I took my 2002 grandprix gt into a local repair shop to have it looked over. To my surprise, they found alot more wrong than I imagined. They have replaced the intake manifiold gaskets, plugs, plug wires, both axles, an upper control arm bushing, both radiator hoses, both upper motor mounts, serpentine belt, and all four tires. after picking my car up (it was after the shop had closed) I test drove it on the highway. NOW the problem is that when I get it over 50 MPH and let off the gas pedal, the tachometer and speedometer fluctuate wildly followed by the transmission downshifting out of overdrive. I took it back the next morning. Well, after they had it another whole day ( a total of three days now including the original repairs) they can't seem to find the problem. I am hoping to gain any insight on a cause/fix so I can pass it along to them and get my beloved car back!! BTW, the tach/speedometer problem showed up only AFTER thier repairs.
