avanel

hi I have a 99 ek3 civic that I bought from someone. When I drive it, I find that the transition from 1st gear into 2nd gear is a bit loud but not smooth and sometime whilst driving, the car holds back. I thought that it would cut off but it didn't. It kept driving. I had the injectors cleaned, had a general service done on it, changed plugs, oil and filter just before Christmas last year and I changed my oil to Castrol 20/50 which works great. It worked great for a while but I find that I am having a similar experience again. my heat gauge keep going right up but the engine does not overheat. help please!