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Old 12-28-2012, 02:16 PM   #1 (permalink)
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Scootahbugguh - '94 Geo Metro XFI
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Head gasket replaced/head reconditioned = loss of 4 to 5 mpg (10%)

I recently had my 1994 Geo Metro XFi serviced due to lack of power. The head gasket was replaced and the head was reconditioned. Now I get 41-42 mpg and before I would get 45 - 47 mpg. Nothing else has changed. When I was told I was told that the previous owner had the car tuned for gas mileage. Given the work that was done what else besides engine timing would have been tuned? I was hoping the head work would result in more mph not less.

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Old 12-28-2012, 04:21 PM   #2 (permalink)
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Well one idea I would try is check or replace the O2 sensor , sometimes the gasket materials or glue can affect it . plus of course all the other usual things, plug gap , timing etc, if it's just the first few tanks it may even out also maybe they put in thicker oil when they changed it, hope they changed t.
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Old 12-28-2012, 04:23 PM   #3 (permalink)
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Yes they changed it but I have no idea what oil they put in it. Thanks for the suggestions.
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Old 12-28-2012, 09:44 PM   #4 (permalink)
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Sounds like they changed the ignition and maybe cam timing on you.
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Old 12-29-2012, 08:54 AM   #5 (permalink)
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Looking at you fuel log last Dec show you right around 44 mpg, remember cold weather reduces mileage. Also looks like your car was seldom used for 3month? Don't forget to check the tire pressure if you haven't or you could have a brake dragging.
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Old 12-29-2012, 12:11 PM   #6 (permalink)
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Scootahbugguh - '94 Geo Metro XFI
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Quote:
Originally Posted by nemo View Post
Looking at you fuel log last Dec show you right around 44 mpg, remember cold weather reduces mileage. Also looks like your car was seldom used for 3month? Don't forget to check the tire pressure if you haven't or you could have a brake dragging.
The time it was seldom used is when it was in the shop getting fixed. They took FOREVER to fix it. If I had known is was only a head gasket I would have done it myself. Is there a thread somewhere that lists the fuel economy tweaks for a metro XFi? I can advance the timing at the distributor if it's as simple as that.
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Old 12-29-2012, 03:24 PM   #7 (permalink)
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I would double check that the cam timing is correct.
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Old 12-29-2012, 04:54 PM   #8 (permalink)
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You mentioned that the head had been reworked as well... Along with the timing (both cam and ignition) if the head was cleaned, depending on how much carbon was cleaned out, you may have increased the displacement back to near factory, would would require more fuel to keep the correct a/f ratio.

Also, if the head were shaved true it could cause the cam timing to be slightly off, since the effective length of the belt/chain will be slightly increased.
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Old 12-29-2012, 04:59 PM   #9 (permalink)
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I thought slightly retarded cam timing would improve low rpm torque, but hurt higher rpm power, i seem to remember back in the seventies they did that to almost all ford v 8's to help emissions . I could be wrong on this one,
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Old 12-29-2012, 05:00 PM   #10 (permalink)
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you have it backwards.... retarding the cam helps out high RPM at the cost of low RPM.

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