Can anyone assist me ? I have an 02 s80 that has developed a hesitation or slight surge during ecceleration at 40 and 60 miles per hour. I have replaced the fuel filter ( the old one was very dirty, I captured the fuel and it was black) I have also put Sea Foam in the tank and driven 200 miles with no change in symptons. I checked the fuel after installing the new fuel filter and it is clean. I have less than 5000 miles on the spark plugs and no check engine light. the car has 206000 miles on it and it is a non turbo engine. I would appreciate any input in helping me solve this issue.

 

I sometimes have some slight hesitation on acceleration with the RPM is around 1300-1700. Very slight,like it wants not to shift up or accelerate at a higher RPM so to speak. I've heard that there is a software upgrade the improves shift performance with the transmission.

 

Thanks, is this a dealer software upgrade?

 

I do believe it is a soft/hard upgrade.