sounds like a bad carb. the GM 2.4 had an issue with the tips on the spark plugs coming loose and cause a backfire which damaged the diaphragm in the carb. You can not get a diaphragm, only a complete carb. only way i know to test the trim valves is to use a scan tool and run them. should feel them clicking when it is running. any codes?
This is ONLY to be used to report flooding, spam, advertising and problematic (harassing, abusive or crude) posts.