Fix/replace 7mgte AFM?

[Alang]

Fix/replace 7mgte AFM?
What is the status of dealing with a bad AFM? It's unclear from my research what the reliable and reasonable ways are to go. Some observations and questions for discussion.
1. There is no complete test to check it. The TSRM test does not tell the story.
2. Is there no good way to clean the mechanism?
3. Saw some concern that an oiled K&N air filter could contribute to AFM failure. True/false?
4. Looks like used ones from a yard (unknown till tried) are $150 - 300.
5. Don't even want to guess what a new Toyota one is, if available.
6. Would a Lexus electronics plug right in to the 7mgte intake housing and is it the right signals?
7. What other substitutions for fuel management can get the job done and keep it done permanently?

 

[turbo4toy]

Be really nice to the members on here and see if a local will cruise by and swap out the electronics from theirs. or you can find one for less than $60 generally here on the forums.

http://www.supramania.com/forums/showthread.php?t=32637

 

[donnys90T]

1) Not true. Easy to test.

2) Somewhat true. It can be cleaned with the right chemicals but they're hard to find and the best one can no longer be made or sold in the US. I'd replace a bad AFM but fwiw I've brought several back to life. Funny thing is most of the ones I test are fine....owners tend to swap parts when they don't know how to troubleshoot.

3) Somewhat true. Oil tends to effect hot wire sensors more than Karmans. Depends on how much oil is used. Most people over clean and over oil K&Ns. Imo you'd have to be nuts to use one in the first place for other reasons.

4) Cheap on ebay/other owners. Unknown condition but see # 2.

5) Very expensive.

6) Yes as long as it's the right one.

7) Maft Pro or a custom translator. If you're handy with electronics you can build one yourself. What I did when I ran 550s.

 

[Isphius]

Fix/replace 7mgte AFM?

1. There is no complete test to check it. The TSRM test does not tell the story. -

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=FI&Page=96

2. Is there no good way to clean the mechanism? - This is bad for the electronics, just used compressed air to clean it, and dont shoot the vortex meter thing directly. Dont use cleaners.

3. Saw some concern that an oiled K&N air filter could contribute to AFM failure. True/false? - possible, no personal experience, But I know liquids are bad for it.


6. Would a Lexus electronics plug right in to the 7mgte intake housing and is it the right signals? I belive the electronics are identical.

 

[donnys90T]

The AFM does nothing more than output a 5 volt square wave with a frequency proportional to air flow. It consists of a flexible mirrored surface, a photo transistor, and an led emitter. The electronics are located outside the vortex chamber and are potted. They're not effected by liquids.

People kill these things because they use solvents that craze the acylic windows of the transistor and emitter or fog the mirror. There are several solvents that won't cause crazing but as I said they're hard to come by. The trichloro 1-1-1 usually found in brake cleaners, carb cleaners, etc is not among them. The most effective way is to vapor clean it with a non-crazing solvent. You don't need a Phd to figure out how to vapor clean something. All the stuff you'll need is already in your kitchen but better is to prevent contamination in the first place.

Testing can be done either on or off the car and I don't mean resistance testing as per the book. The only true way to test it is to measure the frequency of the signal with a frequency counter or a scope and see if it corresponds to the correct airflow in CFM. You can do that with a small fan on the rear of the housing or even a vacuum cleaner if you know the values. I do because I plotted a known good stock AFM and housing while using a calibrated anemometer as a reference. You can also use an automotive hot wire MAF sensor.

If you don't want to bother with all that measure it on the car. The signal should be around 20 hertz at idle and about 50 at 2000 rpm. This is with the stock housing. If the AFM is working at one point the odds are good it's working across it's entire span. The independent air temperature sensor can be check with an ohmmeter using the curve shown in the TRSM. It's nothing more than a thermistor.

You can also calculate what the frequency should be. The formula is f = .2 X v/d, where f = frequency, v = air velocity, .2 is a constant and d = the diameter of the karman pillar, the black thing sticking out of the box.

Btw if you're going to trash your old one I'll take it off your hands.

 

[Alang]

Found CRC Mass Air Flow Sensor Cleaner next to the carb cleaner stuff at Checker. Supposed to be for cleaning MAFs, it has different ingredients than carb cleaner. I have a call in to their tech support to inquire about using it on the 7mgte Karman Vortex AFM.
Some general research indicates that it is useful for regular MAF sensor cleaning. I too may have a problem with my oiled K&N filter.

Heard from their tech support that checked with their chemist who said that they don't have enough/any info about toy/lexus AFM materials to approve its use.

What has been used successfully to clean the AFM and how was it used?

 

[3p141592654]

You want a freon based electronics cleaner. Unless you happen to have an old can on your shelf, you will not be able to buy it (in the US) since it is a banned substance (ozone depleting).

 

[Alang]

What distinguishes freon based cleaner results from others?

 

[3p141592654]

Freon degreasers are generally compatible with most plastics and dry residue free. Replacement cleaners typically attack plastics and can destroy key components in the AFM.

 

[jetjock]

3p is as usual dead on. I was alluding to this in another post with Johnathan. Freon TF (113) is what I use. I have a gallon of the stuff left over from a 5 gallon can I bought years ago when working in semi. The stuff was used all over the industry back then. It can still be had if you look around but it won't be cheap. It's also available in other forms. If the AFM optics have already been wrecked by another cleaner it's not going to work though and this is usually the case.

Most of the CFC refrigerants would also work and are often used as cleaners. CFC-12 makes a great degreaser for example. Same with HFC 134, which is chemically close to 113. The problem is 12 and 134 are boiling at room temperature so whatever you're cleaning has to handle that. Not a problem is you're doing vapor degreasing cause that's what you want anyway. You'd also need to overlook the several violations of the Clean Air Act that'd occur