4.3L will not idle

[JustChilling]

I have a 4.3L GM in a 1986 wellcraft. I cannot get it to idle everytime I get to about 900rpm it ends up stalling out. I have pulled the throttle linkage off and it acts really strange when I open the throttle it runs up just fine and when I close the throttle it does not back down right away. It seems to slow down in stages. It has a 2-barrel merc carb. opened up the carb and was surprised how clean it was inside no trash or water inside.Last time out ran fine for about 30 minutes then started bogging down it ran fine at about 2500 rpm but brought it back to the dockto check out. I have put new plugs,cap,rotor,pickup sensor hoping this would take care of it but now cannot get it to idle. Engine sounds really good with the throttle open a little but will have a really tough time in a no wake zone. any suggestions would be greatly appreciated.

 

[Don S]

Re: 4.3L will not idle

When was the last time it had a complete tuneup?<br />Cap, rotor, sparkplugs, Compression Test timing check, advance timing check, adjust carb mixture, and carb idle speed. The fuel filters also need checked for water and junk.

 

[JustChilling]

Re: 4.3L will not idle

thanks don, I have installed new cap,rotor plugs, fuel/water seperator and screen on carb(clean no trash found)I got to get the idle down to check timing.I have moved dist. trying to get idle down and carb idle. will try idle mixture screw and compression test. Thanks for the info on the compression test will check that also. I really do not understand why it will not back down right away when I close the throttle. backs down to about 1500rpm then slowly to 900 then starts to stall.

 

[lowshovel1]

Re: 4.3L will not idle

No points in yor tune-up?or is it electronic ignition?

 

[Don S]

Re: 4.3L will not idle

Disconnect the throttle cable from the carb and see if it will return to idle. The cable may just be out of adjustment.<br /><br />lowshovel, he has electronic ignition .... Thunderbolt IV.

 

[JustChilling]

Re: 4.3L will not idle

electronic ignition replaced pickup just because screw broke the stud off dissasembling. this is happening with and without throttle cable.going to go out and try idle mixture screw when the sun goes down. Forgot to mention before this all happen the exhaust boot blew and sprayed water all over the engine while running. checked temp gauge right away did not run hot boot was just dry rotted.

 

[JustChilling]

Re: 4.3L will not idle

starting to get frustrated now I went out to do a compression test pulled #6 first plug was fuel fouled probably need a wire set went to 160psi next went to 4 plug had water on it turned engine over just a little shot out compression good @200.plug 3 same thing little water good compression. went to other side plug 3 water again!! good compression 200. this water thing is really getting me nervousso I had to leave it for a little bit. I just put new riser gaskets not long ago but did not use any sealant could this be the problem hopefully or am I just wishfull thinking. exhaust boot blew 2 trips ago so water should not be from that

 

[waterone1@aol.com]

Re: 4.3L will not idle

Ok, first we need to be clear on what you are calling an exhaust boot? Since you said it sprayed water all over the engine, are you talking about the rubber coupler that goes from the exhaust riser to the Y pipe ? If so, I will do the math here.... exhaust coupler blows + sluggish performance + water in cylinders = exhaust restriction in Y pipe....most likely stuck shutters....just my guess

 

[JustChilling]

Re: 4.3L will not idle

yup the rubber coupler, butit was a restriction in the riser. Not running hot at all now. Last time out (after replacing coupler and shutters free) the boat ran fine for over 30 minute before problem started. That is why when I got back I tried cap, rotor and plugs. Good guess though I like how you figure step by step thanx.