Date: Fri, 28 May 2004 23:00:36 -0400 From: ma_twain <ma_twainnospamo.com> Subject: Re: Air Mass Meter Question
Mark wrote: > On 27 May 2004 20:17:49 GMT, Dave Hinz <DaveMay2004nospam-creek.net> > wrote: > > >>On Thu, 27 May 2004 18:48:00 GMT, Mark <slycheesenospampam#flashmail.com> wrote: >> >>>Hi Dave, thanks for the response. I'm a mechanical engineer, maybe >>>the style of my post reflects that. :) >>> >>I'm software, but I play electrical and mechanical in my spare time. >> >> >>>I see your point that more needs to work than just the wire burn off. >>>Is the circuitry that performs the control loop in the AMM or is it >>>located in the LH unit? >>> >>I believe the bridge circuit is right in the AMM, since they're >>pretty balance-sensitive and are measuring very low differences >>in resistance. Probably the amplifiers which drive the filament heat >>as well. There's only like 6 pins on the AMM's connector, right? >>(going from memory of my '88) >> > > The connector is 6 pins but it only use 5 of them. My contacts seem > good and clean. But if the cicuitry is inside the meter then I > suppose there could be something flaky in there... I wonder if I can > open it up and check the circuit board for cracks... > > >>>I do think something is failing (not just appearing to fail) because >>>the engine definitely stumbles for a split second, periodically, and >>>it is often accompanied by the check engine light illuminating for a >>>second. >>> >>But where in the feedback loop is the problem? Is it stumbling because >>the AMM is sensing a problem, or is the AMM providing wrong input which >>causes the fuel injection to make it stumble? I'm not sure what the answer >>is. >> >> > > I wish I knew. :) If the manual is to be taken literally then the AMM > is at fault. I did unplug the AMM, run the car, and then checked the > error codes and it showed the same AMM error. But I don't think that > is a conclusive test. > > >>That having been said, a few dozen thousand miles of life on an AMM is >>unusual. I suspect the problem is elsewhere, unless you're just plain >>unlucky. >> > > Well, I have been known to be unlucky. :) I'm thinking of buying a > used one cheap (either off eBay or from a local junker). It seems > like the cheapest way to find out if it's the AMM. Although you never > can be sure when you're testing with old parts... > > Unless of course you or someone else has a better idea. I'd love a > better idea (that doesn't involved spending $400 on _another_ AMM). > > Thanks for your help, > mark > > >>Dave Hinz >> >> > You can try this idea. Buy another Classic Saab of the same year in working order. You can try the AMM from the known working car in your car to see if that fixes the problem. This is how the IBM Computer Engineers diagnosed problems when I worked in data centers. They would keeping swapping parts from a working system into the "broken" system until it was fixed. At least you could try to use it to justify owning another Saab :-)
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