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Old 04-11-2006, 07:03 PM   #1 (permalink)
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Default How to clean your MAF sensor?

http://www.fordscorpio.co.uk/cleanmaf.htm
The above is a link to a "How to clean your MAF sensor", though it was for a Ford. I decided it might be the problem I was having, so since I had replaced mine, I took the old one and cleaned it. It seemed like I had nothing to lose in doing it. Right off, the Disco is running better than it has since I've had it. No more missing and lots more pep. Time will tell on mpg and whether any codes come back, but I went through a couple of drive cycles and no check engine light.

The proceedure was fairly simple. You pull the sleeve out from the end with the screen, remove the screen, and spray the two wires to clean them. The article suggested Carborator Cleaner, but I used CRC electrical cleaner. Hope that helps someone.
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Old 04-11-2006, 08:40 PM   #2 (permalink)
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Good article. Glad I don't have a MAF even that use to be my nickname in my teenage years. Was due to my surname of Matthews rather than me being clogged up and having a hot wire.

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Old 04-14-2006, 08:07 PM   #3 (permalink)
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Thumbs up Done it with my old car....

use good electrical cleaner or brake cleaner when cleaning. Allow plenty of time for the cleaner to evaporate and it does do the job. I did not disassemble the MAF. I just flooded it and made sure all the excess drained out and then I let it airdry in the sun for 15 or 20 minutes. Usually I also cleaned out the intake manifold and hit the butterfly valve as well.

I used to do it on my old Mitsu Mirage and it kept the acceleration quick and peppy. I think I did it at least once every springtime and also cleaned the intake ducting. Use the brake cleaner for that and it comes out very very clean.

When the weather gets more moderate, I guess I have another chore to do on the D1.

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Old 04-18-2006, 05:54 PM   #4 (permalink)
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Could not get the article to open. Is the MAF the same as the oxygen sensor? I have a 1996 SD. Not an everyday driver but use it when not driving the Company car. Got it at the end of last year. Went form Chevy V8 to Rover V8 and noticed significant difference in power. Maybe this will help.
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Old 04-18-2006, 06:29 PM   #5 (permalink)
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Default Here is the gist of it..minus photos.

(LR folks said any hydrocarbon will ruin the MAF sensor (just downstream of the air filter, but I've cleaned two and they both work fine. LR makes about $600 each, so I'm not sure how objective they are..)

Vehicle All except 12V
Year All
Mileage Any
Repair Cost £4 approx
Repair Part(s) Carb or Brake Cleaner
Cleaning the Mass AirFlow Sensor (MAF)
See also (Testing the MAF)

The MAF is a key engine sensor that detects the volume of air being drawn into the engine. In older engines the pressure of the air in the inlet manifold was detected using a MAP (Manifold Air Pressure) sensor, however with the development of these new, highly accurate MAF sensors, the engine management system can take advantage of a more accurate knowledge of the load of the engine. In the case of the Scorpio, the EEC-V also uses this data to decide upon the operation of the automatic gearbox: several owners have reported gearchange problems and torque converter slip that we discovered was related to a dirty MAF and NOT a problem with the gearbox. Note that this does not cure the Cattlegrid effect which is a fault in the gearbox torque converter and nor does it cure problems associated with damaged wiring looms.

The MAF sensor, tucked away neatly inside the air inlet trunking, is easy to forget. Indeed, unless it fails it will never normally be removed or cleaned. Much like the INJectors, it is not examined during a normal service.

There is mounting evidence that a dirty MAF sensor can cause gearbox malfunctions, such as reported incorrect ratio errors, loss of 4th gear or torque converter clutch (TCC) operation, even on gearboxes recently overhauled at great expense. At first I suggested that the MAF should be replaced - but Martin S suggested cleaning the sensor wires instead, a simple operation taking ten minutes. After this, normal service was miraculously restored.

But how can it get dirty? Surely there is an air filter to keep it clean?

Well, yes there is, but air has to be allowed through, and with it microscopic pollen and other organic material which burns when it comes into contact with the sensor wire, which is maintained at 200 degrees C. The MAF electronics measures the amount of current required to keep the wire at this temperature, against the cooling effect of the inlet air flowing past it. Hence the current required is a measure of the actual airflow.



