I have a 1999 ford ranger automatic 120k that starts to shift hard from first to second and sometimes drops from second to first for the first five or so miles then smooths out "sometimes". It progressively gets worse until i unplug the terminal and reset the computer. This technique works for about two weeks then starts all over again. I have replaced all the external sensors and still same problem. Brought it to a tranny shop and they cannot find the issue. Any suggestions?

 

Have you had the codes read?

 

yes, no codes

 

Problem solved, the truck went through three transmissions and had pre-ignition problems. After several sensors replaced, there was only one left was about to give up. It was the maf, fixed every single problem i had. Never threw a code.