Need help. AFM voltage high?
10-21-2011, 09:16 PM
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Need help. AFM voltage high?
1992 400e 
I have had this issue for the past 6 months where I will be driving along on the freeway and my car will surge sometimes light and sometimes hard. The bad part is sometimes when driving for a bit (car is warmed up) I might get stuck in traffic and the car will die when I come to a stop. Now this happens very randomly and for the most part I drive 50+ miles a day with maybe one to two hiccups. The rest of the time the car drives great. Originally I thought it was a fuel issue and cleaned out my fuel system a few times. I eventually traced it to thinking it was my mass air sensor a few months ago and bought a new bosch unit. That did not fix the issue. I later replaced my spark plugs. I have also checked for vacuum leaks and tested out my coils. I replaced my wires and o2 sensor two years ago so I do not suspect them. Oh and I replaced my main harness a few years ago.
Now throughout this all I occasionally get code 10 "voltage at mass air sensor too high/low" that pops up on the diagnostic module. I just tested the LH-SFI and get code 4 which is "voltage at mass air sensor with hot wire. open or short circuit". Is this new Mass Air sensor bad? or could there be anything else that could be making me run this code?
I have had this issue for the past 6 months where I will be driving along on the freeway and my car will surge sometimes light and sometimes hard. The bad part is sometimes when driving for a bit (car is warmed up) I might get stuck in traffic and the car will die when I come to a stop. Now this happens very randomly and for the most part I drive 50+ miles a day with maybe one to two hiccups. The rest of the time the car drives great. Originally I thought it was a fuel issue and cleaned out my fuel system a few times. I eventually traced it to thinking it was my mass air sensor a few months ago and bought a new bosch unit. That did not fix the issue. I later replaced my spark plugs. I have also checked for vacuum leaks and tested out my coils. I replaced my wires and o2 sensor two years ago so I do not suspect them. Oh and I replaced my main harness a few years ago.
Now throughout this all I occasionally get code 10 "voltage at mass air sensor too high/low" that pops up on the diagnostic module. I just tested the LH-SFI and get code 4 which is "voltage at mass air sensor with hot wire. open or short circuit". Is this new Mass Air sensor bad? or could there be anything else that could be making me run this code?
Last edited by teamadidas; 10-21-2011 at 09:28 PM.
10-29-2011, 09:58 AM
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I fixed the issue the other day with a little help on another forum. I ended up swapping out the mass air sensor with another one I had laying around and the car runs great now. More power, no surging, and a smooth idle. Luckily my parts shop swapped out the sensor for me too with the warranty. The only reason I was ignoring the code for the mass air sensor before was because I figured the new one could not be bad. So my advice, don't always trust that a new sensor is still working properly. This is a bummer though as we always replace things assuming that we can rule them out afterwards.
