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1997 Metro MPG...; 26-27 MPG?
Topic Started: Mar 6 2009, 06:22 PM (5,226 Views)
Manny
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Yes! a Costa Rican member

Yeah! warm up...

I personally don't like to run the car just after cranked and turned on,

So of course based on my location warm up time is quite less than yours... :P

Will see if mileage change after new pump
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Bad Bent
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Facetious Educated Donkey

Oops, Being facetious. :smackface
You are so correct about warm-up. I went the extreme and added an in-line coolant heater. Our high today was in the high 20's. I'm happy because water stops moving below 32F and I'm still moving. :D
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fainya
Fainya
[ *  *  *  * ]
When you did the compression test, Was the engine warm? Did you have all the spark plugs removed? Did you have the throttle set wide open? Is your battery and starter in good shape? If you answer no to any of the above questions you will show lower compression.
How old is the timing belt? If it is streached, compression will show low.
As for a shot fuel pump, have you tested your fuel pressure with a guage on the inlet side? what pressures did you see? What did the pressure climb to when you squeezed off the return hose?
Have you changing the fuel filter before running these fuel tests?
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mwebb
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FOG

low compression will cause poor fuel economy - IF it results in misfire and incomplete combustion .
what are the fuel trim values on the car ?
sum of all fuel trims must be within +/- 10% of zero fuel trim adjustment at cruise and idle and 2k rpm .
+/- 5% is better
a 1997 system will have fuel trim values in scan data even generic OBD2 scan data will function.

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if you do not have access to a graphing or logging scan tool , record LongTermFuelTrim value at idle and 2k rpm while observing the scan data -
this is not as accurate. see Short Term Fuel trim above at +20% , then look at rear 02 sensor voltage , over 1 volt , front 02 sensor voltage , under 500milli-volts , MR ECM as adding fuel because the OIL SOAKED and very fraked front 02 sensor is telling MR ECM that the system is lean , so MR ECM adds fuel until it sees the Front 02 sensor value increase , which it can not because the front 02 sensor is fraked .
the rear 02 sensor is telling the truth
the system is rich as a bitch .
MR ECM is commanding to add as much fuel as it can based on the authority of the defective fraked front 02 sensor
this one is not going to be getting 50 mpg as it is now .
........................................................
with many scan tools;
you can log fuel trim values while driving the car and see what they are - if they are NOT within values above especially if Fuel trim values are subtracting
you need to find out why
IF fuel trim values are "good" as per a captured recorded log - then
...................................................................................................
will a failing fuel pump cause poor fuel mileage , maybe -
if the pump is exhibiting cavitation .
the vapor "bubbles" can accumulate at one end of the fuel rail causing injectors on that end to starve for fuel which may lower overall engine efficiency and therefore lower fuel mileage ...
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but that scenario does not happen very often in the real world -

now
let us speak about restricted EGR flow .
that is more common than anyone may imagine and it will for sure reduce fuel economy .
and fuel trim values will be "good" even though EGR flow is "bad".
and
fuel mileage will be "bad"
Edited by mwebb, Jun 9 2009, 09:37 PM.
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