I started driving my car more often lately after having it stored away. The fuel economy has been in the 19 mpg range. It should be better than that right? I dont have any crazy gas guzzling mods. I have been running the 3.8 size pulley and not the 3.4. I have headers, the GM Tuners tune, SC2 injectors on a SC3 rail, and the ZZP SC3 to Northstar throttle and MAF. I should be getting better mileage than 19 mpg right?

Could be the program in your PCM is it all done to match the throttle body and MAF you are using.

I'm getting around 16 - 19 in town depending how heavy my foot gets and 27 - 29 on the hwy.

MT transmission?

quote Originally posted by boostme: I started driving my car more often lately after having it stored away. The fuel economy has been in the 19 mpg range. It should be better than that right? I dont have any crazy gas guzzling mods. I have been running the 3.8 size pulley and not the 3.4. I have headers, the GM Tuners tune, SC2 injectors on a SC3 rail, and the ZZP SC3 to Northstar throttle and MAF. I should be getting better mileage than 19 mpg right?

Sounds like ur tune needs some tuning. Is all ur driving in town?

This may not be the answer that you are looking for but the first step is to do a complete and total scan. Not with those $150 scan tools but with a laptop program like HP Tuners that maps the fueling relative to all engine operating parameters and conditions. It will also tell you if a sensor is not working properly or if a sensor input is defective/missing. Once you have that data in hand you can move on to solving the problem.

BTW if you changed MAF sensors, the table for that new MAF must be imported into your program. The response curves of different MAFs are all different.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Powerlog manifold, Northstar TB, LS1 MAF, 3" Flotech Afterburner Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

[This message has been edited by Dennis LaGrua (edited 02-10-2014).]

Friend of mine had a Pontiac Grand Prix 3800SC last year and the best mileage he ever got was 19

no matter how right or wrong the "tune" is... you are going to have your narrowband o2 sensor making changes based on what it sees.... If you have an exhaust leak introducing air into the o2 sensor then you are going to have the PCM thinking the engine is running lean, and it will add fuel.

I have the getrag 282. I drive a mix of in town and highway. The highway would be a 30 miles cruise most of the time. I will look for exhaust leaks and contact GM Tuners about my tune.

I see 14.3-15.7 on the wideband most of the time. I never have a chance to watch it when I go full throttle, too risky.

[This message has been edited by boostme (edited 02-10-2014).]