i have a 97 4.0 auto 4x4 and then ever its cold out side like under 40degrese out side, after its reached its norm temp the rpms will bounce from 500 to 1000 and some times die also wen slowing down like under ten mph the rpms will jump again and the whole truck will buck, and since its been gettin colder than hell it idles really rough at time while it warms up and its slugish when i first start driving and at idle if it does it will go from l050 rpm to 1100 the whole time and the truck will rock a little. i don't know whats wrong with it if its warm outside itll drive just fine with sum ***** i got no idea if anyone had this problem let me know so i can get it fixed . thank u
my codes are lean banks 1/2 and evap system low pres
things already done
sealed exzaust leak between o2 senss
changed iac
new plugs wires
sea foam
sparyed carb cleaner on upper to lower manifild with no rev up what so ever
looked for a fuse for my "o2 heater" but my truck does not and every fuse and relay is perfect
the maf and iat are clean

 

really people 92 views and nothing?

 

40 isn't cold.

There, happy I replied?

 

well the high today is 5 and thers 14in of snow on the ground

 

And? That's still not cold.

Are you glad someone's replying to your thread now?

 

no bcus im sure some one here knows whats wrong but they just dont care

 

One of the vacuum hoses is cracked. The best way to find out which one is to fill up the air box with water and run the engine.

CAUTION!!! DO NOT FILL IT UP TO WHERE THE FILTER IS IN WATER. I usually have done this on our work Rangers and filled it up until 1/4" away from the filter, but if it's your first time doing this, I'd go 1/2" below the filter.

When running the engine, you'll see steam/vapor coming from the crack. Don't take it to the shop and spend $80 on diags alone. Cheap and easy.

 

Check your speed sensor it controls fuel maps if the signal is inaccurate it can cause it to run too rich mine caused the codes and the stalling. Also the cold makes it worse.

 

hmm 2 winters ago i put on smaller back snow tires and have been using them since and my spedo will say 50 when im really only doin 45 on gps then 66 on the interstate to do 60 would that have anything to do with it?

 

Nah thats pretty standard for tire change that small a difference won't have much an effect on fuel. Mine was off terribly on the interstate the GPS would say 60 but the speedo would read 85 or 90. Scratch that idea. Could be the heater itself in the sensor thats bad time to break out the multimeter. Check the two black wires at the sensors they should read a few ohms resistance if it reads 0 or infinite resistance then the heater is bad and will not allow it to go into closed loop.

 

when they get around to plowing so i can move the truck ill look at that

 

I was also thinking vacumm line of some sorts.

 

Have you checked trans fluid level sometimes if its low the torque converter can act up and cause all sorts of codes. Sounds like the lean and low pressure codes may be piggybacking off each other.

 

the fluid is perfect its all royal purple only about 2 years old but the thing is it only does it when its cold it drives perfect when its above 30 like today i changed the iat 2 days ago and nothing changed im at the point that im now offering 200 cash for anyone to ******* figure it out i live in omaha and have family all over so i can send them the money and theyll give it to u because ill spend at least a grand at ford if its something small but if its big then a hell of alot more
thank you