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Re: AMM question Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Wed, 11 Jan 2006 07:06:46
In Reply to: AMM question, Joonyerr, Tue, 10 Jan 2006 20:52:34 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The filament 'lighting up' means the burn-off function is working. This means the AMM is getting power, and is connected to the ECU. There is other circuitry in the AMM that actually reads the signal. That can be bad and the burn-off function be good.
The AMM doesn't control idle that much. The very first place I'd look is for vacuum leaks. All cars have at least one, if not more. And those cause bad idle. Look for cracked or broken hoses. Keep looking.
Next, I'd make sure that the spark plugs are in good shape and the gap is right. If they look dirty or old, replace them. Also make sure that the timing is OK, and the cap and rotor look good. If the spark plug wires are over three years old, replace them. Essentially, make sure the engine is tuned up before you start chasing problems. Otherwise, you're chasing more problems than you have to. I assume the fuel and air filters are in good shape.
The spark plugs will also tell you about engine operation - if you see evidence of lean running on the plugs, suspect vacuum leaks. If they look rich, think leaky fuel pressure regulator (FPR).
After that, as the others have said, I'd check the AIC. It, after all, controls idle.
When the AMM starts to flake out, you don't usually see it in idle, although you can. Typically the car will have very poor off-idle response; namely, as you hit the gas pedal to accelerate from a stop, the engine seems to ignore you until you get your foot into it. If the engine has good throttle response, then the AMM is probably OK.
Note about the 380 ohms for the AMM. In AMM's that have an adjustment (an adjusting screw), 380 ohms is what the factory recommends as a Starting Point. These AMMs must be adjusted for optimum performance and low emmissions. But you need to start somewhere, and the factory has determined that at 380 ohms, the vast majority of engines will at least run. Maybe not well, but run. It takes a running engine to adjust the AMM. And all you're looking at when you see 380 ohms is the resistance of the adjustment potentiometer. The rest of the AMM could have crumbled into dust and you'd see 380 ohms, if that's where the potentiometer is set.
posted by 192.249....
, Wed, 11 Jan 2006 07:06:46 <-- Viewing This Message
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