ROUGH RUNNING 3

[Pat Cooke]

Hi from England,
Re: my 1990 ZR1.
Time to get it out of the garage and have another go at solving my rough running problem.
The symptoms are; starts up, runs smooth with normal power, as long as I keep the engine running it runs normally, if I stop the engine for more than 10 minutes it starts up running rough when hot, as if it is missing, power is down and fuel consumption up. I have replaced full set of coils which made no difference. Over the winter I purchased some Red Devil OBD1 diagnosis software for my laptop. Diagnostic trouble codes were 65 'oxygen sensor right side rich' and also 53 system voltage high,'battery voltage error' or 'EGR problem' or 'personal automotive security system (PASS-Key) circuit'. I purchased a new oxygen sensor which I thought I would put on the right side, having considered further I am wondering whether the right side sensor is detecting the rich mixture which is being caused by a faulty sensor on the left side or something to do with the code 53. Has the ECM got a limp home mode
Does anybody have any further thoughts ?
Regards
Pat