As a quick follow up to my AMM post from yesterday (the car ran magnificently this morning - smoother than butter), I thought I’d share the following.

Tedjs, our GM professori, emailed me a few photos of a modern Mass Air Flow sensor. He uses these shots for his automotive class at Tri-C in Ohio. I’ll attach his comments from my original post as well, as I think they’re quite relevant for anyone looking at a faulty AMM/MAF.

In these shots, you can clearly see the filament I was talking about. The object of the game is to keep that filament at a constant set temperature using an electrical current (think light bulbs). Air rushing past it cools the filament and the change in voltage required to keep it at temperature tells the computer how much air is rushing past, and therefore how much fuel to pump in.

Whilst my old 900 sensor had an adjustment screw, it seems that modern MAF’s don’t. A possible solution for a malfunctioning MAF, in the absence of an adjustment, is to clean it. Following are some comments Ted wrote about cleaning the sensor:

We would let the sensor cool off for a bit and hit the sensing wire with a quick shot of cleaner which is a key point here - a very small amount would clean the sensor if it was contaminated. I only say this because I watched someone use half a can on a sensor and I think it damaged the sensor as brake parts cleaner is a strong solvent. Unfortunately some people live with the adage if a little is good – a lot must be better. Don’t get me wrong – it was entertaining watching him, but that was kind of his method of operation. The guy could not fix a sandwich.

Sometimes if you would clean them the problem would come back and the sensor would have to be replaced. The sensor wire generally gets about 100 degrees Fahrenheit (37.78 degrees Celsius) higher than ambient air temperature so I think things would get cooked on it occasionally.

CRC recently introduced a mass air flow cleaner here in the USA that is for sale at most auto parts stores. It is less caustic than brake clean and is less likely to damage the sensor housing and attack the electronics. I know some shops are selling it as a maintenance service as newer cars are so reliable they have little to do in terms of routine maintenance, but I have mixed feelings about that. That sensor is expensive and cleaning a clean one might damage the filament. Sort of a ‘if it ain’t broke – don’t fix it’ approach if you know what I mean.

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Inspired by my successful venture yesterday and a desire to learn more, I’ve just ordered a Bentley manual for the Saab 900 16V to go with my Haynes manual that’s already on it’s way from Elkparts.

The Bentley manual seems to be pretty well regarded, so I’m sure it won’t hurt to have it on the shelf as well. There’s probably areas of the car that one manual handles better than the other.

I don’t think I’m going to be replacing timing chains or anything like that, any time soon. But it’s fun to learn, especially with our young bloke hitting 17 and looking for a car to buy too (He’s scoping out Honda Preludes).

He’s got a natural aptitude for this sort of thing so I’ve got to keep up!!

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