I just bought a 01 S type, on the ride home I noticed a slight bumping in the transmission like it couldn’t make up its mind on what gear it wanted to shift into! But I hade just filled it up with cheap gas and I saw in the owners manual that your supposee to put premium only, so I let it go almost empty thin filled it with premium. It seamed to fix the problem, but today it did it ah couple of times, it dos it at about 55-65 mph and about 2000 rpm. Do you guys think it could be the gas or maybe something ells????

 

So do you think I should try changing the spark plugs? If so what kind do you recommend? I haven’t looked at them yet….Or do you think It could just be that cheap gas getting out of the system? Thanks so much for the info!