failing.
Should I be paying any attention to this test? I don't want to spend a ton on a new AFM if these results aren't relevant to the TVR V8.
Mine's a '96 400 Serp by the way...
Cheers
Ryan
Carried out the tests today and looks like mine is on the way out:
The voltage on my DVM jumped to 0.9 V and then took about 4 seconds to come back down - just like the test says indicates failing.
Should I be paying any attention to this test? I don't want to spend a ton on a new AFM if these results aren't relevant to the TVR V8.
Mine's a '96 400 Serp by the way...
Cheers
Ryan
The time it takes for the voltage to drop, is the time it takes for the Hot wire and electronics to stablise. The response of the hot wire does alter if it gets caked in dirt, as it alters the thermal properties. You can see the dirt build up with a good eye glass, the thin grey wire will appear lumpy (its tiny). I would suggest you blip the throttle with the meter connected, and make sure the response is instant, and stays level when the revs are stable, and it does not lag behind the engine RPM or wander. Heres a picture of the hot wire, its inside the small hole as you look into the AFM.
This is Mark Adams take on the same subject:
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.
This is Mark Adams take on the same subject:
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.
t appears on the back end.HI
Prices etc were discussed on a recent thread
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Trev
Prices etc were discussed on a recent thread
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Trev
GreenV8S said:
FlipFlopGriff said:
We've killed a couple.
That sounds unusual. What are you doing that kills them?Two within the space of a few months. Latest ones has been on about 12 months now. Used daily but would expect longer life.
Got from a local chap off e-bay about £45 each.
Had one repaired but it lasted 5 minutes and then we were told that it was scrap so they refunded the refurb cost.
FFG
Blitz,
maybe you can help, Just fitted new AFM but idle is all over the place. Revs keep dropping out when clutching in on the slow down to a junction and when starting cold.
What voltage values should I have the CO idle set to - currently at 1.80 V as per factory spec.
Old one was 1.88 V
Would go back to old one but engine seems to be a bit more free to rev over 3000 and my rough running seems to have gone so think the new one is doing something right!
Ryan
maybe you can help, Just fitted new AFM but idle is all over the place. Revs keep dropping out when clutching in on the slow down to a junction and when starting cold.
What voltage values should I have the CO idle set to - currently at 1.80 V as per factory spec.
Old one was 1.88 V
Would go back to old one but engine seems to be a bit more free to rev over 3000 and my rough running seems to have gone so think the new one is doing something right!
Ryan
debaron said:
Blitz,
maybe you can help, Just fitted new AFM but idle is all over the place. Revs keep dropping out when clutching in on the slow down to a junction and when starting cold.
What voltage values should I have the CO idle set to - currently at 1.80 V as per factory spec.
Old one was 1.88 V
Would go back to old one but engine seems to be a bit more free to rev over 3000 and my rough running seems to have gone so think the new one is doing something right!
Sorry doesn't sound right to me.
I fitted one a few months back and idle was no problem the ecu adjusts itself to sort the AMM meter you don't need to adjust it.
You could try to reset the ecu no harm in trying.
Sounds more like a large air leak are your hoses on tight and do you have a good electrical connection there prone to failing.
Your idle was ok before you disconnected?
Ryan
maybe you can help, Just fitted new AFM but idle is all over the place. Revs keep dropping out when clutching in on the slow down to a junction and when starting cold.
What voltage values should I have the CO idle set to - currently at 1.80 V as per factory spec.
Old one was 1.88 V
Would go back to old one but engine seems to be a bit more free to rev over 3000 and my rough running seems to have gone so think the new one is doing something right!
Sorry doesn't sound right to me.
I fitted one a few months back and idle was no problem the ecu adjusts itself to sort the AMM meter you don't need to adjust it.
You could try to reset the ecu no harm in trying.
Sounds more like a large air leak are your hoses on tight and do you have a good electrical connection there prone to failing.
Your idle was ok before you disconnected?
Ryan
You must let the car idle for 20-30 seconds after fitting any new ECU part, to allow it to re adjust the long term fuel trim value. If you just get in and go, (especially after a ECU reset) it wont have time for the ECU to set things up with a stable RPM and throttle setting (hence its done at tickover). If this does not fix it, then get your test meter across the lambda probe connections- white and black. (It might be easier to get the connections where the extension cable is by the injector rails.) At tickover this should be switching between about .2 and .8 volts at about .5 second intervals. If its highly rich it will be constantly over .8v, or highly lean under .2v. An unstable idle could be either condition, and you can try altering the AFM setting to see if it can be changed.
mark
mark
Blitz, thanks for the advice:
Here's what I've done so far
Started up from cold this morning - gave it no throttle and let the ECU take control
revs unstable as follows:
spluttering at 400 revs for a few seconds then up to 1500 and slowly comes down to 1200 then splutters again and repeat. Added some manual throttle to stabilize as engine was shaking around and didn't like the noises it was making! After a minute or so of this, tickover smooth at 950.
Engine nice to drive and seems a lot more free and good power. Has alleviated my rough running - only thing of note is where I had a slight 'ticking' from the top left of the engine, it's now somewhat louder.
Will check Lambda's tonight. I've checked them before and relocated the lead to up near bonnet stay on Off Side and similar on Near Side so they are easier to get to!!
From memory, readings cycled between .8 and 1.4 V so may have been running very rich for ages!!
Adjusted CO idle reading from AFM to 1.9 V
Also - How do I safely reset the ECU!?!
Cheers
Ryan
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