cold weather problems?

[auto alchemist]

this is on a 93 thunderbird 5.0 HO


it seems like as soon as it got cold out ive been getting horrible mpg,i was getting 22mpg when it was warm and now that its cold im getting around 12

the car doesnt have any codes when i scan it, the scan tool sais its operating in closed loop, heres a list of things ive replaced so far

o2 sensors
coolant temp sensor
plugs
plug wires
distributor cap and rotor
coil
ignition module
air filter
maf sensor (used but made it run better)

after i replaced all these things i even reset the ecu bye pulling the fuse and still nothing. I havent scaned it again since i replaced those parts either though.

ive heard voltage drops can cause bad mpg, i havent checked the voltage yet but the meter on the guage cluster has always been on the very top notch in the normal range.

since it happened all of the sudden i figured it was a sensor, or something to do with a cold start system but idk anymore. It does seem to pick up a little mpg when it gets warmer than it normally has been.

im kinda stumped right now and dont want to dump a bunch of money on parts i dont need, does anyone have an idea of what might be wrong??

[facemelter71]

Mass air sensor could have something to do with it.Did you reuse your housing,or just the sensor itself?Mass air sensor directly controls fuel,and making it (run better) may also be hurting mileage.Let me know.?
Vacuum leak?
Does it smell rich,does it have cats.They might be clogged?

[auto alchemist]

i used the whole maf assembly including airbox lol it came off of my other tbird that doesnt have any problems.

i had to replace the maf because it would fall on its face everytime i would push the gas pedal past the half way point and it ran like crap, with the new maf it ran fine and i was getting 22 mpg with it on when it was warm.and all the rest of the things i replaced after it started getting bad mpg.

ive checked vacuum lines, and it doesnt seem to idle high, its an auto and it normally idles at about 8-9 hundred rpms once it kicks down off of high idle, i cant remember what it idled at when it was warm.

it does have cats so i cant tell if its running rich, but i do know there seems to be alot of water and moister coming out of the exhuast, it leaves oval shaped wet spots on the pavement behind it when its sitting still, i dont have any rotten egg smell going on so i dont think the cats are clogged.

i just figured it was a sensor because the mpg drop didnt gradually happen, and the only thing i did to the car right before it dropped was an oil change, and i actually used thiner oil (10-30 instead of 10-40 that was in it).

the weirdest part is the car runs just fine, it doesnt idle rough, there has been no performance loss or anything, and i cant find any fuel leaks at all either :confused:

[facemelter71]

Intake air temp sensor??
And the rotton egg smell people talk about,that actually means they are working.
Is the overdrive working.
well i guess it is since its a outside temp thing.
Ive had Ignition modules take a dump before,but before it let go,my car ran like it was 5/1 a/f ratio.It stunk.Tailpipes were beyond black.

[auto alchemist]

Intake air temp sensor??
And the rotton egg smell people talk about,that actually means they are working.
Is the overdrive working.
well i guess it is since its a outside temp thing.
Ive had Ignition modules take a dump before,but before it let go,my car ran like it was 5/1 a/f ratio.It stunk.Tailpipes were beyond black.

i was thinking about replacing the air temp sensor too, but i have a crappy haynes manual and the pic of it in the manual is from a v6 car, and there are 2 sensors threaded into the lower intake mani within a few inches of eachother that look exactly the same, are there two or just one?

if you could give me a pic of which one it is that would be great

[facemelter71]

I know on my car its on the drivers side lower in #5 intake runner.Might wanna check there.Its probly clogged up something nasty in there.

[auto alchemist]

I know on my car its on the drivers side lower in #5 intake runner.Might wanna check there.Its probly clogged up something nasty in there.

ok, thanks, i was gonna run some seafoam through it just because the car has 210K on it with the original motor, but i know im just gonna need to buy a new sensor.

im REALLY not looking forward to replacing it, i have a stock intake mani and it doesnt look like you can get to it with a wrench, any way i do it it looks like a PIA :(

[facemelter71]

Shit man its to bad.
Take the intake tube off and the intake bolts and prop that bad boy up with some wood.When i had my stock intake on there i didnt even unhook half of the crap that went to it.:bigthumb
And if anything breaks,you let me know,ive got plenty.

[auto alchemist]

i finally got around to doing it today, it wasnt as bad as i thought, swivel extensions and deep well sockets work wonders lol

i filled up my tank, now lets hope im finally getting better gas mileage, i dont want to have to park the thunderbird when i get the nissan done :(

[auto alchemist]

CRAP!!!

i got the intake air temp sensor in and its still getting HORRIBLE mpg, still around 12.

am i just gonna have to wait for it to get warm again or does any one else have some clue what it might be, i need help!!!!!