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x2 Posted by Justin VanAbrahams [Email]  (#32) [Profile/Gallery]
(more from Justin VanAbrahams) on Fri, 10 Jun 2016 15:50:24
In Reply to: Re: New Parts...Same Problems, Landjet   [Profile/Gallery]
, Fri, 10 Jun 2016 15:36:15
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There is essentially no way for the end user to check the AMM. The burnoff feature is just one feature, and has no real bearing on its ability to operate the car. Saab specified using a CO detector in the tailpipe with known-quantity input to adjust it. With those tools, you can get it ballpark. Without them, you're lost.
The AMM works by keeping the hot wire at a specific temperature in the face of changing airflow and then reporting the correction factor back to the ECM as a voltage signal. If you don't have the ability to provide a fixed airflow and monitor that voltage change, you can't do anything to troubleshoot the AMM much less fix it.
The LH 2.2 AMMs are horrible because they change behavior as they age and the ECM has no way to adjust for it. Eventually the AMM just drifts out of usefulness and then you're hosed, but the period between "peak operating" and "total failure" is HUGE. The slow degradation will typically go unnoticed until it totally fails because it happens slowly over years and years. Anecdotally, until recently, I never heard much about totally failed AMMs, but it seems to come up more and more. I think they're all finally drifting out of any usefulness.
If you have a junkyard near you, just get a replacement AMM. Working or not is less important than just different - if it changes the behavior, you have new information. If there is no change, it's probably not the AMM. But, it's probably the AMM.
It could be the O2 sensor. Have you put a multimeter on it to see what it's doing? It typically takes about a few minutes at idle before the O2 sensor is doing useful things... it takes the heater that long to bring it up to temp. However, an old O2 sensor can take longer if the heater has failed - which is fairly common. You'll know when the O2 sensor is doing anything when the voltage starts swinging around. If five or six minutes pass and it's still not swinging, you at least have a bad O2 sensor heater and maybe an entirely bad sensor. They're $30, I'd just replace it.
You can remove the distributor from the head, remove and then properly ground a spark plug, turn on the ignition, and spin the distributor by hand. **UNPLUG THE FUEL INJECTORS.** You should see spark and see the tach bounce and if you can spin it fast enough (use a low-speed drill) you should hear the fuel pump run. If you don't get this, you have a problem with the ignition system - maybe the Hall sensor, maybe the ICU, maybe the stupid ignition amplifier in the fuse panel. Just jumper that thing and get it out of the equation.
posted by 12.195.130...
, Sat, 11 Jun 2016 10:31:48, Fri, 10 Jun 2016 13:28:56, Fri, 10 Jun 2016 13:26:29, Fri, 10 Jun 2016 15:36:15, Mon, 20 Jun 2016 15:49:41, Fri, 10 Jun 2016 15:50:24 <-- Viewing This Message
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