89 Acclaim DTC 13,14 please help

Its never easy. 89 4 cly Acclaim. Helping a poor kid out with occassional stalling while driving around town issue. Got dtc 13 map sensor. He went out a bought it and I offerred to install it for him. Installed it and car was hard to start and kept stalling right out. Check engine light staying on. Reinstalled old one and now its doing the same thing. Checked voltage at the harness and getting 5V going to the map. Now getting codes 13 and 14(voltage at Map). Car runs poorly now and stalls all the time. Was running much better before I touched it. Kids only car and he needs it to get around and since I was the one working on it its sort of my problem now. Not sure where to go from here. Can't find anything on the net. Any help would be appreciated.

Dave

check the pcm connector for corrosion and inspect the ref return wire for damage it is 5v but if its shorted it may always read 5v rev the engine and see if the return voltage changes