Incorrect Lambda reading - Rovergauge - AFM
Discussion
Hi All,
I hope the Chim-crowd reads here as well since they have the same engines.
I have a serp 500Griff from 1997 with CAT.
I recently found out with rovergauge, that my lambdas reading apparently rich and the 14CUX tried to correct that.
The long term fuel trim in rovergauge was all the way down to -100% both banks.
But the Lambdas were still working, since the short term values were still going up and down.
So I hooked the oscilloscope to the lambdas and really - the read lean (cycling rich-lean, but stayed on the lean side most of the time).
I read on here, that the reason may be a shot AFM. There is also a test described somewhere, that the sensing voltage of the AFM has to drop to 0.3V immediately after startup - mine didn't and took some seconds to end up at 0.5V. So I bought one off Rimmerbros called ERR 5198 and swapped it.
Now my long term trim values go all the way to +100% - wtf(?)! And it really runs rich at Idle and has misfires (which surely don't help).
1st Question: Is there an explanation, why a faulty AFM should make the Lambdas read wrong (or be misunderstood by the 14CUX)?
2nd Question: May the ERR-5198 be wrong? (It is not RR since there are only aftermarket versions available)
Anyone has experienced that?
The only thing I changed is the Rover distributor that I swapped to the 123Tune - could that be it?
I hope somebody can help!
Rgds,
Marvin
I hope the Chim-crowd reads here as well since they have the same engines.
I have a serp 500Griff from 1997 with CAT.
I recently found out with rovergauge, that my lambdas reading apparently rich and the 14CUX tried to correct that.
The long term fuel trim in rovergauge was all the way down to -100% both banks.
But the Lambdas were still working, since the short term values were still going up and down.
So I hooked the oscilloscope to the lambdas and really - the read lean (cycling rich-lean, but stayed on the lean side most of the time).
I read on here, that the reason may be a shot AFM. There is also a test described somewhere, that the sensing voltage of the AFM has to drop to 0.3V immediately after startup - mine didn't and took some seconds to end up at 0.5V. So I bought one off Rimmerbros called ERR 5198 and swapped it.
Now my long term trim values go all the way to +100% - wtf(?)! And it really runs rich at Idle and has misfires (which surely don't help).
1st Question: Is there an explanation, why a faulty AFM should make the Lambdas read wrong (or be misunderstood by the 14CUX)?
2nd Question: May the ERR-5198 be wrong? (It is not RR since there are only aftermarket versions available)
Anyone has experienced that?
The only thing I changed is the Rover distributor that I swapped to the 123Tune - could that be it?
I hope somebody can help!
Rgds,
Marvin
PH430 said:
Ask Mark Tompson of g33.co.uk
Use search on here to find him - blitzracing is his PH name. Then email him via PH. He's a good guy and will respond. He knows everything about Rovergauge and is always happy to help. I vaguely remember my long term trim is -100%, and that he said that was ok. If I can find time later I will hook my laptop up to the car and see what RG says on mine, which is running fine.
I do have a spare 5AM that i can post out to you to try if you want to try another, but it came in a job lot of spares I bought, so i will need to test it first, so that might take a few days.
Thanks a lot guys!
I did contact Mark, lets see if he can come up with something.
Is it possible, that a new AFM may have its CO-trim value not adjusted and I have to do that?
I read two instructions:
1) With the AFM connected, make sure between the red/black cable and the red/blue cable are 1.8V (CAT car) - adjust the trim with the adjusting screw on the outside.
2) With the AFM disconnected, make sure the resistance between the outer two pins is 300Ohm. Again - adjusted by outside screw.
Anyone done that before?
Shouldn't the AFMs come with 1.8V out of the box?
I have currently no time to go to the garage and I will check that later.
Have fun!
Marvin
I did contact Mark, lets see if he can come up with something.
Is it possible, that a new AFM may have its CO-trim value not adjusted and I have to do that?
I read two instructions:
1) With the AFM connected, make sure between the red/black cable and the red/blue cable are 1.8V (CAT car) - adjust the trim with the adjusting screw on the outside.
2) With the AFM disconnected, make sure the resistance between the outer two pins is 300Ohm. Again - adjusted by outside screw.
Anyone done that before?
Shouldn't the AFMs come with 1.8V out of the box?
I have currently no time to go to the garage and I will check that later.
Have fun!
Marvin
The AFM idle Voltage is critical to get the long term trim correct, as the ECU only sets the long term trim at Idle. It takes only 150mv error to throw the fuelling out. So as you have RoverGauge check the percentage reading in direct mode at idle- it should fall between 32 and 35 percent- as yours is the bigger engine, it should be very close to 35%. Im disappointed that Rimmer have sold you an aftermarket part- Ive yet to find a Chinese replica that actually works reliably! I did not think the supply of genuine Lucas parts had quite dried up yet- but they are just expensive. Any type of 5AM will work- there is a whole host of Lucas part numbers, that cover various castings (that bolt off the main body) but the electrical output is the same. There is a Jag 5am as well, but its missing the trim resistor, so Id avoid it. There should be plenty floating around on scrap Range Rovers, and these don't get the cooking that they do on the TVR.
Hi Mark,
Thanks a lot for your reply.
If I understand that correctly I have a Chinese copy and no genuine Lucas part. That is why the measured value is slightly off and therefore the 14CUX gets confused and messes with the long term trim.
Now can I do anything with the CO adjustment or will that not help?
Could I do anything in the cable, like adding a resistor?
Rimmer Bros advertised this AFM as "aftermarket" so at least they were not lying. Where do I get a real one and how do I recognize it?
Have fun!
Marvin
Thanks a lot for your reply.
