graysonZ

Hey guys, thanks for taking the time to help me on this issue. I looked at a lot of posts and I just need some general guidance not sure where to start. So I'll tell you the story what happened... My 1975 280z has been running great since I bought it about 2 years ago. Drive it pretty much every week at least a couple of days or more. Changed the spark plugs about 4 months ago which helped the performance a little bit and a k&n filter. That is probably the only thing that is aftermarket on the engine. It all happened after I changed the thermostat. It wasn't letting the coolant in so I replaced that. Probably was overdue. For a couple weeks of driving it would idle kind of rough in the morning and then when it warmed up it drove great. Then some times if I got on it a little bit it would cut out and act like I was letting up completely on the gas. It stalled on me at a light after I slowed down on one of those. Then for a couple weeks or so it ran perfect. I then had my friend do a little body work and he drove it around a little bit. He actually put 91 in it when I always use 87. When I picked it up and drove it home I couldn't even go a mile. Idled really bad and stalled. I had to tow it to get it home. I since changed the fuel filter and put new gas and fuel injector cleaner in it. Ran a little better but still cuts out. Once I turn it off it's hard to get started again. Black soot on the tailpipe and on spark plugs. Any suggestions or what kind of mechanic i should go to would be great. Thanks, Grayson