Hiccups - Game for Engine Experts
I need some serious help here. I am about to hand this over to a shop but fear the 11 hours they could take to just find the problem let alone fix it...at $100/hour.
When the transmission is engaged, forward or reverse, there are significant hiccups that have a similar feel as a cylinder missing or the prop thumping into a piece of soft wood. In other words, a slight and very brief reduction in forward momentum with a shake occuring every 2-5 seconds. This happens from 850rpm to 1500rpm, from there on up it stops. Although throttle respons isn't as good as it used to be. Additionally, when coming off plane the engine can die, and at times have a back pressure pop. A discomforting situation I don't want my wife in while driving me skiing. This occurs in the water, or on dry land with a wetted drive shaft. On dry land I have also applied some resistance to the coupler to simulate some resistance that would occur in water, with my boot.
Strange part: Engine runs perfect in neutral and when the transmission is disengaged. It revs great and at worse it only needs two pumps of the throttle and fires right up.
Facts & Conditions
-1993 PS 190 with Ford Indmar engine; BorgWarner Velvet Drive 1:1
-Original Holley carb, has not been rebuilt in the 4.5 years I’ve had the boat
-Issues began after I put on new GT40P Heads, and after shipping from CA to OH
-Heads & rockers torqued to proper specs
-Can still hear the springs popping after running engine as they break in
-New spark plugs – wired in proper firing order
-FantasticFinishMarine.com a ski boat tranny shop in Medina OH says my problem is not the tranny. As much as they’d like it to be so they can sell me a new/rebuilt tranny.
-Pumped and replaced tranny fluid
-Cleaned every connection that deals directly with the engine
-Can’t exactly source the origin of the sound/hiccup since it shudders the whole driveline
-I've played with adjusting timing and believe it's dang near as good as it gets but could be wrong
-New MSD Coil - fleeting hope it was the cause
-With higher performance heads do I need a performance intake manifold? Easy to replace
-Could my tranny be going south? Easy to replace
-Could I have an issue with the pressure release valve on the tranny?
-Could I have one valve giving me issues with, possibly one spring that’s a little to taught or too soft?
-I do still need to replace the fuel water seperator.
I will take some video of the condition and post up soon to lend more clarity to the explanation - at least from the driveway, maybe from the lake.
Maybe I'll offer a prize like a whole bunch of ZonePerfect nutrition bars, Stabucks or gas card to the genious that can help solve this gremlin problem.
Last edited by Ryan; 07-29-2008 at 11:44 PM.
|engine trouble, gt40, hiccups, ryan, transmission|