My 1993 Isuzu pickup with a 2.3L 4 cylinder has started to stall when I take my foot off the accelerator, it runs fine as long as I am giving it gas, but when I take my foot off the gas to stop at a light, it dies. It always starts right back up. Recently, it also stalls when I crank it unless I am giving it gas. It seemed like vacuum but the shop did a smoke test and could not find anything. Finally I cranked up the idle adjustment so that it idles around 2k RPM. So far so good, but obviously not the right answer.