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Old 07-08-2010, 02:38 PM   #1 (permalink)
eco....something or other
 
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running lean, code 172, and vacuum leak

The vacuum leak is in the back of the EGR valve. The valve stem is leaking on the fresh air side. Is this why my mileage is so good? If I replace the EGR valve will my mileage go down? I don't think it is dangerously lean, just enough so the 02 sensor doesn't switch a lot. I remember a thread a while back about unmetered air...guess now I get to experiment.

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Old 07-08-2010, 02:58 PM   #2 (permalink)
eco....something or other
 
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never mind the replacement.....$90! I am not going to be buying a replacement.
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Old 07-08-2010, 03:55 PM   #3 (permalink)
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electrical tape?
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Old 07-08-2010, 10:22 PM   #4 (permalink)
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I'm the Unmettered Air Leak Guy

I eventually got a Wideband and it showed the AFR was still 14.7:1, so it was determined that the PCM believed the engine was running at a lower load that it actually was and therefore was advancing the ignition timing a little. You may be expieriencing the saming thing...
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Old 07-09-2010, 12:26 AM   #5 (permalink)
eco....something or other
 
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So this is good? I might want to turn my timing back to 10-12 instead of 14?
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Old 07-09-2010, 10:59 PM   #6 (permalink)
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I'd just leave it the same if it's working and you don't detect any issues. You'd only be changing the base timing by moving the distributor, I don't believe it will help by moving the base timing back, you might want to play with the base timing to see it's effect on mpg's....
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Old 07-10-2010, 12:24 AM   #7 (permalink)
eco....something or other
 
Join Date: Jul 2009
Location: Colfax, WI
Posts: 717

wood hauler - '91 Ford F-250
Team Pontiac
90 day: 18.97 mpg (US)

Rav - '06 Toyota Rav4 Base
90 day: 26.52 mpg (US)
Thanks: 39
Thanked 60 Times in 45 Posts
I moved it from 10 to 14 a while back to increase low end torque but I did other mods at the same time so it is hard to tell what I accomplished mpg wise with the timing. I will try turning it back a little and see what happens.

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