As the MAF inevitably becomes coated in soot the readings for the Powertrain Control Module (PCM) become less and less accurate, but the PCM has no way of knowing this. It must accept the reading, and since the PCM uses the MAF to determine airflow for fueling, idle (with the IACV), the torque converter clutch and gear scheduling (see EECV) it is not surprising that the gearbox begins to produce errors. The PCM is selecting gears which are not actually suitable for the work which the engine is doing.

Tools Required.

Carb Cleaner or Brake cleaner, 10mm socket (depending on model), flat bladed screwdriver, large crosshead screwdriver (depending on model)

On some Scorpio engines the MAF is placed between two rubber inlet hoses. these are removed by loosening the hose clips on each side. The connector is removed from the MAF (don't pull the wires - ease the multiplug off while pressing down the securing clip.)

On the 24V it is best to remove the top of the air filter box and after loosening the hose on the other side, take the MAF complete with the cleaner box to the bench, where it is easier to remove the four 10mm bolts. Remove the rubber O ring carefully and lay it to one side - it fits in the groove on the air filter box.



Above. To my knowledge this is the first time this sensor has seen the light of day in 96,000 miles. The inside shows no sign of dust. The small circular housing contains the sensor wires and were covered in soot.




Above, the internal wires of the sensor. One is the hot wire and the other a precision resistor. You can see how fragile they are - don't drop the sensor onto a concrete floor, or prod about in there with anything - if the wires break the MAF is junk and they are approximately £100 to replace so TAKE CARE. This is the inlet end of the sensor - the housing in which the wires sit is open at the other side, allowing air through.

After a couple of squirts of carb cleaner, which very quickly evaporates, the sensor wires were bright and shiny again. I replaced the rubber O ring with a smear of light oil and then bolted up the MAF sensor to the air filter box. I then lubricated the rubber hose with another smear of oil and pushed the other end of the MAF sensor into the inlet pipe and re tightened the hose clip. Reconnecting the multiplug finished the job.

Result? Smoother running on tickover, and smoother throttle response. Just in town the gearbox feels smoother, but a longer run is needed before I can tell the real difference. I did not experience any gearbox errors beforehand, but other owners, (Oliver and Pete) state that it produced a dramatic difference in their gearboxes.

NOTE: take care that the sensor hoses are properly sealed against leaks.


As a result of the discussions about MAF, one owner decided to try this himself. Here is his report. Here is the link to the .dat file for the OBD2 readings.










I had a bash at cleaning my MAF with the aid of OBD graphing if anyone is interested in what happened when I did:

Test starts, my MAF is reading 0.524 lbs/min airflow, the car is at 850 rpm and cold, the A/C is switched off.

The flow rate gradually reduces, and as the engine warms up goes to 0.508 and down below 0.500, reaches 0.497.

Now the engine has warmed up to normal and the MAF is reading 0.440 lb/min rate. Time to rev it up a bit.

At 2397 rpm th MAF is reading 1.366 lb/min and returning the revs to idle, at 872 rpm the MAF is reading 0.413 which is about as low a reading as it has given so far.

More revving, 3087 rpm gives 2.157 lb/min, back to 0.420 at tickover. This seems to be stable now at low 400 thousands of a pound per minute at tickover.

Putting on the air conditioning, and the MAF reading rises to 0.575 at 850 rpm. Don't know why the AC causes the reading to rise, unless it is to do with the cooling effect on the airbox which is near the AC valve.

AC back off, 857 rpm and 0.407 lb/min.

Of to mess with the MAF...

Airbox off first, five screws and a couple of clips hold it to the bottom of the airbox and the MAF itself, I took the opportunity to replace the air filter at the same time although the old one looked ok really, and I kept that as an emergency spare. This may have affected airflow in the sense that more air will pass through the new filter than through the old one. As will be seen, the opposite effect is observed, which should imply either the filter made no difference or the cleaning was even more significant.

A jubilee clip holds the MAF to the next element in the airflow route, some sort of cube with big air hoses. There is also the electrical connection to the MAF, which is the usual ford type with a retaining clip, press in the metal wire clip and the connection comes off easy as anything.

