91 Voyager

My 91 Voyager has recently been chugging back the gas and when it has warmed up and travelling at a constant speed, it looses power and begins to chug. I have to floor it to get it to run smooth again. This has quite frequently. Any ideas as to the problem..

Thanks

Try doing a complete tune-up as well as cleaning out the throttle body. My Wife's did the same thing and ran fine after the cleaning and tune-up.