Got off the freeway after a long drive and as I was going over the overpass the engine just stalled. I pulled over and the engine was actually still running, but incredibly slow and the RPMs were not high enough to register on the tach, it was just sputtering and then stalled and won't restart. The injectors are firing during crank but the engine won't fire. Backfired once incredibly loud while I was trying to crank it over, not sure if this is evidence of spark or not. I have very limited tools and I'm trying to troubleshoot, over 70 miles from home. Opinions?