The MAF is a short tube with a cross member, one end of which has a small tube containing the two wires which are the sensors giving the reading. When I get this off, the wires are a dull grey or brown, being quite hidden away the colour isn't obvious.

Ok, so out with the "carb and injector cleaner" spray can, I fasten a little tube on the end of the nozzle, test it, and then spritz away liberally. Cleaner drips out of the other end of the sensor cross member, but the wires are miraculously undamaged.

But not quite clean, now that the wires and chamber are mostly shiny silver, a few dregs of dark matter remain, so some more fizzing with the spray can until they are completely clean. Then a couple of squirts down the tube into the engine, clean up the MAF fittings and a drop of light oil to ensure a tight seal around the rubber ring and the whole thing goes back together the way it was to begin with. This isn't entirely trivial, the air boxes are flexible and move to the right as you have the air filter box off, so you have to shove it all back to the left before it fits properly, not too hard to do but worth expecting this.

Also, don't forget to connect the electrics, this is probably the one that will be forgotten if anything is. Who knows what happens if the maf isn't wired up?

Ok, fired up again, the OBD is reporting 0.418 at 860 rpm. This is unchanged, at first glance, but the engine has had the opportunity to cool off a bit.

Revving things up, at 1947 rpm the reading is dead on 1.000 and at 2962 has risen to 1.460 lb/min and these figures are considerably lower than they were before,

Returning to tickover, 867 rpm and the airflow is now 0.377, the lowest reading so far. Rev up and down, the setting is still on 0.377 at 868 rpm, a lot more consistent than before but that's probably just chance.

Air conditioning on, and the reading goes to 0.554 at 861 rpm. Again, this is a bit lower than before. Running with revs and the AC on, the OBD shows 1.858 lb/min at a steady 3000 rpm, higher than with the AC off, lower than with the AC off and before the cleaning.

Turning off the AC, at 2910 rpm the MAF is measuring 1.440 lb/min.

Conclusion of all this is simple enough. The MAF contains two wires, one is very hot and any muck entering the unit will basically burn onto the wire and reduce its function. Basically, more heat must be pumped into the wire to keep it at the set temperature because it also has to heat up the dirt, this translates to the sensor imagining that more air is passing by the wire to make it that much cooler.

And, since this unit is not cleaned by an automatic process or during routine servicing, it is inevitable that over the years the MAF will become gradually dirtier and this will cause it to read more air passing into the engine than is really happening, and the fancy automatic computer control metering the fuel and everything will be misled and will obviously pump more fuel into the engine than is actually needed. Conclusion, clean your MAF regularly because it will become inaccurate and it won't be cleaned by anyone else, and the effects of a major engine sensor giving readings that are up to 30% or more higher than they should can obviously be quite extreme, e.g. strange autobox selection profiles are just the tip of the iceberg, and heavy fuel consumption ought to be expected.








Copyright © 2002 www.fordscorpio.co.uk
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Old 04-18-2006, 08:41 PM   #6 (permalink)
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Cleaned my MAF sensor today. Broke it down into its 3 component parts (intake, body and "exhaust"), not a big deal, you just have to be careful with the cardboard gaskets so you don't break them. It's the only way that you're going to get at the wire elements in the body - there's no real way to flood the sensor with carb cleaner without disassembly. Wiped down with a soft cloth all the aluminum surfaces - 10 years of grime is pretty ugly. The wire mesh at the entrance of the sensor needs replacing - that went on the wish list.

I hit the throttle body and butterfly valve with cleaner for good measure and washed the rubber tube in warm soapy water.

The results: great!

The motor was idlying smoothly already (remember I just had it tuned, new plugs, new MSD coil and Magnacor 8 mm wires), but, if you can believe it, it's even smoother now.

I'm hoping this will fix the rich mixture I can see carbonized on all 8 of my plugs.

Go for it!
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Old 04-18-2006, 09:12 PM   #7 (permalink)
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MG

Did this solve your clack clack problem with the engine?
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Old 04-19-2006, 07:16 AM   #8 (permalink)
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Quote:
Originally Posted by texasrover
MG

Did this solve your clack clack problem with the engine?
Nope - still clack, clacking...

Pulled the plugs to see if they had anything to say - they were uniformly blackened by carbon fouling (over rich mixture).

