86 sunsport - high idle

[awesomesteven]

Ok, I got everything running nice but i'm idling at about 1700. I have my air/fuel mixture screws 1 and 1/2 turn out but I have my fast idle screw turned so that it's idling that high. If I turn it back it just dies.

I don't know if this helps but I sprayed some carb cleaner around the carb base and intake manifold and there was no change in the idle speed. The timing is right at 13 degrees and if I try to back it up to 10 it dies out on me too.

Carbs are just one of those things I'm not great at diagnosing so I wanted to see if you guys could help me out before I ask a pro to come help me out.

[chris young]

By the sounds of it, either your idle circuit is plugged or it's flooding at idle. (gas dripping from the primary boosters while it's idling and probably a minute or two after shut down) I only say this because it was happening to me and when I did a quick search I found it was fairly common. I'm assuming you've got the Holley 4160 on your boat, and if you do it is pretty much guaranteed to have the nitrophyl floats, and apparently they start to sink after a while. I set mine correctly and put in a new needle and seat and it still flooded. Last weekend I adjusted the float a bit and it seemed to correct the problem. I've ordered a new set but have yet to get them into the boat. The Holley P/N is 216-43

I keep posting this, and will continue to do so. All those who work on engines should have a decent vacuum gauge and know how to use it. They're not expensive, but you can learn so much about the health of your motor in so little time.

There are tonnes of sites out there that will guide you through using a vacuum gauge but they all say basically the same thing.

http://www.secondchancegarage.com/public/186.cfm

[awesomesteven]

Thanks for the link, I'll have to invest in a vacuum gauge sometime soon.

I can rule out the flooding issue. I did have the issue earlier in the summer but I adjusted the floats. I do have the 4160 and I have to say that it's a shame we have to pull the float bowls out in order to adjust.

So from your suggestion it would leave me with the idle circuit being plugged. I cleaned the crap out of this myself about 2 months ago and then had a pro clean it and rebuild it for me since I didn't get it right the first time. Could it have gotten plugged already? I guess I could spray some carb cleaner so see if that works.

[Moor]

Steve, do ou have this problem all the time or just for the first few minutes or running? is your choke hooked up and fuctioning properly? Still sounds like a gummy idle circut though.... id defintaley invest in a vaccume gauge, your engine will thank you in the long run

[awesomesteven]

is your choke hooked up and fuctioning properly?

You know what? I forgot all about the choke! Didn't even make an adjustment to it.

[chris young]

If the whole thing got cleaned properly I would doubt that the idle circuit was plugged, just seemed to be the most obvious. You could have a vacuum leak, perhaps at the manifold since the carb has been off recently. You can check for that with a propane torch (not lit) by moving it around anywhere you may have a leak. If the engine picks up you have a leak. Again, if you use a vacuum gauge, you should be able to find out if you have leak as well. Spraying carb cleaner won't help the idle circuit.

I wouldn't trust the 1 1/2 turns thing either. It may be that that setting is quite a ways out and you really only have to adjust the idle screws properly. If you don't have a vacuum gauge you can at least adjust the idle screws by RPM and that may be all that's needed.

Moor makes a really good point about the choke as well. Mine will not idle low until the choke is open, it really needs to be adjusted and I haven't gotten to it on my own boat yet.

Good luck

[Moor]

I had a similar issue with my idle early in the season, all i had to do was adjust my choke. The P.O. had the carb rebuilt last year, apparently they never adjusted the choke properly. Hope thats all it needs. keep us posted

[86 century]

the one and a half turns is just a starting point.

you just haft to play with it mine was all jacked up when I got it.
After a couple of hours getting it perfect I have had people ask me if its fuel injected it starts so quick and idles smooth.

It is a holly though so things are subject to change with are temp and humidity.

[awesomesteven]

Ok, so I was able to manage to get the RPMs down to about 900. I ended up advancing the timing, although I'm not really sure how much since I didn't have my timing light on me, then i was able to bring the idle speed down.

[chris young]

did you adjust the idle mixture at all or just screwed down the curb idle after adjusting the timing?

[awesomesteven]

I adjusted both.