Subject	Re: Loss of power, rough idle
Posted by	Seyr on January 07, 2011 at 6:05 PM
	This message has been viewed 107 times.
In Reply To	Loss of power, rough idle posted by Seyr on January 04, 2011 at 08:54 PM
Message	I got the following codes: 51: Injector Circuit 12: Air Flow Meter Circuit 34: Detonation Sensor Circuit I tested the MAS first because of something I read in the factory service manual (page EF&EC-34): "Air Flow Meter Malfunction If the air flow meter output voltage is above or below the specified value, the ECU senses an air flow meter malfunction. In case of a malfunction, the throttle sensor substitutes for the air flow meter. Although the air flow meter is malfunctioning, it is possible to start the engine and drive the vehicle. But engine speed will not rise more than 2400 rpm in order to inform the driver of fail-safe system operation while driving." This matches up exactly with what I was experiencing on the road. The engine wouldn't go past about 2400 rpm. So I figured it was a good place to start. I didn't conclude anything definitive however. The diagnostic procedure for the MAS is on page EF&EC-111. 1) Ignition switch on. Test voltage between pin E (#4pin) and ground. Result: Battery voltage; Pass. 2) Ignition switch on. Test voltage between pin B (#1pin) and ground. Expected: 0.8V. I only got 0.37V; Fail? 3) Engine on. Test voltage between pin B (#1 pin) and ground. Expected: 0.8V-1.5V. I got 1.5V; Pass. 4) Ignition switch on. Test continuity between pin B (#1 pin) and ECU terminal #27. Pass. 5) Ignition switch on. Test continuity between pin C (#2 pin) and ground. Pass. Basically, the harness/connector all checked out except for low input signal without the engine on (test 2). I don't know whether that matters. The factory manual says to inspect the MAS hot wire for damage or dust. I can't visually see anything wrong with it. What are the odds that my problem is due to a faulty MAS that should be replaced? Are they known to fail? Keep in mind that my MAS is still working to some extent e.g. blowing into it with the unit removed from the intake will lower the engine speed. As far as my other codes go, I'll take another look at the injectors. If I understand correctly, the detonation sensor isn't something I can easily get to anyways. Thanks for any input you can provide!
Follow Ups	Loss of power, rough idle - Seyr 20:54:28 01/04/11 Do have any codes? - 300zx_2+2 21:43:55 01/04/11 Re: Do have any codes? - Seyr 00:12:59 01/05/11 Could be as simple as a large vacuum leak. Check - doug8867 07:44:42 01/06/11 Re: Loss of power, rough idle - Seyr 18:05:35 01/07/11 you could replace it and have it work. when mine did that... - 300zx_2+2 20:28:13 01/07/11
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