Originally Posted by ViperRTBlck
i just recently bought a 95' SSEi bonneville thats been sitting for 6 months in storage...it just turned 94000 miles on it---some things dont work but everything is starting to coem together and work again...but the gas milage is TERRIBLE---i've heard and read that these engines (3.8 supercharged) get about 20 mpg....so i calculated it--this car has an 18 gallon tank...i have 1/4 tank left and almost have 200 miles to this tank...so im getting about 12 mpg...this is TERRIBLE....what'* wrong?...also just today it periodically started this----longer than normal starts...one of my buddies said something about a pressure regulator---he said turn the key to ON....then turn it off....and then start the car up---i did this---and he was right---it fixed the problem...meaning that the problem was this valve or w/e....if anybody knows where this valve is at or anything else about my problem...PLEASE help me...also--when in gear...it does idle a bit low(it vibrates a small bit like any car does when it'd idling too low--give it a tad bit of gas and it smooths out)...this is just my thought from a quick thinking--plugs and/or wires could use a change and possibly at the same time help my fuel milage....but then i also thought--well i could have bad injector(*)....this could possibly cause the longer than normal start too maybe---from leaking or something----but anyways im looking for help because this fuel milage thing is really upsetting--if anybody has any advice or knows anything or has experienced the same issue---please let me know and help me out...
Firstly, congrats on that car and welcome to the forums!!!!
Now, the second most common cause of bad gas mileage (Next to a 2 ton foot on the gas pedal) is your O2 Sensor. If you peer over the back of your engine, down towards the bottom, you'll see a connector that sorta looks like a big spark plug with a wire running out of it that is plugged into the exhaust. That'* your O2 sensor. When I picked up my 94 at around the same miles you had now, I was getting @#$@# mileage too. I changed that sensor and all is great.
BTW, if you could go into your profile and set up your signature with your Year and trim level as well as any mods you may have made to your car up to this point, it'll help the uber gearheads in the forum give you the best advice quickly.
Once again, welcome to the forum!