I'm still on the war path for the injectors...

Thanks for the concern!

Peace,
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Old 04-19-2006, 07:19 AM   #9 (permalink)
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OK guys- time out for a second! DON'T go spraying carb cleaner on that thing! There is a cleaner available that won't damage the sensor, made specially for cleaning induction parts. Don't use brake cleaner- that stuff is WAY too harsh as are most carb cleaners. Look for the cleaners that are safe for coated throttle bodies and they are the ones that won't damage the MAF.
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Old 04-19-2006, 03:28 PM   #10 (permalink)
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Default On the running rich

If you haven't, it might help to replace the short vacuum hose from the fuel regulator and clean the oil separator inside the hose(actually in the valve cover) on the right valve cover.
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Old 04-19-2006, 03:55 PM   #11 (permalink)
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Quote:
Originally Posted by Tuco
Could not get the article to open. Is the MAF the same as the oxygen sensor? I have a 1996 SD. Not an everyday driver but use it when not driving the Company car. Got it at the end of last year. Went form Chevy V8 to Rover V8 and noticed significant difference in power. Maybe this will help.
No. The MAF sensor is in the intake hose between the air filter and intake. That rectangluar thing that says Lucas upside down.

The oxygen sensors are on the exhaust system, down below the engine. To see one, look at the exhaust bung next to the steering column and you will see something that looks like a small cigar with a pigtail coming out of the bung. In the North American Spec, you got four, two on the bung and then after the cat, two more.
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‘The Education of Henry Adams’ (1907) ch. 25
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Old 04-19-2006, 04:10 PM   #12 (permalink)
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Thanks, still picking up bits of information. This vehicle is a little different from most others I have owned. Had a less than desirable experience with "foreign" vehicles many years ago. My first car was a 1969 Truimph Spitfire ( in 1980), would not run if it rained! Moved on to a 1969 Camaro shortly there after. Probably the best car I have ever owned. Been more of a US domestic buyer since but I have always, always wanted Land Rover. Willing to work through the problems. Thanks for the advise.
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Old 04-19-2006, 04:27 PM   #13 (permalink)
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Arrow Time for a Recommended list of cleaner...

Quote:
Originally Posted by Muddy Oval
OK guys- time out for a second! DON'T go spraying carb cleaner on that thing! There is a cleaner available that won't damage the sensor, made specially for cleaning induction parts. Don't use brake cleaner- that stuff is WAY too harsh as are most carb cleaners. Look for the cleaners that are safe for coated throttle bodies and they are the ones that won't damage the MAF.
If you got some namebrands of safe sprays you can drop for the guys on the list who cant read the fine print on the side of the can, that would help. I used Gum-out and one other that slips my mind at the moment that I found worked just fine.

Adam in NYC USA
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Nothing in education is so astonishing as the amount of ignorance it accumulates in the form of
inert facts.
‘The Education of Henry Adams’ (1907) ch. 25
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Old 04-19-2006, 04:32 PM   #14 (permalink)
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Quote:
Originally Posted by Tuco
Thanks, still picking up bits of information. This vehicle is a little different from most others I have owned. Had a less than desirable experience with "foreign" vehicles many years ago. My first car was a 1969 Truimph Spitfire ( in 1980), would not run if it rained! Moved on to a 1969 Camaro shortly there after. Probably the best car I have ever owned. Been more of a US domestic buyer since but I have always, always wanted Land Rover. Willing to work through the problems. Thanks for the advise.
Get your paws on the following for best defense:

Haynes Land Rover book for Discovery ISBN 1 85960 708 x
Workshop Manual in print or at least the RAVE CD for IBM PC
Step by Step Land ROver Discovery (and Range Rover) Service Guide (Porter Publishing) ISBN 1-899238-19-0
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Nothing in education is so astonishing as the amount of ignorance it accumulates in the form of
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‘The Education of Henry Adams’ (1907) ch. 25
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Old 04-19-2006, 05:26 PM   #15 (permalink)
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Default How did you take the MAF apart?

me.guevara..How did you take the MAF sensor apart? Did you drill the rivets on the face plate out and then disassemble. So far, I've only taken the front screen out of the way to clean the two sensing wires. Thanks.
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