About a year ago, while enroute to San Antonio from Arlington, when I stopped for gas and started out again, I noticed what I first thought was simply a 'miss' in the #4 cylinder. Didn't think too much about it until a couple of weeks ago. Changed the plugs, adjusted/cleaned the points (both sets), thinking that was the problem. Nope. Check with my favorite Volvo mechanic in Fort Worth, found out the injector isn't firing. Can someone tell me how to find the source of the problem, i.e., tracing the wire, or how to measure the impulses? I really don't have the bucks to buy another set of injectors, much less just one. And can I remove the one injector and repair it?