A fuel injected engine, when shut off, gets both, spark and fuel shut off, a carbureted engine only gets the spark shut off.
Excellent statement-never seen it published before.
Speed more than anything, bring any older car up to 1000 rpm on a hot day and cut the switch without letting up on the gas and watch it trash like a headless chicken.
But now a days with unleaded gas you can almost wipe the little bit of carbon off of a 100,000 mile old engine's piston top with toilet paper. Its amazing how much of the old "carbon" (which literally had to be wire brushed or scraped off the pistons) was due to the lead in the old gasoline. Lead's residue was left all the way from the "carboned-up" combustion chambers and spark plug deposits to the light gray tailpipe condition seen after an extended highway trip. Years ago this was considered pure b.s but now everyone can see the proof.
