Date: Fri, 05 Mar 1999 21:03:59 -0800 From: Justin VanAbrahams <jvanabranopsam.com> Subject: Re: Fuel control computer
erogers wrote: > > The car is a 1987 Saab 9000 , 5 speed manual . That is the impression we > have , that it's a fuel mixture problem . I believe that my dad look at the > 02 sensor. He measured the resistance on the leads and got what he expected. > Is their a way to determine ( other than measuring resistance ) whether the > sensor has gone bad ? If the sensor and contacts are good then I would > expect that the computer is bad . We are trying to figure out how to > separate the two possibilities . Any Ideas how we can test this ? > Ed Okay... on '87 model year cars, LH 2.2 is used. It is basically a very 'stupid' management system, in that it has no real ability to detect or diagnose faults. It really can only tell when a component is seriously malfunctioning, or when it is completely missing... :) In this case, the air mass meter is most likely at fault. Although there is a test proceedure, I've never found doing so it to provide reliable results. Your best bet is to find a known good one and swap it out - doing so is very simple. Unfortunately, I'm not aware of any real possibility of separating the two components to isolate a problem. Since you've already done the O2 sensor, chances are (and I'd say always were), that the AMM is failing ... I will say that your stumble coming off idle sounds *very much* like a failing air mass meter, and if the car has more than 100k or so on the original unit, it would not be surprising that it's the source of your problem. There are three individual tests for the AMM, and none of them guarantee that it's working... if you want, I can post or email them to you... The easiest one is to check the burnoff feature - disconnect the AMM from the airbox, start the car, rev it to about 2500rpm, hold it for a few seconds, and turn off the engine - watch the AMM and in a few seconds you should see the three wires glow pretty brightly. If they don't, you've got a hosed AMM. -Justin
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