If I understand that correctly I have a Chinese copy and no genuine Lucas part. That is why the measured value is slightly off and therefore the 14CUX gets confused and messes with the long term trim.
Now can I do anything with the CO adjustment or will that not help?
Could I do anything in the cable, like adding a resistor?
Rimmer Bros advertised this AFM as "aftermarket" so at least they were not lying. Where do I get a real one and how do I recognize it?
Have fun!
Marvin
At its most basic the AFM voltage represents the amount of air the engine is drawing, so the ECU then knows how much fuel to add from the fuel map. If the AFM voltage is to high or too low at idle, the resulting map point will be wrong, so the amount of fuel will be wrong. The ECU then tries to correct this incorrect AFM voltage by moving the long term and short term fuel trim- its shutting the stable door after the horse has bolted, as its fixing it after its wrong in the first place. The CO trim has little affect with lambdas' but its always worth setting the DC voltage for the catalyst map to the correct voltage in the first place. The genuine Lucas units have Lucas written on them, but with the amount of fakes around you still cant be sure. Id go for a second hand unit of a Range Rover-
Followed your advise Mark, got myself second hand one.
It works !
But.... As you can see at the pics, it's a rather messy one, but no offense it was given to me. As I had to remove the black panel to resolder the connecter (I have to swap the broken connecter with my old original AFM), I am thinking to take the whole printplate out and put it in my original AFM housing which is pretty clean.
Has anyone done this ? Can I just unbolt the printplate (with the sensor probably mounted at the printplate) and take it out or is this a no go ?
Ronald
It works !
But.... As you can see at the pics, it's a rather messy one, but no offense it was given to me. As I had to remove the black panel to resolder the connecter (I have to swap the broken connecter with my old original AFM), I am thinking to take the whole printplate out and put it in my original AFM housing which is pretty clean.
Has anyone done this ? Can I just unbolt the printplate (with the sensor probably mounted at the printplate) and take it out or is this a no go ?
Ronald
Its is do able- but the pins that project up from the hot wire element don't re solder- from memory its a small spot weld- plus the circuit board has calibration resistors on it- Id suspect these trim against the variable responses of the hot wire element- so... If I was in your shoes Id keep it in one piece, give the body a good clean with alloy wheel cleaner, and then just dust the outside lightly with a satin silver or aluminium paint to make it look nice.
BTW what are doing with the pattern one, sending it back as no good?
BTW what are doing with the pattern one, sending it back as no good?
Edited by blitzracing on Friday 10th October 19:15
I am having the very same smyptoms with my Griff ( de-catted 500). What checks can be carried out on the AFM to determine if its faulty or on the way out ??
The car is also fitted with one of Clives 'Y' piece, and the Lambas are disconnected. A tune resistor is fitted ( as supplied by Clive).
The car is also fitted with one of Clives 'Y' piece, and the Lambas are disconnected. A tune resistor is fitted ( as supplied by Clive).
bomb said:
I am having the very same smyptoms with my Griff ( de-catted 500). What checks can be carried out on the AFM to determine if its faulty or on the way out ??
The car is also fitted with one of Clives 'Y' piece, and the Lambas are disconnected. A tune resistor is fitted ( as supplied by Clive).
Why did you disconnect the lambdas? I was advised that it would run much better with no tune resistor and the lambdas connected. I have a fully decatted 500 with the Clive Y piece, running perfectly.The car is also fitted with one of Clives 'Y' piece, and the Lambas are disconnected. A tune resistor is fitted ( as supplied by Clive).
On the whole you are better off running the white TVR tune and the lambda probes- the green non cat fuel map appears to be a Range Rover one, so not ideal. To test the AFM: (thanks to Mark Adams for this)
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 after the initial "warm up" spike. 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).
Note- This is the critical bit the long term trim gets set to, so it needs to be correct. The next stage is not so important if you just want a basic test.
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 non catalyst systems, 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
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 after the initial "warm up" spike. 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).
Note- This is the critical bit the long term trim gets set to, so it needs to be correct. The next stage is not so important if you just want a basic test.
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 non catalyst systems, 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
QBee said:
Why did you disconnect the lambdas? I was advised that it would run much better with no tune resistor and the lambdas connected. I have a fully decatted 500 with the Clive Y piece, running perfectly.
If I recall, I think I was told that the lambdas were not required when the tune resistor was fitted. Also, the lambdas got damaged during removal and were not replaced. Looks like i need to be replacing them if the engine runs better with them connected. Appreciate your advice.....The Rover V8 engine does run a bit better on a green tune, non catalysts map, BUT it has to be the correct map for your engine- not just some Range Rover map. The fuel chip has no less that 5 fuel maps in it, but it appears only the catalyst fuel map has been changed to suit the TVR with Lambda probes. The only down side to running the catalyst map is the low speed response can shunt slightly and the idle is a bit rougher, but if your car did not do this then keeping the probes is the best bet as its the correct fuel map.
bomb said:
Would you recommend running with the tune resistor IN ( If I recall its set to the white setting), and the Lambdas in too, then ??
If I got a replacement AFM, would this be simply 'plug and play' again ??
Hopefully Blitz will correct me if i am wrong. When I was installing my Clive Y my TVR guy got the firm impression that the white position on the resistor was a position that equated to no resistor, so its purpose was purely to allow you to switch between all the possibilities, including no resistor, without having to remove the resistor. He thus decided that, as he wanted me to run with lambdas, that i didn't need the tune resistor so didn't fit it. hence why mine has no resistor.If I got a replacement AFM, would this be simply 'plug and play' again ??
I have recently bought a bag of spares, which includes a spare 5AM (standard) AFM. If you want to try it just email me your address and I will post it to you. I was told by its previous owner that, as far as he was aware, it worked. I have a 20AM now, so it's no use to me as a spare.
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