Re: slow engine
Hey BlueBronco, just so we understand this right... In Park, your foot's to the floor, tach reads only 4000 RPM, and parts aren't flying through the hood?
Is it running smooth at this RPM or missing bad?
If it's running pretty smooth, and really is at only 4000 RPM at W.O.T. unloaded, I would probably check Fuel Pressure at the test port, to see if it's low. If it was, then the EEC may be maxing out on Injector "ON" duration, but still can't get enough fuel in to get to higher RPM. (I have a test gauge, so it tends to bias my troubleshooting towards using it early, and eliminating fuel delivery as a problem). You don't have any kind of restriction in the intake path, do you? Like when engine is OFF, foot to the floor, is the throttle plate wide open? No really grungy Air Filter?
If you think that maybe your tach is wrong, tell us what Diff ratio you have, and what size tires, and go 60 MPH in 3rd gear (lockout OD) and tell us what RPM you see. There are plenty of Bronc folks on this board that we can match equipment and see if your tach's measured RPM is in the ballpark.