Thank you for the response!

I blocked the preheat hose flap after the first replacement flap failed.
Over the years I have been through all the air, fuel and electrical systems more than once.

I had sever running problems some years ago and although the AMM Ohms checked out within spec it wasn't until I swapped it out with an AMM from a salvage yard that the major issue stopped.

I was wondering if the AMM cleaner would put that original malfunctioning AMM back into service for a back-up.

I was also wondering if cleaning the AMM would have a beneficial impact on my poor gas mileage. My mileage fluctuates from 15 to 20 mpg in city driving, running sole and unloaded.

In regard to the mileage, the only thing I have not done is replace the O2 sensor after the above mentioned sever running issue. So it could be fouled ... but that does not strike me a contributing to 'fluctuating' mileage.

Then again ... I did just replace a failed in-tank fuel pre-pump. Maybe it has been suffering all the time I have been trying to figure the fluctuating mpg. That pre-pump has not been installed long enough for me to check gas mileage.
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1988 244 DL; B230F; LH-2.2; Manual 5-speed (M47)

Please, don't use isopropanol (rubbing alcohol) or any other such solvents/cleaners as they will leave excessive residue on the wires and vanes. Even then, unless you're using expensive 99% pure, high tech, lab grade isopropanol, there's a lot of water and impurities in it. CRC MAF/AMM cleaners are there for a reason and that's to spray off dust, oils and lightly stuck dirt while leaving very minimal residue. Your Bosch AMM is supposedly self-cleaning using a heating cycle on the wires. Plenty of us are still running around with 25 year old AMMs that have never needed cleaning. As long as that heating cycle is happening and you don't see significant residue on the wires (forget the vanes and screens) and the car is otherwise half-running well without throwing codes for the AMM then I'd leave well enough alone and seek running improvement elsewhere before cleaning the AMM on spec as a preventative or performance improvement measure.

I say all this because I had a flaky AMM in one car and tried to use a quality CRC cleaner. It did make a significant improvement, although in the end it still wasn't good enough so I ended up replacing the AMM (with a reputable rebuilt, much to the dismay of my local Volvo indy). Well, if it could improve that AMM then I thought why not just give the AMM in my other Volvo a clean while the spray can is fresh. Really bad idea! Despite numerous cleaning and heating cycles, it was never the same so I ended up having to replace it as well. Lesson learned, don't muck with an AMM unless you really need to.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Hi,

IMHO,
I would not use it on a hot wire type AMM.
The sensor I’m talking about is the one that actually uses a thin hair like wire, strung in a triangular shape and is held taut between a couple circular anchor loops inside the Venturi.

In my thinking, the wire has to be very fragile because it’s so thin.
Any force from a spray heavier, than air by itself, that gets directed straight onto the wire, in an idea, that it might somehow blow off something affecting the performance of that wire is very dangerous.
These wire type sensors have their own electric self cleaning circuit that burns off contamination. After many heating cycles that wire can actually anneal or temper itself depending on what it’s made of.
Each cycle can make it more susceptible to breaking under fatigue.
So spraying it may instead of cleaning it, will break it!
I wonder if incineration isn’t a bit of overthinking for a minute problem, instead of having more concern of how delicate the design was to evaporate vapors of petroleum oils.
They did change the whole sensor support system later.

It is my thought that the term mass air flow sensor, on the can, is meant to cover the more mechanical flaps or vane sensors!
I can see them getting stuck or sticky with time in their bushings.
The cleaner might help those using a physical moving contact wiper system and electronics inside. If you wet those down you have to make sure it has ample time to completely evaporate.

There are other hot wire sensors that utilize a contact board to mount the sensing films on or have a encapsulated temperature sensing semiconductor on them.
I feel they might benefit from a cleaning, if it was caked on!
Really, Any good maintenance of the engine and the air filter system should keep that from happening!

If you already have a can of it purchased, you have already gone passed any warnings of wasting your money! (-:)

Phil

Is your AMM not functioning? If it works fine it may be best to leave it alone. I believe that it heats up to self-clean.