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View Full Version : Chevy 454 high reviving at neutral throttle


Mahoney86
07-27-2012, 09:00 PM
Of course tonight we have epic conditions and trouble happens right as the first rider goes in. I replaced the starter today on my 93 Chevy 454. First rider goes in the water, boat ran great pulled him right up and after a few minutes he fell. I slowly went to neutral and the rpms started to slow until I was in dead neutral and the RPMs shot up to 2500-3000rpm. I immediately shut the engine up, pulled the rider in and waited a few minutes. Tried to start again and same problem. I checked all connections and everything seemed ok. Being in the middle of the river we needed to get back so started the boat, RPMs still high put it in gear and the RPMs slowed down and went to whatever throttle position I had it in. When back in neutral RPMS would shoot up. I sat at the dock for 30minutes or so looking over everything and tried to start it up again after playing with the vacuum pump that goes to the carb that controls the smaller set of butterflies. Everything worked fine, i took it for a quick spin and once I hit WOT with the throttle pinned and brought the engine back to neutral the problem started. If I didn't go WOT all ways fine.

Any clues? Obviously something is sticking, I am just not sure what. All the butterflies seems to move fine, I can't really seem to see anything sticking. What I did notice is there is a sensor that probably controls something with the vacuum pressure for the carb. There is a purple wire going to it which is connected, there is a short black wire with a male connector right behind it that has nothing to connect to. Could this be it? Maybe I knocked something when changing the starter?

Thanks in advance

Mahoney86
07-28-2012, 10:42 AM
No ideas? anymore information required?

thatsmrmastercraft
07-29-2012, 12:17 PM
You need to determine what if the throttle/linkage/cable is the culprit or if is in the carb. When it won't return to base idle in neutral, disconnect the throttle linkage from the carb and see what happens to idle speed.

Mahoney86
07-30-2012, 12:45 PM
It is not the throttle linkage, I see all of that moving to neutral position on the carb and on the transmission