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Re: Well, my problem is a steady idle that i don't Posted by Cmyles [Email]  (#1126) [Profile/Gallery]
(more from Cmyles) on Wed, 4 Jan 2012 14:26:03
In Reply to: Well, my problem is a steady idle that i don't, Nicknick  [Profile/Gallery]
, Wed, 4 Jan 2012 11:29:25
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So the AMM is good (doesn't hunt in the SPG) but when you put it in the CV the idle hunts.
The AMM provides the course signal that tells the ECU how to adjust the fuel trim (injector pulse duration). With no signal from the AMM, the "incoming air signal", opening the throttle would cause the engine to stumble and die. The O2 sensor tells the ECU, based on the amount of oxygen in the exhaust stream, how to fine tune the fuel trim to achieve ideal combustion. That's "closed loop" operation. The O2 sensor must get hot before it can provide an accurate signal and that takes a few minutes so prior to that the fuel injection system operates in "open loop" mode. It uses the signal from the AMM and a "map" or standard program to adjust the fuel trim. A vacuum leak throws a monkey wrench into the system by creating a lean mixture that is inconsistent with the AMM signal (and O2 sensor in closed loop mode). The ECU constantly tries to rationalize the two and the result is hunting. AMM signal defects (evident in open loop mode) can be neutralized once the O2 sensor is hot and smoothing out the fuel trim. Vacuum leaks persist in affecting the trim, and cause hunting, regardless of mode or engine temperature.
Depending on when your CV was hunting, only when cold versus all the time, and assuming now that the AMM is good, then I'd say look for a vacuum leak (how about the intake manifold gasket?) or suspect the O2 sensor. You might suspect an ECU defect but that's a real long-shot.
posted by 198.233....
, Mon, 2 Jan 2012 15:02:06, Wed, 4 Jan 2012 11:29:25, Wed, 4 Jan 2012 14:26:03 <-- Viewing This Message, Wed, 4 Jan 2012 16:43:29, Tue, 3 Jan 2012 09:43:40, Mon, 2 Jan 2012 19:57:52, Mon, 2 Jan 2012 17:34:19, Mon, 2 Jan 2012 15:35:10
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