Northstar Engines and System Technical Discussion Discussion, Engine revving on its own in Cadillac Engine Technical Discussion; I recently purchased an imaculate 1993 sts with the 4.6l from a little old lady that didn't want it anymore ...
I recently purchased an imaculate 1993 sts with the 4.6l from a little old lady that didn't want it anymore and I need help with it. When I bought is she said that one day she went out to start it would just idle up and up and she would have to turn it off. Well, when I got it home I started it and it fired up and it immediatly jumped to 2200 rpm and then every couple of second it would just keep climbing after about 10 or 15 seconds it jumped to about 5000 rpm and the headers started glowing because I'm guessing it was running lean so I quickly shut it down...any suggestions? It ran smooth while it was running and there are no codes in it except from trying to reset it by disconnecting the batt. Any help or suggestions would be greatly appreciated
I would look for a vacuum leak if I were you. Make sure that all the seals are doing their job, including the intake plenum cover (don't try to run the engine without it, it will run away unthrottled).
Fix all the vacuum leaks, then get back to us with an update.
I found 2 decent size cracks on the pass side of the intake. One of the cracks is a good 1/16 to 1/8 open so I'm sure thats enough of a vac leak for a couple engines. I found a place near me in MI to ship a good used intake with injectors and wires for $100. I guess I'll test the other injectors before putting it on, but other than that I think it should work.