One problem related to gas recirculation valve (egr valve) has been reported for the 1998 Plymouth Neon. The most recently reported issues are listed below.
Had taken car back to carmax & they had chrylser dealership look & car found okay. 3/2001 had oil leak reparied by valve cover gasket, replaced oil cap, degrease engine, new oil, etc. . Months later. . . Leak worse & oil now in coolant. Told repair will be over $1000 and no guarantee of being fixed due to problem with way Neon's gaskets are made. Car must sit unused since "no sure fix for problem". You can fix it but will happen again due to how gaskets manufactured. . . Oil leaking all over road ways from these Neons can not be safe. . . Hazard, I do believe. Now can not drive car. Dt.