90 3.9 auto 2wd, When the weather gets below 50 or so, my truck has started running like crap. won't idle, won't go over 40mph, and it seems to be getting worse. I tried running a can of seafoam thru tank of gas thinking maybe it was moisture but doesn't seem to be helping. Today I changed fuel filter and I'll see how that helps tonight when I leave for work. Any suggestions yall can think of?

 

It could be a bad Coolant sensor.

 

Bad catalytic converter?

 

+1

Had pretty much the same problem on my '86 LTD/Crown Vic with a 302

Stumbled at idle, 1/4 throttle, surging idle, replaced the sensor, and were good.

Also maybe vaccum lines????


George

 

my truck gets like that when the weather starts getting cold...i put heet in the gas tank and its good for the rest of the winter.

 

Have you checked codes? Key - ON - OFF - ON - OFF - ON without cranking or starting & count your check engine light flashes.