Discovery 1 MAF 14 CUX

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hi_arshard

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Hi guys, anyone has experience with discovery 1 , V8, MAF - 14 CUX. Car is running very rich black smoke and huge fuel consumption. When checked the reading from MAF on idle it is 12 to 13v which is very high. it’s supposed to be 1.3 to 1.5v. Appreciate any leads what need to be checked next….

I have checked with 3 different MAF’s
 

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Hi, make sure that you measure between ground and the blue/green wire not on the supply(brown/orange) and if on blue/green you get that 12V with all 3 MAFs means there is a short in the harness to battery supply. Disconnect the MAF and measure in the unplugged connector to blue/green wire as well then report the result
 
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Stanleysteamer said:
If it is like the TD5 engine, the ECU will then switch to a pretty good map which will drive OK.
I did this ages ago on my TD5 and it drives just fine. No matter which MAF I fitted they all went fubar, at silly expense, hence the reason.
Click to expand...
The petrol engines are working on a completely different principle based on stoichiometric fuelling calculations where the air flow reading si vital not like on a Td5... one with 14CUX ECU with MAF unlugged would go on a default based on TPS angle which is a kind of "limp mode" so not the way to manage this issue...
 
sierrafery said:
The petrol engines are working on a completely different principle based on stoichiometric fuelling calculations where the air flow reading si vital not like on a Td5... one with 14CUX ECU with MAF unlugged would go on a default based on TPS angle which is a kind of "limp mode" so not the way to manage this issue...
Click to expand...
Correct mate… it’s on total limp mode with black smoke fuel consumption was very bad and no power as well. I found the issue, when I replaced the engine the garage guys broke the MAF connector harness, now this can be connected both ways… so it was connected on the wrong side. Now I am getting reading from MAF.
 
sierrafery said:
Hi, make sure that you measure between ground and the blue/green wire not on the supply(brown/orange) and if on blue/green you get that 12V with all 3 MAFs means there is a short in the harness to battery supply. Disconnect the MAF and measure in the unplugged connector to blue/green wire as well then report the result
Click to expand...
Thank you for the input, the issue connector was connected other way around. Following are the readings which connected and on idle speed,

Wire color
Red/black
0.06

Blue/Green
1.64

Orange/Brown
13.7

Blue/Red
1.94

Kindly advise if this readings are correct for idle speed.
 
Is your's 3.5 or 3.9 engine, cathalyst or not? ... and as you have now MAF reading you should measure across the red/black(ground from ECU) and all others cos that's relevant albeit your readings at idle seem OK in general
 
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sierrafery said:
Is your's 3.5 or 3.9 engine, cathalyst or not? ... and as you have now MAF reading you should measure across the red/black(ground from ECU) and all others cos that's relevant albeit your readings at idle seem OK in general
Click to expand...
Hi, thank you for your input.

It’s a V8 3.9 no catalyst
sierrafery said:
Is your's 3.5 or 3.9 engine, cathalyst or not? ... and as you have now MAF reading you should measure across the red/black(ground from ECU) and all others cos that's relevant albeit your readings at idle seem OK in general
Click to expand...
Hi, thank you for your input.

It’s a V8 3.9 No catalyst.

You said (ground from ECU) where do I find that ?

In parked, full throttle I see black smoke. Also I feel lack of power.

Note: recently I have replaced the engine, since then I am struggling with all these issues.

Thanks.
 
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sierrafery said:
The petrol engines are working on a completely different principle based on stoichiometric fuelling calculations where the air flow reading si vital not like on a Td5... one with 14CUX ECU with MAF unlugged would go on a default based on TPS angle which is a kind of "limp mode" so not the way to manage this issue...
Click to expand...
I did say "IF".....................!
 
Get a rovergauge cable and you can see all the reading direct from the ECU - exactly what it's seeing.

There are mutliple MAF readings you have to look for. The Idle CO is one thing, but if the MAF isn't working, then the CO adjustment means nothing anyway The CO adjustment doesn't alter the MAF readings, just the ECU fuelling adjustments at low load/RPM). There is a test on the MAF output signal, where it should initially spike, then settle down very fast after turning on the ignition, then once started, the voltage varies with airflow. I can't remember the pins or the readings now though (Initial spike to 0.8V? then quickly settles to 0.3x volts? etc) Mine wasn't settling down, but hanging in the mid range, fixed with a good used unit.

I can't find the details of the test right now though!

You also need to know if the temp sensor is behaving. Colder engine has more fuelling.

Honestly - Rovergauge cable (build or Buy) and the free software makes diagnostics easy-peasy.
 
Oh wait - found notes:

Pin 2 (red/black or black) and Pin 3 (blue/green or green). Switch on ignition (but not starter) and expect to see 0.30 - 0.35 volts. Switch off wait 10 seconds and then switch ignition on again. Airflow signal should immediately go to 0.30 – 0.35 volts.

If higher (0.5 - 0.8) and takes few seconds to drop: is bad
Readings over 2.0 at idle instead of around 1.7 volts for a 3.9 is bad.

I've only tested my one, which didn't do what these notes said, and after replacing it, I can less rich and also better idle, though I had other issues to sort out too.

Note - those are NOT the CO adjustment readings! It's MAF output.
 
