I recently had some issues with lower MPG on my Monte. Thought I would share what I did in case it helps someone else.
When I first got my 2005 Monte LT 3.8 n/a @ 29K miles, I was getting 28 mpg on the 75 mile highway drive to work. At 100K miles it started slowly dropping off. Next thing I know I am getting 20 mpg on the same drive to work. Still ran great, but I figured it was time and did the plugs, wires, O2 and fuel filter. It didn’t help. I put on a fuel pressure gauge on it and base fuel (engine running vacuum hose off regular OR engine off key on) pressure was around 50 psi. In range but still low. I see that the regulator is adjustable so I turned the base up to 60 psi. Took it to work the next day and what do you know, back up to 28 mpg..
So if you have low gas mileage be sure to check you fuel pressure.

If you plan on adjusting the regulator, be careful it is a security torx and known to strip.

Doug

 

is this ok to do and , what should it be running at??????

 

Yes it is OK to do. It is about getting the pressure back to what it should be. Low pressure could also be a bad fuel pump, or clogged filter. However if that is the case adjusting the regulator will not increase the pressure.

KOEO = key on engine off
97 - 2000 VIN 1 & K KOEO 48-55 psi
97 - 2000 VIN 1 & K KOER 3-10 psi less than above

2001 - 2004 VIN 1 & K KOEO 53-59 psi
2001 - 2004 VIN 1 & K KOER 3-10 psi less than above

2005 VIN 1 KOEO 53-59 psi & 3-10 psi less running
2005 VIN K KOEO 48-54 psi & 3-10 psi less running

 

thanks ill check mine but i know i just redid the fuel filter about a month ag oor so ...my mileage isnt to bad but like 27 on hwy or so 20 around town so ithink im ok but thanks for that info

 

Thanks for the tip.. I'll have to check my pressure

 

can this be done with the 97 z i have been noticing these drops i used to get 30 on my 80 mile drive to the cape, now I'm getting around 22-25

 

Having the right fuel pressure is an issue with all fuel injected engines. I am not sure if a 97 has an adjustable fuel pressure regulator or not. Just look on top if there is a security torx then it is adjustable. Main thing it to just put a gauge on it a see where it is at..

 

I do want to add, before people jump on adjusting fuel pressure, general tune up stuff should be done first, change out all filters, depending on miles plugs,wires, I would include cleaning maf, and doing a seafoam treatment,

 

This is just part of checking that you have a healthy engine.
I should add that the injectors are spec'd to operate in a specific pressure range. Stay within the spec'd range.. Setting it to high, will not only have your engine running too rich, but will increase the load on the fuel pump and could possibly shorten its life.

What surprised me was changing it from the bottom of the range to the top made such a difference in the fuel economy. The car performs the same just increased my MPG