Sounds like the power transistor unit or the connectors associated with it, take a look at the front of the timing cover on the pass. side and take off the connector that leads to the little black box on the cover. Check it for corrosion and/or bent pins etc. This is very common problem, also, do a search for "power transistor unit" in the search function of this website. You ought to get used to trying to fix this type of small stuff with the Z, otherwise you'll be spending alot of unecessary cash...Good luck