AllanWorms said:
Oh wait - found notes:

Pin 2 (red/black or black) and Pin 3 (blue/green or green). Switch on ignition (but not starter) and expect to see 0.30 - 0.35 volts. Switch off wait 10 seconds and then switch ignition on again. Airflow signal should immediately go to 0.30 – 0.35 volts.

If higher (0.5 - 0.8) and takes few seconds to drop: is bad
Readings over 2.0 at idle instead of around 1.7 volts for a 3.9 is bad.

I've only tested my one, which didn't do what these notes said, and after replacing it, I can less rich and also better idle, though I had other issues to sort out too.

Note - those are NOT the CO adjustment readings! It's MAF output.
Click to expand...
+1... I digged too and found the following:

Airflow Meter(14CU/CUX)​

This is one of the key fuel-metering elements of the system. 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 0.5 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 (4.0 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 (4.0 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.
 
sierrafery said:
+1... I digged too and found the following:

Airflow Meter(14CU/CUX)​

This is one of the key fuel-metering elements of the system. 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 0.5 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 (4.0 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 (4.0 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.
Click to expand...

AllanWorms said:
Oh wait - found notes:

Pin 2 (red/black or black) and Pin 3 (blue/green or green). Switch on ignition (but not starter) and expect to see 0.30 - 0.35 volts. Switch off wait 10 seconds and then switch ignition on again. Airflow signal should immediately go to 0.30 – 0.35 volts.

If higher (0.5 - 0.8) and takes few seconds to drop: is bad
Readings over 2.0 at idle instead of around 1.7 volts for a 3.9 is bad.

I've only tested my one, which didn't do what these notes said, and after replacing it, I can less rich and also better idle, though I had other issues to sort out too.

Note - those are NOT the CO adjustment readings! It's MAF output.
Click to expand...
Hey Allan,

Thank you very for the information shared it was very helpful really appreciated.

I have done the test and following are the results.

Mean time I have ordered the cable for the USB FDTI cable for the Rover gauge, will be working on that soon.

Reading from MAF,

Red/Black - ground
Blue/Green - air flow signal

Reading ignition on - 0.22 to 0.24
Idle cold 1.65 to 1.67
Idle hot - 1.58 to 1.62

Idle CO mixture adjustment
Red/Black
Blue/Red
Idle 1.87

As you mentioned the CO adjustment on the MAF, this adjustment is sealed and unable to access the adjustment screw. Is there a way to open this or some comes sealed ?

Also I have black smoke issue, if I press the throttle full I see thick black smoke.

Appreciate your input…🙏
 
hi_arshard said:
Hey Allan,

Thank you very for the information shared it was very helpful really appreciated.

I have done the test and following are the results.

Mean time I have ordered the cable for the USB FDTI cable for the Rover gauge, will be working on that soon.

Reading from MAF,

Red/Black - ground
Blue/Green - air flow signal

Reading ignition on - 0.22 to 0.24
Idle cold 1.65 to 1.67
Idle hot - 1.58 to 1.62

Idle CO mixture adjustment
Red/Black
Blue/Red
Idle 1.87

As you mentioned the CO adjustment on the MAF, this adjustment is sealed and unable to access the adjustment screw. Is there a way to open this or some comes sealed ?

Also I have black smoke issue, if I press the throttle full I see thick black smoke.

Appreciate your input…🙏
Click to expand...

Correct, the CO adjusted is sealed, that because the EFI ECU looks after everything on the 3.9… so no need to touch.

Although the early 3.5 RR was different, it had caps that could be prised off and they even had a part number.

My 3.5 RR started having thick black smoke starting from cold, It was then a common ECU issue, so as my LR dealer couldn’t find a replacement ECU anywhere, I removed the ECU and took it the Lucas factory and they put it on a test rig and found host of component failures, and did a repair with updated parts in a couple of hours. Job done and never had an issue again.

My recent CO test at an MOT test below, not bad for a 27 year V8 😊
 

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You can drill a small hole in the cap and pull it out with a screw, but it's the LAST thing you should be playing with, for you issue.

The CO adjustment only trims the basic fuelling at low RPM and load... and if you have Lambdas, they take over that control anyway. The CO adjustment just sets a starting point.

I see you have no catalyst - is that factory? If so, you should have no Lambda Sensors either???

Having a CO trim set to 1.87 isn't right for a non-cat car... but I still think you need to see what the temp sensor is showing - if it thinks the coolant/engine is cold, it'll overfuel.

If you DO have Lambdas, exhaust leaks and/or missfires make the ecu *think* the mixture is lean, so it'll run richer too.

The cool thinkg about RoverGauge, is that you see what the ECu actually sees - not what the MAF is reporting, or how a sensor measures: at the end of the day, what the ECU actually sees, is what it uses for calcs, so it really makes things a lot easier.

With Rovergauge, you can adjust the CO trim reading live (while using a non-cat tune resistor), but really should be done to a sniffer measurement.

You MAF air flow readings look plausible.

I suspect you are most likely to have a coolant temp sensor issue, or extra fuel from leaky injectors etc. It would also pay to check the fuel pressure, and especially the diaphragm in the regulator - if the regulator is leaking fuel into the intake, it'll be super rich too.

Going forward, it's possible the MAF has been exchanged with one from a cat-equipped car - hence the 1.8ish reading. If you DON'T have Lambdas, it's possible you'll need to adjust it, but it is supposed to be done with an exhaust sniffer.
 
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