My original post was here:
Thanks to all that helped me diagnose an intake manifold vacuum leak around cylinder number four on this 1997 Altima. After deciding it was too big a job for me to tackle (a man's gotta know his limitations), I took it to my neighborhood shop that I trust. He'd seen and fixed this before on Altimas, and told me he'd fix it and have it back to me by the end of the day. He did. It cost $475; $90 per hour x 5 hours, plus $15 for the gasket. I called a few other shops, and all wanted between $400 and $500 for the job.
It runs great now.
I also learned how to use an OBD II scanner, sort of, but not to rely completely on them. I just couldn't understand how cylinder four misfire didn't mean there was an electrical problem. I guess this depends on how and what the car's monitor/computer is set to recognize and report to the MIL.
Best of all, I learned how to test for a vacuum leak with carburetor cleaner...I didn't know that.
Speaking of carburetor cleaner, when I went to Autozone and asked for carb cleaner, I told the salesman what I needed it for. He gave me a can of engine starter and told me that worked better. I was skeptical, and read the label, which clearly stated not to use on a running engine and to keep away from hot surfaces and sparks. I declined, because I remembered something way back from when I was an eight year old boy living in semi-rural Maryland. The local church was having a pig barbeque. I got up at four am that morning to go watch them start the barbeque pit. The weather was cold and damp and misty, and the head honcho couln't get the fire in the pit started. You guessed it. He got a can of engine starter, stepped into the 8' x 4' pit, and sprayed about half of the can. He remained standing in the pit, bent over, and lit a match. Whoooooooooosh! The night light up, and he was literally thrown/blown out of the pit, and got all the exposed hair on his body singed (lucky he was nearly bald, or he'd have been on fire like Michael Jackson or Richard Pryor). No eyebrows, eyelashes, or hair left. Other than that, though, he survived. Guess he didn't know his limitations.
Bruce