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Old 08-05-2005, 12:41 PM
Mar10K Mar10K is offline
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Join Date: Aug 2005
Posts: 16
I put in the "old" MAF. Car ran fine for a few days. Yesterday, I got the rough idle again. I checked the codes, and show misfires on 4 of the 6 cylinders. I had read somewhere that if you unplug the MAF, the car will adjust, so I did that to see if the rough idle went away. Nope.

I happened to have the DTC code reader hooked up at the time, so I looked at the signals from the MAF. Here's what's odd - the inlet air temperature showed -70 (and 95 when the MAF was connected), which is what I expected. However, the air flow showed EXACTLY THE SAME, even changing with engine RPM, whether the MAF was connected or not!

I'm starting to wonder if I have a wiring problem. I plan to check the wiring with a voltmeter over the weeked to see if I have a short.

I also figured out what the MAF should read, based on this article
http://www.installuniversity.com/install_university/installu_articles/volumetric_efficiency/ve_computation_9.012000.htm

Based on 80% volumetric efficiency, I made this table:

Speed Estimated
rpm lb/min
0 0.0
1000 3.2
2000 6.5
3000 9.7
4000 13.0
5000 16.2
6000 19.4
7000 22.7

This will let me know if the numbers I see are reasonable.
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