I've got a 91 Pickup 4cyl and the thing runs a super high fuel mixture, a high idol, and blows tons of white smoke from the tail pipe when first started.After it warms up a bit, the idol slows down, then speeds up and down again and up again, like the o2 sensor is not really sure what the fuel mix should be. After it is warmed up completely it runs like a dream. Anyone know why this is and if it something I should be overly concerned about? I used carb and choke cleaner on the intake to get some of the gummed up dirt out and lowered the idol screw down so when it is warm it runs smoothly. If I need to idol up and put some dirt back in there, let me know.

 

idol back up and when it is reving up and down like it does pull your tcase shifter back into 4wd if it stops or slows it verywell may be your tstat is bad and sticking if it doesnt change does it when you apply pressure to the brakes? vaccume leak somewhere if so