ive got a 1991 Dodge Grand Caravan. she's been a great winter beater for me, and a great car for my family, mainly my mom prior to that. shes got 209k on her. anyway. i'll fast forward to the part of the story where my issue's begin.

so i am cruising down I-94, got my cruise set at the usual 71 mph. at this point i am usually getting give or take 25 mpg. i had been on the road for about an hour, when i happened to look up at my computer (which in mine has been dead accurate) and the instant economy guage read 18 when i was going DOWNhill. i found this odd, but not as odd as when it dipped to 9 on the climb out of this valley. i thought maybe the injector got a pinhole rusted in it again. (when we first got it at 128k in fall of 2002, it had **** poor fuel economy and i always smelled gas, but never any puddles. after bout a week i discovered a pool of gas on the valve cover. put a new one in, direct from the factory, which i believe had new injectors included. i am checking with my buddy in parts tomorrow)
but when we stopped in kenosha for gas, i checked this, and ruled it out. however the exhaust was RICH. i mean you start welling up at stoplights and your throat and lungs feel like there there on fire kinda rich. as in Al Gore would probly try to shoot me dead if he saw/smelled me driving it. but he hasn't. so ha. and its not me being a pansie, i own a few nice pre emisions (some post emissions... passing was 120 grams of CO per mile, and she was throwing 150, AFTER we retarded the timing and disabled the vaccuum secondaries....) pieces of iron, and it beats them. my thoughts are 1 stuck open injector, or a bad seal on fuel pressure regulator, causing the vacuum line to suck gas in that way, or possibly a O2 sensor on the fritz (though i hate to even list that as people always go "replace the o2 sensor" even though there fine, or what caused them to fail goes undiagnosed.
i'm not a fan of "mechanic in a bottle" remedies, but i did dump in a bottle of STP's injector cleaner (at a $1.84 a bottle, i figured what the hell) to a 1/4 tank of gas, and my problems seemed to go away, but alas, they have returned 1 tank later, and i continued to run another bottle through on a full tank, my mileage avg was about 19 for on the freeway. a hair better than what it was. but not 25-26.

any help on this would be appreciated. just to possibly save me some time before i bust out my multi meter and start doing tests galore.

thanks in advance

Jake

 

Start out by getting any fault codes read.
This can at least point you in the right direction before the $$$$ start flowing.