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Re: Air Mass meter[200/1985] posted by Mike Briney on
Saturday, 12 September 1998, at 3:53 p.m.
I'm having the same trouble as John and suspect the AAM. The car will start, but chugs and runs rich. I have disconnected the plug and that solved the problem for a while. Now when I unplug it there's no change.
The junk yard here want's $150 and I'm hesitant to put out that kind of money on a hunch. Also I can't see how the AAM could be adjusted. Is there a way to test the AAM? how does one adjust it?
Mike
mike
Re: Air Mass meter[200/1985] posted by Don Foster on
Saturday, 12 September 1998, at 11:25 p.m.
Mike --
When you unplug the AMM, the ECU detects this and switches to a fixed fuel flow rate -- one that's more-or-less acceptable for idle and low speed running. Hence the term, "limp home mode". In this situation, as you open the throttle more, the engine runs more and more lean.
Your description sounds more like a failed (or failing) fuel pressure regulator. Or possibly, the small vacuum hose going from the intake manifold to it. In this situation, the fuel pressure rises and the engine runs extremely rich.
This is a guess, but it's possible you could get fooled by unplugging the AMM. The rich condition (from a defective pressure regulator) might be compensated by the lean condition of running with the AMM unplugged and opening the throttle. But as the pressure regulator failed more, the mixture became even more rich, and the unplugged AMM and open throttle still resulted in an overly rich mixture -- so you characterized this as "now when I unplug it there's no change."
I would first inspect the vacuum line for cracks or breaks, and then search for a "loaner" fuel pressure regulator. After that I would try the AMM.
BTW, don't forget that the AMM is very sensitive to electrical surges. Be sure the ignition is off before plugging/unplugging, and it's a good idea to wait about 30 seconds after shutting the key off before unplugging.
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